Securities, Amortized Cost and Fair Value of Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Available-for-sale, amortized cost [Abstract]
Due in one year or less	$ 29,546
Due after one through five years	93,079
Due after five through ten years	80,646
Due after ten years	98,109
Amortized cost	601,544	$ 602,114
Available for sale, fair value [Abstract]
Due in one year or less	29,499
Due after one through five years	93,111
Due after five through ten years	80,248
Due after ten years	98,348
Fair value	599,299	593,746
Held-to-maturity, amortized cost [Abstract]
Due in one year or less	619
Due after one through five years	0
Due after five through ten years	0
Due after ten years	0
Amortized cost	619	649
Held-to-maturity, fair value [Abstract]
Due in one year or less	619
Due after one through five years	0
Due after five through ten years	0
Due after ten years	0
Fair value	619	649
U.S. Government Sponsored Agency Mortgage-backed Securities [Member]
Available-for-sale, amortized cost [Abstract]
Without single maturity date	299,658
Amortized cost	299,658	255,969
Available for sale, fair value [Abstract]
Without single maturity date	297,591
Fair value	297,591	250,819
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	506
Amortized cost	506	507
Available for sale, fair value [Abstract]
Without single maturity date	502
Fair value	502	$ 501
Held-to-maturity, amortized cost [Abstract]
Without single maturity date	0
Held-to-maturity, fair value [Abstract]
Without single maturity date	$ 0