Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net Income (Loss)	$ 457,251	$ (19,298)	$ 502,614	$ 120,461
Other comprehensive income (loss):
Total cash flow hedges	(3,525)	(5,220)	(8,560)	(28,831)
Pension and postretirement plans:
Amortization of net benefit obligation at transition, net of tax of ($1), $26, $6 and $77, respectively	(1)	48	11	143
Amortization of prior service cost, net of tax of $26, $28, $78 and $82, respectively	48	51	144	153
Amortization of net loss, including settlement charges, net of tax of $500, $729, $4,071 and $2,383, respectively	930	1,354	7,561	4,425
Current period change in fair value of pension and postretirement plans, net of tax of $190, $2,238, ($962) and $2,238, respectively	352	4,157	(1,784)	4,157
Total pension and postretirement plans	1,329	5,610	5,932	8,878
Comprehensive Income (Loss)	455,055	(18,908)	499,986	100,508
Commodity contracts
Other comprehensive income (loss):
Current period change in fair value of derivative commodity instruments, net of tax of $18, $42, $25, and ($6,669), respectively	29	69	40	(10,882)
Reclassification adjustment for derivative commodity instruments, net of tax of ($2,277), ($3,205), ($5,997) and ($11,486), respectively	(3,715)	(5,229)	(9,784)	(18,740)
Current period change in fair value of interest rate swap, net of tax of $0, ($188), ($160) and ($23), respectively	29	69	40	(10,882)
Reclassification adjustment for interest rate swap, net of tax of $86, $156, $798 and $449, respectively	(3,715)	(5,229)	(9,784)	(18,740)
Interest rate swap
Other comprehensive income (loss):
Current period change in fair value of derivative commodity instruments, net of tax of $18, $42, $25, and ($6,669), respectively	0	(350)	(298)	(42)
Reclassification adjustment for derivative commodity instruments, net of tax of ($2,277), ($3,205), ($5,997) and ($11,486), respectively	161	290	1,482	833
Current period change in fair value of interest rate swap, net of tax of $0, ($188), ($160) and ($23), respectively	0	(350)	(298)	(42)
Reclassification adjustment for interest rate swap, net of tax of $86, $156, $798 and $449, respectively	$ 161	$ 290	$ 1,482	$ 833