|**Net Income Per Share (Tables)**                        | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|-------------------------------------------------------- | -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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|**Earnings Per Share [Abstract]**                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Reconciliation of Basic and Diluted Net Income Per Share | The following table reconciles basic and diluted net income per share for the years indicated:201620152014Weighted-Average SharesWeighted-Average SharesWeighted-Average SharesBasic net income per share:Net income available to common stockholders$81,05140,767,343$1.99$65,38437,816,399$1.73$60,16236,266,356$1.66Effect of dilutive stock options and warrants245,790271,834288,253Diluted net income per share:Net income available to common stockholders$81,05141,013,133$1.98$65,38438,088,233$1.72$60,16236,554,609$1.65
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|                                                         | 2016                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               
|                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Basic net income per share:                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Net income available to common stockholders              | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
|Effect of dilutive stock options and warrants            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Diluted net income per share:                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Net income available to common stockholders              | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  

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duration X- DefinitionTabular disclosure of an entity's basic and diluted earnings per share calculations, including a reconciliation of numerators and denominators of the basic and diluted per-share computations for income from continuing operations.
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