CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Parent [Line Items]
Net income (loss)	$ 107,592	$ 167,475
Other comprehensive income (loss):
Net unrealized gain (loss) from pension and postretirement plans, net of tax	(209)	347
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax	347	(107)
Amortization Of Financing Cash Flow Hedge Contracts To Earnings During Period Net Of Tax	94	854
Other comprehensive income (loss)	232	1,094
Comprehensive income (loss)	107,824	168,569
Subsidiaries [Member]
Parent [Line Items]
Net income (loss)	121,083	179,938
Other comprehensive income (loss):
Net unrealized gain (loss) from pension and postretirement plans, net of tax	2,001	3,386
Other Comprehensive Income (Loss), Reclassification Adjustment on Derivatives Included in Net Income, Net of Tax	718	1,811
Amortization Of Financing Cash Flow Hedge Contracts To Earnings During Period Net Of Tax	79	79
Other comprehensive income (loss)	2,798	5,276
Comprehensive income (loss)	$ 123,881	$ 185,214