CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
NET INCOME (LOSS)	$ 32,836	$ (481)
Derivative instruments:
Net unrealized gain (loss), net of tax benefit (expense) of ($38) and $16,551	58	(25,352)
Reclassification of net realized loss, net of tax benefit of $3,300 and $5,728	5,053	8,772
Pension and other postretirement benefits activity, net of tax expense of $631 and $631	966	966
Total other comprehensive income (loss)	6,077	(15,614)
COMPREHENSIVE INCOME (LOSS)	38,913	(16,095)
Less: Comprehensive income attributable to noncontrolling interests	8,392	7,776
COMPREHENSIVE INCOME (LOSS) ATTRIBUTABLE TO COMMON SHAREHOLDERS	$ 30,521	$ (23,871)