Investment Securities, Contract Maturity (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Amortized Cost [Abstract]
Within one year	$ 67,480
After one year through five years	20,887
After five years through ten years	0
After ten years	0
Amortized cost, before single maturity date	88,367
Investment securities not due at a single maturity date, mortgage-backed securities	270,820
Amortized cost, Total	359,187
Fair/Book Value [Abstract]
Within one year	67,483
After one year through five years	21,100
After five years through ten years	0
After ten years	0
Fair/Book Value, before single maturity date	88,583
Investment securities not due at a single maturity date, mortgage-backed securities	276,601
Fair/Book Value, Total	365,184	366,542	399,743
Book Value [Abstract]
Within one year	2,739
After one year through five years	16,132
After five years through ten years	10,313
After ten years	34,279
Book value, before single maturity date	63,463
Investment securities not due at a single maturity date, mortgage-backed securities	0
Book Value	63,463	63,863	65,655
Fair Value [Abstract]
Within one year	2,740
After one year through five years	16,294
After five years through ten years	10,423
After ten years	34,761
Fair value, before single maturity date	64,218
Investment securities not due at a single maturity date, Mortgage-backed securities	0
Fair Value	$ 64,218	$ 64,635	$ 66,109