Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Consolidated Statements of Comprehensive Income [Abstract]
Net income	$ 71,177	$ 52,267	$ 143,652	$ 101,281
Other comprehensive income/loss before income taxes:
Net change in unrealized gain/loss on securities available for sale and cash flow hedges	(23,409)	12,661	(85,653)	13,845
Reclassification of net losses realized and included in earnings	2,217	1,718	4,013	3,105
Valuation adjustment for pension plan amendment		17,315		17,315
Other Valuation adjustment for employee benefit plans	(9,039)	(10,782)	(9,039)	(10,782)
Amortization of unrealized net loss on securities transferred to held to maturity	925	1,099	1,680	1,749
Other comprehensive income/loss before income taxes	(29,306)	22,011	(88,999)	25,232
Income tax expense (benefit)	(6,646)	7,938	(20,192)	9,139
Other comprehensive income/loss net of income taxes	(22,660)	14,073	(68,807)	16,093
Comprehensive income	$ 48,517	$ 66,340	$ 74,845	$ 117,374