Securities, Securities in Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Securities [Abstract]
Percentage of total investment with unrealized losses	60.70%	65.60%
Available-for-sale, amortized cost [Abstract]
Less than 12 months	$ 316,117	$ 365,662
12 months or more	59,674	38,763
Total	375,791	404,425
Available-for-sale, gross unrealized losses [Abstract]
Less than 12 months	(3,584)	(5,586)
12 months or more	(1,158)	(1,193)
Total	(4,742)	(6,779)
Available-for-sale, fair value [Abstract]
Less than 12 months	312,533	360,076
12 months or more	58,516	37,570
Total	371,049	397,646
U.S. Treasury and Government Agencies [Member]
Available-for-sale, amortized cost [Abstract]
Less than 12 months	139,137	158,732
12 months or more	21,647	1,880
Total	160,784	160,612
Available-for-sale, gross unrealized losses [Abstract]
Less than 12 months	(419)	(716)
12 months or more	(41)	(27)
Total	(460)	(743)
Available-for-sale, fair value [Abstract]
Less than 12 months	138,718	158,016
12 months or more	21,606	1,853
Total	160,324	159,869
State and Political Subdivisions [Member]
Available-for-sale, amortized cost [Abstract]
Less than 12 months	26,970	53,491
12 months or more	2,383	751
Total	29,353	54,242
Available-for-sale, gross unrealized losses [Abstract]
Less than 12 months	(742)	(1,780)
12 months or more	(21)	(12)
Total	(763)	(1,792)
Available-for-sale, fair value [Abstract]
Less than 12 months	26,228	51,711
12 months or more	2,362	739
Total	28,590	52,450
U.S. Government Sponsored Agency Mortgage-backed Securities [Member]
Available-for-sale, amortized cost [Abstract]
Less than 12 months	132,510	135,939
12 months or more	30,644	31,132
Total	163,154	167,071
Available-for-sale, gross unrealized losses [Abstract]
Less than 12 months	(2,076)	(2,646)
12 months or more	(849)	(880)
Total	(2,925)	(3,526)
Available-for-sale, fair value [Abstract]
Less than 12 months	130,434	133,293
12 months or more	29,795	30,252
Total	160,229	163,545
Debt Securities [Member]
Available-for-sale, amortized cost [Abstract]
Less than 12 months	298,617	348,162
12 months or more	54,674	33,763
Total	353,291	381,925
Available-for-sale, gross unrealized losses [Abstract]
Less than 12 months	(3,237)	(5,142)
12 months or more	(911)	(919)
Total	(4,148)	(6,061)
Available-for-sale, fair value [Abstract]
Less than 12 months	295,380	343,020
12 months or more	53,763	32,844
Total	349,143	375,864
CRA Investments Funds [Member]
Available-for-sale, amortized cost [Abstract]
Less than 12 months	17,500	17,500
12 months or more	5,000	5,000
Total	22,500	22,500
Available-for-sale, gross unrealized losses [Abstract]
Less than 12 months	(347)	(444)
12 months or more	(247)	(274)
Total	(594)	(718)
Available-for-sale, fair value [Abstract]
Less than 12 months	17,153	17,056
12 months or more	4,753	4,726
Total	$ 21,906	$ 21,782
Severity of impairment in percentage of fair value less than cost	2.40%