|**Pension Plans And Other Postretirement Benefits**            | 6 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          
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|**Pension Plans And Other Postretirement Benefits [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|Pension Plans And Other Postretirement Benefits                | Note 10 –Pension Plans and Other Postretirement Benefits
		
		The Company maintains a qualified defined benefit pension plan (the “Pension Plan”), a nonqualified pension plan, and other postretirement benefit plans for certain of its employees.  The net periodic benefit cost is based on estimated values and an extensive use of assumptions about the discount rate, expected return on plan assets, the rate of future compensation increases received by the Company’s employees, mortality, turnover, and medical costs.  The following tables provide the components of net periodic benefit cost:
		﻿﻿﻿
				
				Pension Benefits﻿
				
				Three Months Ended
				
				Six Months Ended﻿
				
				June 30,
				
				June 30,﻿
				
				2018
				
				2017
				
				2018
				
				2017﻿Service cost
				
				$
				812
				
				$
				794
				
				$
				1,625
				
				$
				1,587﻿Interest cost
				
				
				2,874
				
				
				3,108
				
				
				5,748
				
				
				6,217﻿Expected return on plan assets
				
				
				(4,553)
				
				
				(4,270)
				
				
				(9,106)
				
				
				(8,539)﻿Amortization of prior service cost
				
				
				132
				
				
				145
				
				
				264
				
				
				290﻿Amortization of actuarial loss
				
				
				1,823
				
				
				2,001
				
				
				3,646
				
				
				4,002﻿Net periodic benefit cost
				
				$
				1,088
				
				$
				1,778
				
				$
				2,177
				
				$
				3,557﻿﻿
				
				Other﻿
				
				Postretirement Benefits﻿
				
				
				Three Months Ended
				
				
				Six Months Ended﻿
				
				
				June 30,
				
				
				June 30,﻿
				
				2018
				
				2017
				
				2018
				
				2017﻿Service cost
				
				$
				262
				
				$
				255
				
				$
				525
				
				$
				510﻿Interest cost
				
				
				708
				
				
				737
				
				
				1,416
				
				
				1,473﻿Expected return on plan assets
				
				
				(677)
				
				
				(647)
				
				
				(1,353)
				
				
				(1,294)﻿Amortization of prior service cost
				
				
				(127)
				
				
				(127)
				
				
				(255)
				
				
				(254)﻿Amortization of actuarial loss
				
				
				296
				
				
				291
				
				
				591
				
				
				583﻿Net periodic benefit cost
				
				$
				462
				
				$
				509
				
				$
				924
				
				$
				1,018
		﻿
		The components of net periodic benefit cost other than service cost are presented on the consolidated statements of net income on the line item “Other.”
		﻿
		The Company made cash contributions of$8,627to its Pension Plan during the first six months of 2018, and intends to make additional cash contributions of$3,857to the Pension Plan during the remainder of 2018.
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|﻿Service cost                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|﻿Interest cost                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|﻿Expected return on plan assets                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|﻿Amortization of prior service cost                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|﻿Amortization of actuarial loss                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|﻿Net periodic benefit cost                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
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|﻿Expected return on plan assets                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|﻿Amortization of prior service cost                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|﻿Amortization of actuarial loss                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|﻿Net periodic benefit cost                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         

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