Securities Fair Value Option Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
Schedule of Fair Value Option Securities [Line Items]
Fair Value Option Securities, Fair Value	$ 222,409	$ 444,217	$ 427,760
Fair Value Option Securities, Net Unrealized Gain or Loss	(2,397)	(2,060)	2,067
U.S. Treasury
Schedule of Fair Value Option Securities [Line Items]
Fair Value Option Securities, Fair Value	222,409	0	0
Fair Value Option Securities, Net Unrealized Gain or Loss	(2,397)	0	0
U.S. government agency residential mortgage-backed securities
Schedule of Fair Value Option Securities [Line Items]
Fair Value Option Securities, Fair Value	0	444,217	427,760
Fair Value Option Securities, Net Unrealized Gain or Loss	$ 0	$ (2,060)	$ 2,067