Investment Securities (Available-for-sale Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities
Amortized Cost	$ 780,609	$ 632,967
Gross Unrealized Gains	17,652	12,693
Gross Unrealized Losses	(4,976)	(8,780)
Available-for-sale securities	793,285	636,880
U.S. Treasury and government agencies
Schedule of Available-for-sale Securities
Amortized Cost	0	1
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Available-for-sale securities	0	1
U.S. government sponsored agencies
Schedule of Available-for-sale Securities
Amortized Cost	2,904	5,836
Gross Unrealized Gains	89	114
Gross Unrealized Losses	0	0
Available-for-sale securities	2,993	5,950
States and political subdivisions
Schedule of Available-for-sale Securities
Amortized Cost	112,132	62,292
Gross Unrealized Gains	3,196	2,510
Gross Unrealized Losses	(79)	(59)
Available-for-sale securities	115,249	64,743
Residential mortgage-backed securities
Schedule of Available-for-sale Securities
Amortized Cost	634,892	529,245
Gross Unrealized Gains	8,836	5,910
Gross Unrealized Losses	(4,401)	(7,864)
Available-for-sale securities	639,327	527,291
Commercial mortgage-backed securities
Schedule of Available-for-sale Securities
Amortized Cost	23,930	28,021
Gross Unrealized Gains	418	112
Gross Unrealized Losses	0	(286)
Available-for-sale securities	24,348	27,847
Bank-issued trust preferred securities
Schedule of Available-for-sale Securities
Amortized Cost	5,140	6,132
Gross Unrealized Gains	42	3
Gross Unrealized Losses	(406)	(490)
Available-for-sale securities	4,776	5,645
Equity securities
Schedule of Available-for-sale Securities
Amortized Cost	1,611	1,440
Gross Unrealized Gains	5,071	4,044
Gross Unrealized Losses	(90)	(81)
Available-for-sale securities	$ 6,592	$ 5,403