Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Consolidated Statements of Comprehensive Income [Abstract]
Net income	$ 323,770	$ 215,632	$ 149,296
Other comprehensive income (loss) before income taxes:
Net change in unrealized loss on available for sale securities and hedges	(52,757)	(425)	(57,346)
Reclassification of net losses realized and included in earnings	34,966	5,801	4,016
Valuation adjustment for pension plan amendment		17,315
Other valuation adjustments for employee benefit plan	45,198	10,929	12,748
Amortization of unrealized net loss on securities transferred to held to maturity	3,296	3,786	3,830
Other comprehensive income (loss) before income taxes	(59,693)	15,548	(62,248)
Income tax expense (benefit)	(13,386)	4,088	(22,311)
Other comprehensive income (loss) net of income taxes	(46,307)	11,460	(39,937)
Comprehensive income	$ 277,463	$ 227,092	$ 109,359