Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net unrealized gain (loss) on cash flow hedges, tax	$ 484	$ 1,080	$ 894
Net unrealized loss on investment securities, tax	(1,427)	2,775	(3,689)
Adjustments to pension and postretirement plans, tax	13,844	(106,336)	64,316
Amortization of pension and postretirement costs, tax	$ 15,966	$ 15,643	$ 19,228