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Pension and OPEB - Periodic Cost (Details) (USD $)
In Thousands, unless otherwise specified |
3 Months Ended | 6 Months Ended | 3 Months Ended | 6 Months Ended | 3 Months Ended | 6 Months Ended | 3 Months Ended | 6 Months Ended | 12 Months Ended | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Jun. 30, 2013
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Jun. 30, 2012
|
Jun. 30, 2013
|
Jun. 30, 2012
|
Dec. 31, 2012
|
Jun. 30, 2013
Pension Plans, Defined Benefit [Member]
|
Jun. 30, 2012
Pension Plans, Defined Benefit [Member]
|
Jun. 30, 2013
Pension Plans, Defined Benefit [Member]
|
Jun. 30, 2012
Pension Plans, Defined Benefit [Member]
|
Jun. 30, 2013
Other Postretirement Benefit Plans, Defined Benefit [Member]
|
Jun. 30, 2012
Other Postretirement Benefit Plans, Defined Benefit [Member]
|
Jun. 30, 2013
Other Postretirement Benefit Plans, Defined Benefit [Member]
|
Jun. 30, 2012
Other Postretirement Benefit Plans, Defined Benefit [Member]
|
Jun. 30, 2013
Change in Assumptions for Pension Plans [Member]
Pension Plans, Defined Benefit [Member]
Rate
|
Mar. 31, 2013
Change in Assumptions for Pension Plans [Member]
Pension Plans, Defined Benefit [Member]
|
Jun. 30, 2013
Change in Assumptions for Pension Plans [Member]
Pension Plans, Defined Benefit [Member]
Rate
|
Dec. 31, 2012
Change in Assumptions for Pension Plans [Member]
Pension Plans, Defined Benefit [Member]
Rate
|
|
| Defined Benefit Plan, Net Periodic Benefit Cost [Abstract] | |||||||||||||||||
| Service cost | $ 5,581 | $ 4,850 | $ 11,287 | $ 10,003 | $ 4,849 | $ 4,566 | $ 9,698 | $ 9,766 | |||||||||
| Interest cost | 8,909 | 9,415 | 17,752 | 18,793 | 29,619 | 32,795 | 59,237 | 68,322 | |||||||||
| Expected return on plan assets | (12,711) | (11,452) | (24,855) | (23,079) | 0 | 0 | 0 | 0 | |||||||||
| Defined Benefit Plan, Amortization of Prior Service Cost (Credit) | (8,211) | (13,915) | (16,423) | (26,021) | (407) | (407) | (815) | (815) | (7,804) | (13,410) | (15,608) | (25,009) | |||||
| Amortization of actuarial gain | (23,559) | (26,072) | (48,747) | (53,077) | 10,547 | 11,654 | 22,722 | 23,917 | 17,595 | 20,020 | 35,190 | 40,365 | |||||
| Other Comprehensive Income (Loss), Finalization of Pension and Non-Pension Postretirement Plan Valuation, Net of Tax | 5,087 | (32,202) | 5,087 | 0 | 32,202 | 0 | 0 | 0 | 0 | 0 | |||||||
| Net periodic (benefit) cost | 20,435 | 12,157 | 64,526 | 27,056 | 17,006 | 14,060 | 58,293 | 28,819 | 44,259 | 43,971 | 88,517 | 93,444 | 10,960 | ||||
| Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate | 4.84% | 4.12% | 4.00% | ||||||||||||||
| Pension Contributions | 34,376 | ||||||||||||||||
| Total anticipated contributions to pension trust | 50,000 | ||||||||||||||||
| Defined Benefit Plan, Plan Amendments | 48,957 | 29,916 | |||||||||||||||
| Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax | (42,904) | (7,586) | (88,661) | (67,159) | 33,414 | 35,261 | |||||||||||
| Deferred Income Taxes | 143,004 | 143,004 | 148,104 | 20,630 | 21,770 | 20,630 | |||||||||||
| Defined Benefit Plan, Benefits Paid | $ 83,106 | ||||||||||||||||