Deferred Tax Assets and Deferred Tax Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets
Allowance for loan and lease losses	$ 50,123	$ 50,013
Other real estate owned	8,380	8,200
Deferred compensation	8,166	5,024
Interest rate swap agreements	7,554	6,467
Acquisition fair market value adjustments	5,842	5,302
Income tax credits and net operating loss carryforwards	3,590	4,652
Employee benefits	3,165	2,839
Other	5,433	4,290
Total gross deferred tax assets	92,253	86,787
Deferred tax liabilities
Available-for-sale securities	(8,812)	(17,716)
Deferred loan costs	(7,427)	(6,419)
Intangibles	(6,272)	(4,290)
FHLB stock dividends	(4,601)	(10,342)
Depreciation of premises and equipment	(2,376)	(2,358)
Other	(4,290)	(3,925)
Total gross deferred tax liabilities	(33,778)	(45,050)
Net deferred tax asset	$ 58,475	$ 41,737