Investment Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Investment Securities
Total investment securities available-for-sale, Amortized Cost	$ 813,168	$ 781,232
Gross Unrealized Gains	15,879	13,955
Gross Unrealized Losses	(432)	(3,460)
Investment securities, available-for-sale	828,615	791,727
Contractual maturities of investments in debt securities available-for-sale, Amortized Cost
Due in one year or less	212,850
Due after one year through five years	320,672
Due after five years through ten years	38,732
Due after ten years	0
Mortgage-backed securities	239,486
Total debt securities available-for-sale	811,740
Contractual maturities of investments in debt securities available-for-sale, Fair Value
Due in one year or less	213,454
Due after one year through five years	324,588
Due after five years through ten years	39,207
Due after ten years	0
Mortgage-backed securities	244,170
Total debt securities available-for-sale	821,419
U.S. Treasury and Federal agencies securities
Investment Securities
Total investment securities available-for-sale, Amortized Cost	405,726	389,457
Gross Unrealized Gains	2,328	1,718
Gross Unrealized Losses	(59)	(1,506)
Investment securities, available-for-sale	407,995	389,669
U.S. States and political subdivisions securities
Investment Securities
Total investment securities available-for-sale, Amortized Cost	130,386	120,441
Gross Unrealized Gains	2,590	2,692
Gross Unrealized Losses	(147)	(143)
Investment securities, available-for-sale	132,829	122,990
Mortgage-backed securities - Federal agencies
Investment Securities
Total investment securities available-for-sale, Amortized Cost	239,486	234,400
Gross Unrealized Gains	4,884	3,430
Gross Unrealized Losses	(200)	(1,533)
Investment securities, available-for-sale	244,170	236,297
Corporate debt securities
Investment Securities
Total investment securities available-for-sale, Amortized Cost	35,342	34,241
Gross Unrealized Gains	288	199
Gross Unrealized Losses	(15)	(57)
Investment securities, available-for-sale	35,615	34,383
Foreign government and other securities
Investment Securities
Total investment securities available-for-sale, Amortized Cost	800	800
Gross Unrealized Gains	10	10
Gross Unrealized Losses	0	(1)
Investment securities, available-for-sale	810	809
Total debt securities
Investment Securities
Total investment securities available-for-sale, Amortized Cost	811,740	779,339
Gross Unrealized Gains	10,100	8,049
Gross Unrealized Losses	(421)	(3,240)
Investment securities, available-for-sale	821,419	784,148
Marketable equity securities
Investment Securities
Total investment securities available-for-sale, Amortized Cost	1,428	1,893
Gross Unrealized Gains	5,779	5,906
Gross Unrealized Losses	(11)	(220)
Investment securities, available-for-sale	$ 7,196	$ 7,579