Consolidated Statement of Other Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 114,932	$ 258,626	$ 243,194
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax	(1,471)	(1,327)	0
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent	83	(1,082)	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	971	245	0
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax	583	0	0
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax	1,151	(4,399)	(1,407)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost (Credit), Tax	0	1,024	583
Defined Benefit Plan, Amortization of Transition Obligations (Assets)	(96)	(87)	(87)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(85)	7	159
Defined Benefit Plan, Amortization of Gains (Losses)	727	540	468
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax	(424)	729	71
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	122	1,189	611
Other Comprehensive Income (Loss), Net of Tax	1,356	(3,268)	(213)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	116,288	255,358	242,981
Net Income (Loss) Attributable to Noncontrolling Interest	85	1,141	383
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 116,203	$ 254,217	$ 242,598