Accumulated Other Comprehensive Income (Loss) - Reclassifications out of AOCI - (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Reclassifications out of accumulated other comprehensive income, net of tax
Interest expense	$ (2,036)	$ (2,547)	$ (6,229)	$ (7,984)
Other noninterest income	1,194	1,245	5,032	3,970
Provision for income taxes	(14,387)	(13,377)	(39,368)	(38,515)
Net income	28,095	25,140	77,105	73,938
Amount Reclassified from Accumulated Other Comprehensive Loss
Reclassifications out of accumulated other comprehensive income, net of tax
Net income	168	194	433	560
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	69	89	209	230
Provision for income taxes	(27)	(34)	(80)	(88)
Net income	42	55	129	142
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			(122)
Provision for income taxes			47
Net income			(75)
Amortization of defined benefit pension | Amount Reclassified from Accumulated Other Comprehensive Loss
Reclassifications out of accumulated other comprehensive income, net of tax
Salaries and employee benefits	204	225	612	674
Provision for income taxes	(78)	(86)	(233)	(256)
Net income	$ 126	$ 139	$ 379	$ 418