Consolidated Statement of Other Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 258,626	$ 243,194	$ 216,612
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent	(1,327)	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	245	0	0
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, before Tax	(4,399)	(1,407)	(8,956)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost (Credit), Tax	1,024	583	0
Defined Benefit Plan, Amortization of Transition Obligations (Assets)	(87)	(87)	(87)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	7	159	159
Defined Benefit Plan, Amortization of Gains (Losses)	540	468	0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax	729	71	2,210
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	255,358	242,981	209,938
Net Income (Loss) Attributable to Noncontrolling Interest	1,141	383	541
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 254,217	$ 242,598	$ 209,397