Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Consolidated Statements of Comprehensive Income [Abstract]
Net income	$ 149,296	$ 131,461	$ 175,722
Other comprehensive income before income taxes
Net change in unrealized (loss) gain on available for sale securities and hedges	(57,346)	(21,270)	14,821
Reclassification of net (gain) losses realized and included in earnings	4,016	3,010	390
Valuation adjustment for employee benefit plans	(12,748)	(33,971)	(41,244)
Amortization of unrealized net loss on securities transferred to held to maturity	3,830	3,530	3,297
Other comprehensive loss before income taxes	(62,248)	(48,701)	(22,736)
Income tax benefit	(22,311)	(18,180)	(8,041)
Other comprehensive loss net of income taxes	(39,937)	(30,521)	(14,695)
Comprehensive income	$ 109,359	$ 100,940	$ 161,027