Consolidated Statement of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net Income (Loss)	$ 163,090	$ 659,056	$ 388,073
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax, Portion Attributable to Parent	94,989	456,493	129,231
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	97,316	45,631	114,240
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred	(18,288)	(79,899)	(189,259)
Other Comprehensive Income (Loss), Net of Tax	174,017	422,225	54,212
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	337,107	1,081,281	442,285
Less: Comprehensive Loss (Income), Net of Tax, Attributable to Noncontrolling Interest	0	(1,386)	(397)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 337,107	$ 1,082,667	$ 442,682