Investment Securities, Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Amortized Cost [Abstract]
Within one year	$ 90,999
After one year through five years	68,672
After five years through ten years	0
After ten years	0
Amortized cost, excluding investment securities not due at a single maturity date	159,671
Investment securities not due at a single maturity date, mortgage-backed securities	195,860
Amortized cost	355,531
Fair/Book Value [Abstract]
Within one year	90,999
After one year through five years	69,321
After five years through ten years	0
After ten years	0
Fair/Book value, excluding investment securities not due at a single maturity date	160,320
Investment securities not due at a single maturity date, mortgage-backed securities	201,903
Fair/Book value	362,223	$ 369,137	$ 351,424
Book Value [Abstract]
Within one year	719
After one year through five years	11,275
After five years through ten years	12,426
After ten years	36,529
Book value, excluding investment securities not due at a single maturity date	60,949
Investment securities not due at a single maturity date, mortgage-backed securities	0
Book value	60,949	61,396	67,401
Fair Value [Abstract]
Within one year	719
After one year through five years	11,325
After five years through ten years	12,692
After ten years	38,107
Fair value, excluding investment securities not due at a single maturity date	62,843
Investment securities not due at a single maturity date, mortgage-backed securities	0
Fair value	$ 62,843	$ 62,388	$ 67,466