Securities, Amortized Cost and Fair Value of Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Available-for-sale debt securities [Abstract]
Amortized cost	$ 546,539	$ 613,395
Gross unrealized gains	7,181	7,358
Gross unrealized losses	(2,035)	(5,456)
Fair value	551,685	615,297
Available-for-sale [Abstract]
Amortized cost	571,539	638,395
Gross unrealized gains	7,209	7,358
Gross unrealized losses	(2,035)	(5,567)
Fair value	576,713	640,186
Held-to-maturity [Abstract]
Amortized cost	1,661	1,662
Gross unrealized gains	1	1
Gross unrealized losses	(11)	(19)
Fair value	1,651	1,644
U.S. Treasury and Government Agencies [Member]
Available-for-sale debt securities [Abstract]
Amortized cost	201,461	190,563
Gross unrealized gains	990	509
Gross unrealized losses	(401)	(2,140)
Fair value	202,050	188,932
State and Political Subdivisions [Member]
Available-for-sale debt securities [Abstract]
Amortized cost	132,249	133,951
Gross unrealized gains	3,718	3,973
Gross unrealized losses	(508)	(466)
Fair value	135,459	137,458
U.S. Government Sponsored Agency Mortgage-backed Securities [Member]
Available-for-sale debt securities [Abstract]
Amortized cost	212,829	288,881
Gross unrealized gains	2,473	2,876
Gross unrealized losses	(1,126)	(2,850)
Fair value	214,176	288,907
CRA Investments Funds [Member]
Available-for-sale equity securities [Abstract]
Amortized cost	25,000	25,000
Gross unrealized gains	28	0
Gross unrealized losses	0	(111)
Fair value	25,028	24,889
U.S. Treasury and Government Agencies [Member]
Held-to-maturity [Abstract]
Amortized cost	480	480
Gross unrealized gains	0	0
Gross unrealized losses	(11)	(19)
Fair value	469	461
State and Political Subdivisions [Member]
Held-to-maturity [Abstract]
Amortized cost	1,181	1,182
Gross unrealized gains	1	1
Gross unrealized losses	0	0
Fair value	$ 1,182	$ 1,183