| **Comprehensive Income (Accumulated Other Comprehensive Loss, Net of Tax) (Details) (USD $)In Thousands, unless otherwise specified** | 12 Months Ended |
|---------------------------------------------------------------------------------------------------------------------------------------|-----------------|
||
| **Accumulated Other Comprehensive Income (Loss) [Line Items]**                                                                        |            |   |   |
| Balance, beginning                                                                                                                    | $ (483,576)     | $ (386,963) | $ (229,549) |
| Other comprehensive income before reclassifications                                                                                   | 171,681         | (113,453) | (163,236) |
| Amounts reclassified from accumulated other comprehensive loss                                                                        | 23,984          | 16,840 | 5,822 |
| Recognition of net actuarial loss for pension settlement costs                                                                        | 27,381          |   |   |
| Net current-period other comprehensive income (loss)                                                                                  | 223,046         | (96,613) | (157,414) |
| Balance, ending                                                                                                                       | (260,530)       | (483,576) | (386,963) |
| Pension Benefits [Member]                                                                                                             |            |   |   |
| **Accumulated Other Comprehensive Income (Loss) [Line Items]**                                                                        |            |   |   |
| Balance, beginning                                                                                                                    | (697,874)       | (575,163) | (349,264) |
| Other comprehensive income before reclassifications                                                                                   | 205,341         | (152,402) | (241,064) |
| Amounts reclassified from accumulated other comprehensive loss                                                                        | 36,938          | 29,691 | 15,165 |
| Recognition of net actuarial loss for pension settlement costs                                                                        | 44,163          |   |   |
| Net current-period other comprehensive income (loss)                                                                                  | 286,442         | (122,711) | (225,899) |
| Balance, ending                                                                                                                       | (411,432)       | (697,874) | (575,163) |
| Postretirement Costs [Member]                                                                                                         |            |   |   |
| **Accumulated Other Comprehensive Income (Loss) [Line Items]**                                                                        |            |   |   |
| Balance, beginning                                                                                                                    | (74,264)        | (41,811) | (13,369) |
| Other comprehensive income before reclassifications                                                                                   | 67,289          | (29,922) | (22,668) |
| Amounts reclassified from accumulated other comprehensive loss                                                                        | 1,745           | (2,531) | (5,774) |
| Net current-period other comprehensive income (loss)                                                                                  | 69,034          | (32,453) | (28,442) |
| Balance, ending                                                                                                                       | (5,230)         | (74,264) | (41,811) |
| Deferred Taxes On Pension And OPEB Costs [Member]                                                                                     |            |   |   |
| **Accumulated Other Comprehensive Income (Loss) [Line Items]**                                                                        |            |   |   |
| Balance, beginning                                                                                                                    | 288,712         | 230,161 | 132,752 |
| Other comprehensive income before reclassifications                                                                                   | (100,951)       | 68,871 | 100,978 |
| Amounts reclassified from accumulated other comprehensive loss                                                                        | (14,699)        | (10,320) | (3,569) |
| Recognition of net actuarial loss for pension settlement costs                                                                        | (16,782)        |   |   |
| Net current-period other comprehensive income (loss)                                                                                  | (132,432)       | 58,551 | 97,409 |
| Balance, ending                                                                                                                       | 156,280         | 288,712 | 230,161 |
| All Other [Member]                                                                                                                    |            |   |   |
| **Accumulated Other Comprehensive Income (Loss) [Line Items]**                                                                        |            |   |   |
| Balance, beginning                                                                                                                    | (150)           | (150) | 332 |
| Other comprehensive income before reclassifications                                                                                   | 2               |    | (482) |
| Amounts reclassified from accumulated other comprehensive loss                                                                        |            |    |   |
| Net current-period other comprehensive income (loss)                                                                                  | 2               |    | (482) |
| Balance, ending                                                                                                                       | $ (148)         | $ (150) | $ (150) |

| X                                                                                                                                                                                                                                                                                                                                                                                   |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Other comprehensive income, Recognition of net actuarial loss for pension settlement costs, before tax
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount before tax of increase (decrease) in accumulated in equity from transactions and other events and circumstances from non-owner sources. Excludes net income (loss), and accumulated changes in equity from transactions resulting from investments by owners (distributions to owners).
+ References
No definition available.
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| X                                                                                                                                                                                    |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount before tax and reclassification adjustments of other comprehensive income (loss).
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount before tax, after reclassification adjustments of other comprehensive income (loss).
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=28358780&loc=SL7669619-108580Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=28358780&loc=SL7669625-108580Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33775-111570
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| X                                                                                                                                                                                                                                                                                                                                                                 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount before tax of reclassification adjustments of other comprehensive income (loss).
+ References
No definition available.
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