Trading Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	$ 181,131	$ 188,700	$ 169,712
Trading Securities, Net Unrealized Gain (Loss)	606	187	(1,855)
U.S. Government agency debentures [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	42,431	85,092	41,004
Trading Securities, Net Unrealized Gain (Loss)	(38)	(62)	(5)
U.S. agency residential mortgage-backed securities [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	30,973	31,199	33,226
Trading Securities, Net Unrealized Gain (Loss)	195	269	(2,002)
Municipal and other tax-exempt securities [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	84,261	38,951	76,884
Trading Securities, Net Unrealized Gain (Loss)	421	18	90
Other trading securities [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	23,466	33,458	18,598
Trading Securities, Net Unrealized Gain (Loss)	$ 28	$ (38)	$ 62