Securities, Amortized Cost and Fair Value of Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Available-for-sale, amortized cost [Abstract]
Due in one year or less	$ 22,413
Due after one through five years	156,063
Due after five through ten years	66,433
Due after ten years	142,058
Amortized cost	614,333	$ 590,199
Available-for-sale, fair value [Abstract]
Due in one year or less	22,386
Due after one through five years	154,452
Due after five through ten years	65,690
Due after ten years	140,512
Total securities	604,890	585,761
Held-to-maturity, amortized cost [Abstract]
Due in one year or less	0
Due after one through five years	659
Due after five through ten years	0
Due after ten years	0
Amortized cost	659	659
Held-to-maturity, fair value [Abstract]
Due in one year or less	0
Due after one through five years	660
Due after five through ten years	0
Due after ten years	0
Total debt securities	660	$ 660
U.S. Government Sponsored Agency Mortgage-backed Securities [Member]
Available-for-sale, amortized cost [Abstract]
Without single maturity date	226,859
Available-for-sale, fair value [Abstract]
Without single maturity date	221,343
Other Debt Securities [Member]
Available-for-sale, amortized cost [Abstract]
Without single maturity date	507
Available-for-sale, fair value [Abstract]
Without single maturity date	507
U.S. Government Sponsored Agency Mortgage-backed Securities [Member]
Held-to-maturity, amortized cost [Abstract]
Without single maturity date	0
Held-to-maturity, fair value [Abstract]
Without single maturity date	0
Other Debt Securities [Member]
Held-to-maturity, amortized cost [Abstract]
Without single maturity date	0
Held-to-maturity, fair value [Abstract]
Without single maturity date	$ 0