Investment Securities Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule of Investment Securities [Line Items]
Investment securities at fair value	$ 385,942	$ 374,790
Callable debt securities, fair value	68,100
Debt securities
Schedule of Investment Securities [Line Items]
Amortized Cost, Within One Year	16,217
Fair Value, Within One Year	16,262
Amortized Cost Basis, After One, But Within Five Years	112,615
Fair Value, After One, But Within Five Years	113,439
Amortized Cost, After Five, But Within Ten Years	117,552
Fair Value, after Five but Within Ten Years	118,680
Amortized Cost Basis, After Ten Years	134,132
Fair Value, After Ten Years	134,515
Amortized cost	380,516	365,578
Investment securities at fair value	$ 382,896	$ 362,147