Trading Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	$ 211,622	$ 122,404	$ 158,209
Trading Securities, Net Unrealized Gain (Loss)	786	140	159
U.S. government agency debentures [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	18,909	61,295	40,212
Trading Securities, Net Unrealized Gain (Loss)	(8)	(71)	(28)
U.S. government agency residential mortgage-backed securities [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	122,306	10,989	23,090
Trading Securities, Net Unrealized Gain (Loss)	363	17	181
Municipal and other tax-exempt securities [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	52,721	31,901	62,801
Trading Securities, Net Unrealized Gain (Loss)	262	210	(41)
Other trading securities [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	17,686	18,219	32,106
Trading Securities, Net Unrealized Gain (Loss)	$ 169	$ (16)	$ 47