Investment Securities (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Investment Securities
Investment securities available-for-sale, Amortized Cost	$ 822,163	$ 849,139
Available-for-sale Securities, Gross Unrealized Gain	19,480	32,313
Available-for-sale Securities, Gross Unrealized Loss	(8,943)	(688)
Investment securities, available-for-sale	832,700	880,764
Contractual maturities of debt securities available-for-sale, Amortized Cost
Due in one year or less	143,994
Due after one year through five years	340,277
Due after five years through ten years	62,231
Due after ten years	0
Total debt securities available-for-sale	819,997
Contractual maturities of debt securities available-for-sale, Fair Value
Due in one year or less	143,373
Due after one year through five years	345,292
Due after five years through ten years	61,387
Due after ten years	0
Total debt securities available-for-sale	825,132
Gross realized gains and losses
Gross realized gains	903	282	1,662
Gross realized losses	(1,071)	0	(284)
Net realized gains (losses)	(168)	282	1,378
U.S. Treasury and Federal agencies securities
Investment Securities
Investment securities available-for-sale, Amortized Cost	394,558	410,983
Available-for-sale Securities, Gross Unrealized Gain	5,008	11,353
Available-for-sale Securities, Gross Unrealized Loss	(4,527)	(83)
Investment securities, available-for-sale	395,039	422,253
U.S. States and political subdivisions securities
Investment Securities
Investment securities available-for-sale, Amortized Cost	120,416	100,055
Available-for-sale Securities, Gross Unrealized Gain	3,670	5,864
Available-for-sale Securities, Gross Unrealized Loss	(847)	(482)
Investment securities, available-for-sale	123,239	105,437
Mortgage-backed securities - Federal agencies
Investment Securities
Investment securities available-for-sale, Amortized Cost	273,495	301,136
Available-for-sale Securities, Gross Unrealized Gain	5,148	11,296
Available-for-sale Securities, Gross Unrealized Loss	(3,563)	(25)
Investment securities, available-for-sale	275,080	312,407
Corporate debt securities
Investment Securities
Investment securities available-for-sale, Amortized Cost	30,828	30,897
Available-for-sale Securities, Gross Unrealized Gain	241	445
Available-for-sale Securities, Gross Unrealized Loss	(4)	(94)
Investment securities, available-for-sale	31,065	31,248
Foreign government and other securities
Investment Securities
Investment securities available-for-sale, Amortized Cost	700	3,700
Available-for-sale Securities, Gross Unrealized Gain	9	26
Available-for-sale Securities, Gross Unrealized Loss	0	0
Investment securities, available-for-sale	709	3,726
Total debt securities
Investment Securities
Investment securities available-for-sale, Amortized Cost	819,997	846,771
Available-for-sale Securities, Gross Unrealized Gain	14,076	28,984
Available-for-sale Securities, Gross Unrealized Loss	(8,941)	(684)
Investment securities, available-for-sale	825,132	875,071
Marketable equity securities
Investment Securities
Investment securities available-for-sale, Amortized Cost	2,166	2,368
Available-for-sale Securities, Gross Unrealized Gain	5,404	3,329
Available-for-sale Securities, Gross Unrealized Loss	(2)	(4)
Investment securities, available-for-sale	$ 7,568	$ 5,693