CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)
Net income (loss)	$ 185,867		$ (54,053)		$ 559,013		$ (351,481)
Change in derivatives:
Settlements	(55,968)	[1]	(94,996)	[1]	(130,942)	[1]	(310,882)	[1]
Ineffectiveness	872	[2]	322	[2]	1,310	[2]	(1,215)	[2]
Change in fair value of derivative instruments	7,509	[3]	(36,468)	[3]	29,600	[3]	93,985	[3]
Total change in derivatives	(47,587)		(131,142)		(100,032)		(218,112)
Change in value of pension and other postretirement liabilities:
Amortization of prior service cost included in net periodic pension cost	266	[4]	254	[4]	800	[4]	762	[4]
Change in currency translation adjustment	633		997		(1,814)		962
Comprehensive income (loss)	$ 139,179		$ (183,944)		$ 457,967		$ (567,869)

[1] Net of ($37.3), ($62.2), ($87.3) and ($202.6) million in taxes for the three months ended September 30, 2013 and 2012, and nine months ended September 30, 2013 and 2012, respectively.

[2] Net of $0.6, $0.2, $0.9 and ($0.8) million in taxes for the three months ended September 30, 2013 and 2012, and nine months ended September 30, 2013 and 2012, respectively.

[3] Net of $5.0, ($22.1), $19.7, and $62.7 million in taxes for the three months ended September 30, 2013 and 2012, and nine months ended September 30, 2013 and 2012, respectively.

[4] Net of $0.2, $0.2, $0.5, and $0.5 million in taxes for the three months ended September 30, 2013 and 2012, and nine months ended September 30, 2013 and 2012, respectively.