Trading Securities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	$ 169,712	$ 91,616	$ 150,887
Trading Securities, Net Unrealized Gain (Loss)	(1,855)	11	(86)
U.S. Government agency debentures [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	41,004	34,120	74,632
Trading Securities, Net Unrealized Gain (Loss)	(5)	77	(598)
U.S. agency residential mortgage-backed securities [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	33,226	21,011	26,129
Trading Securities, Net Unrealized Gain (Loss)	(2,002)	123	456
Municipal and other tax-exempt securities [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	76,884	27,350	37,057
Trading Securities, Net Unrealized Gain (Loss)	90	(182)	81
Other trading securities [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	18,598	9,135	13,069
Trading Securities, Net Unrealized Gain (Loss)	$ 62	$ (7)	$ (25)