Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Net Income (Loss)	$ (227,904)	$ 457,251	$ (354,925)	$ 502,614
Other comprehensive income (loss):
Total cash flow hedges	0	(3,525)	0	(8,560)
Pension and postretirement plans:
Amortization of net benefit obligation at transition, net of tax of $0, ($1), $0 and $6, respectively	0	(1)	0	11
Amortization of prior service cost, net of tax of $0, $26, $0 and $78, respectively	0	48	0	144
Amortization of net loss, including settlement charges, net of tax of $256, $500, $1,561 and $4,071, respectively	474	930	2,901	7,561
Current period change in fair value of pension and postretirement plans, net of tax of $0, $190, $0 and ($962), respectively	0	352	0	(1,784)
Total pension and postretirement plans	474	1,329	2,901	5,932
Comprehensive Income (Loss)	(227,430)	455,055	(352,024)	499,986
Commodity contracts
Other comprehensive income (loss):
Current period change in fair value of derivative commodity instruments, net of tax	0	29	0	40
Reclassification adjustment for derivative commodity instruments, net of tax	0	(3,715)	0	(9,784)
Interest rate swap
Other comprehensive income (loss):
Current period change in fair value of derivative commodity instruments, net of tax	0	0	0	(298)
Reclassification adjustment for derivative commodity instruments, net of tax	$ 0	$ 161	$ 0	$ 1,482