Securities, Amortized Cost and Fair Value of Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Available-for-sale, amortized cost [Abstract]
Due in one year or less	$ 46,660
Due after one through five years	133,244
Due after five through ten years	76,825
Due after ten years	116,847
Amortized cost	582,983	$ 590,199
Available-for-sale, fair value [Abstract]
Due in one year or less	46,471
Due after one through five years	131,223
Due after five through ten years	75,192
Due after ten years	113,905
Total securities	569,208	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	208,900
Available-for-sale, fair value [Abstract]
Without single maturity date	201,911
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]
Available-for-sale, amortized cost [Abstract]
Without single maturity date	507
Available-for-sale, fair value [Abstract]
Without single maturity date	506
Held-to-maturity, amortized cost [Abstract]
Without single maturity date	0
Held-to-maturity, fair value [Abstract]
Without single maturity date	$ 0