Investment Securities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Investment Securities
Available-for-sale Securities, Amortized Cost Basis	$ 781,232	$ 776,057
Available-for-sale Securities, Gross Unrealized Gain	13,955	18,052
Available-for-sale Securities, Gross Unrealized Loss	(3,460)	(2,991)
Investment securities, available-for-sale	791,727	791,118
Contractual maturities of debt securities available-for-sale, Amortized Cost
Due in one year or less	83,635
Due after one year through five years	442,622
Due after five years through ten years	18,682
Due after ten years	0
Mortgage-backed securities	234,400
Total debt securities available-for-sale	779,339
Contractual maturities of debt securities available-for-sale, Fair Value
Due in one year or less	84,161
Due after one year through five years	444,585
Due after five years through ten years	19,105
Due after ten years	0
Mortgage-backed securities	236,297
Total debt securities available-for-sale	784,148
Gross realized gains and losses
Gross realized gains	4	963	$ 903
Gross realized losses	0	0	(1,071)
Net realized gains (losses)	4	963	$ (168)
U.S. Treasury and Federal agencies securities
Investment Securities
Available-for-sale Securities, Amortized Cost Basis	389,457	371,878
Available-for-sale Securities, Gross Unrealized Gain	1,718	3,593
Available-for-sale Securities, Gross Unrealized Loss	(1,506)	(1,968)
Investment securities, available-for-sale	389,669	373,503
U.S. States and political subdivisions securities
Investment Securities
Available-for-sale Securities, Amortized Cost Basis	120,441	121,510
Available-for-sale Securities, Gross Unrealized Gain	2,692	3,392
Available-for-sale Securities, Gross Unrealized Loss	(143)	(214)
Investment securities, available-for-sale	122,990	124,688
Mortgage-backed securities - Federal agencies
Investment Securities
Available-for-sale Securities, Amortized Cost Basis	234,400	248,299
Available-for-sale Securities, Gross Unrealized Gain	3,430	5,490
Available-for-sale Securities, Gross Unrealized Loss	(1,533)	(781)
Investment securities, available-for-sale	236,297	253,008
Corporate debt securities
Investment Securities
Available-for-sale Securities, Amortized Cost Basis	34,241	31,677
Available-for-sale Securities, Gross Unrealized Gain	199	281
Available-for-sale Securities, Gross Unrealized Loss	(57)	(26)
Investment securities, available-for-sale	34,383	31,932
Foreign government and other securities
Investment Securities
Available-for-sale Securities, Amortized Cost Basis	800	800
Available-for-sale Securities, Gross Unrealized Gain	10	11
Available-for-sale Securities, Gross Unrealized Loss	(1)	0
Investment securities, available-for-sale	809	811
Total debt securities
Investment Securities
Available-for-sale Securities, Amortized Cost Basis	779,339	774,164
Available-for-sale Securities, Gross Unrealized Gain	8,049	12,767
Available-for-sale Securities, Gross Unrealized Loss	(3,240)	(2,989)
Investment securities, available-for-sale	784,148	783,942
Marketable equity securities
Investment Securities
Available-for-sale Securities, Amortized Cost Basis	1,893	1,893
Available-for-sale Securities, Gross Unrealized Gain	5,906	5,285
Available-for-sale Securities, Gross Unrealized Loss	(220)	(2)
Investment securities, available-for-sale	$ 7,579	$ 7,176