Trading Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	$ 337,628	$ 122,404
Trading Securities, Net Unrealized Gain (Loss)	738	140
U.S. government agency debentures [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	6,234	61,295
Trading Securities, Net Unrealized Gain (Loss)	(4)	(71)
U.S. government agency residential mortgage-backed securities [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	310,067	10,989
Trading Securities, Net Unrealized Gain (Loss)	635	17
Municipal and other tax-exempt securities [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	14,427	31,901
Trading Securities, Net Unrealized Gain (Loss)	50	210
Other trading securities [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	6,900	18,219
Trading Securities, Net Unrealized Gain (Loss)	$ 57	$ (16)