Securities Fair Value Option Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Schedule of Fair Value Option Securities [Line Items]
Fair Value Option Securities, Fair Value	$ 427,760	$ 311,597	$ 175,761
U.S. agency residential mortgage-backed securities [Member]
Schedule of Fair Value Option Securities [Line Items]
Fair Value Option Securities, Fair Value	427,760	311,597	175,761
Fair Value Option Securities, Unrealized Gain or Loss	$ 2,067	$ 1,624	$ (2,061)