Consolidated Condensed Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net Income	$ 2,046	$ 87,599	$ 190,739	$ 245,192
Other Comprehensive Income (Loss):
Current period change in fair value of commodity derivative instruments, net of tax of ($30,622), $105,683, $30,621 and $76,616	(49,962)	172,430	49,961	125,005
Pension and postretirement plans:
Amortization of net obligation at transition, net of taxes of $25, $24, $75 and $72	47	44	140	133
Amortization of prior service cost, net of taxes of $30, $26, $89 and $78	55	48	166	145
Amortization of net loss, net of taxes of $413, $318, $1,238 and $953	766	591	2,300	1,770
Current period change in fair value of pension and postretirement plans, net of taxes of ($4,073) ($5,988), ($4,073) and ($5,988)	(7,564)	(11,121)	(7,564)	(11,121)
Total pension and postretirement plans	(6,696)	(10,438)	(4,958)	(9,073)
Current period change in fair value of interest rate swap, net of tax ($375) and ($1,205)	(697)	0	(2,240)	0
Comprehensive Income (Loss)	498,907	561,987	561,987	351,039
Commodity Contract [Member]
Other Comprehensive Income (Loss):
Reclassification adjustment for derivative instruments, net of tax	(8,034)	(10,440)	(23,337)	(10,085)
Interest Rate Swap [Member]
Other Comprehensive Income (Loss):
Reclassification adjustment for derivative instruments, net of tax	$ 263	$ 0	$ 783	$ 0