Securities, Amortized Cost and Fair Value of Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Available-for-sale debt securities [Abstract]
Amortized cost	$ 614,333	$ 565,199
Gross unrealized gains	1,466	2,544
Gross unrealized losses	(10,909)	(6,340)
Fair value	604,890	561,403
Available-for-sale equity securities [Abstract]
Amortized cost		25,000
Available-for-sale [Abstract]
Amortized cost	614,333	590,199
Gross unrealized gains	1,466	2,620
Gross unrealized losses	(10,909)	(7,058)
Securities available-for-sale at fair value (amortized cost of $590,199 and $608,939, respectively)	604,890	585,761
Held-to-maturity [Abstract]
Amortized cost	659	659
Gross unrealized gains	1	1
Gross unrealized losses	0	0
Fair value	660	660
U.S. Treasury and Government Agencies [Member]
Available-for-sale debt securities [Abstract]
Amortized cost	252,203	211,574
Gross unrealized gains	200	170
Gross unrealized losses	(2,358)	(1,172)
Fair value	250,045	210,572
State and Political Subdivisions [Member]
Available-for-sale debt securities [Abstract]
Amortized cost	134,764	144,159
Gross unrealized gains	985	2,017
Gross unrealized losses	(2,754)	(1,161)
Fair value	132,995	145,015
U.S. Government Sponsored Agency Mortgage-backed Securities [Member]
Available-for-sale debt securities [Abstract]
Amortized cost	226,859	208,959
Gross unrealized gains	281	357
Gross unrealized losses	(5,797)	(4,007)
Fair value	221,343	205,309
Other Debt Securities [Member]
Available-for-sale debt securities [Abstract]
Amortized cost	507	507
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair value	507	507
CRA Investments Funds [Member]
Available-for-sale equity securities [Abstract]
Amortized cost	0	25,000
Gross unrealized gains	0	76
Gross unrealized losses	0	(718)
Fair value	0	24,358
State and Political Subdivisions [Member]
Held-to-maturity [Abstract]
Amortized cost	659	659
Gross unrealized gains	1	1
Gross unrealized losses	0	0
Fair value	$ 660	$ 660