Securities, Amortized Cost and Fair Value of Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Available-for-sale debt securities [Abstract]
Amortized cost	$ 586,178	$ 583,939
Gross unrealized gains	3,842	3,158
Gross unrealized losses	(4,148)	(6,061)
Fair value	585,872	581,036
Available-for-sale [Abstract]
Amortized cost	611,178	608,939
Gross unrealized gains	3,932	3,234
Gross unrealized losses	(4,742)	(6,779)
Fair value	610,368	605,394
Held-to-maturity [Abstract]
Amortized cost	858	866
Gross unrealized gains	0	1
Gross unrealized losses	0	0
Fair value	858	867
U.S. Treasury and Government Agencies [Member]
Available-for-sale debt securities [Abstract]
Amortized cost	236,345	223,014
Gross unrealized gains	173	193
Gross unrealized losses	(460)	(743)
Fair value	236,058	222,464
State and Political Subdivisions [Member]
Available-for-sale debt securities [Abstract]
Amortized cost	129,872	133,351
Gross unrealized gains	2,833	1,957
Gross unrealized losses	(763)	(1,792)
Fair value	131,942	133,516
U.S. Government Sponsored Agency Mortgage-backed Securities [Member]
Available-for-sale debt securities [Abstract]
Amortized cost	219,961	227,574
Gross unrealized gains	836	1,008
Gross unrealized losses	(2,925)	(3,526)
Fair value	217,872	225,056
CRA Investments Funds [Member]
Available-for-sale equity securities [Abstract]
Amortized cost	25,000	25,000
Gross unrealized gains	90	76
Gross unrealized losses	(594)	(718)
Fair value	24,496	24,358
State and Political Subdivisions [Member]
Held-to-maturity [Abstract]
Amortized cost	858	866
Gross unrealized gains	0	1
Gross unrealized losses	0	0
Fair value	$ 858	$ 867