Accumulated Other Comprehensive Income (Loss) - Reclassifications out of AOCI - (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Reclassifications out of accumulated other comprehensive income, net of tax
Interest expense	$ (3,748)	$ (1,980)	$ (7,372)	$ (4,194)
Other noninterest income	1,491	2,473	3,165	3,838
Provision for income taxes	(15,930)	(12,420)	(23,033)	(24,981)
Net income	31,823	24,516	50,087	49,010
Amount Reclassified from Accumulated Other Comprehensive Loss
Reclassifications out of accumulated other comprehensive income, net of tax
Net income	61	168	269	264
Gains and Losses on Cash Flow Hedges
Reclassifications out of accumulated other comprehensive income, net of tax
Amounts reclassified from accumulated other comprehensive income (loss)	(12)	(42)	(104)	(88)
Gains and Losses on Cash Flow Hedges | Amount Reclassified from Accumulated Other Comprehensive Loss | Interest rate contracts
Reclassifications out of accumulated other comprehensive income, net of tax
Interest expense	19	68	168	142
Provision for income taxes	(7)	(26)	(64)	(54)
Net income	12	42	104	88
Unrealized gain and losses on sales of available for sale securities
Reclassifications out of accumulated other comprehensive income, net of tax
Amounts reclassified from accumulated other comprehensive income (loss)	67		68	76
Unrealized gain and losses on sales of available for sale securities | Amount Reclassified from Accumulated Other Comprehensive Loss
Reclassifications out of accumulated other comprehensive income, net of tax
Other noninterest income	(110)		(110)	(122)
Provision for income taxes	43		42	46
Net income	(67)		(68)	(76)
Benefit plans
Reclassifications out of accumulated other comprehensive income, net of tax
Amounts reclassified from accumulated other comprehensive income (loss)	(116)	(126)	(233)	(252)
Benefit plans | Amount Reclassified from Accumulated Other Comprehensive Loss
Reclassifications out of accumulated other comprehensive income, net of tax
Salaries and employee benefits	187	204	376	408
Provision for income taxes	(71)	(78)	(143)	(156)
Net income	$ 116	$ 126	$ 233	$ 252