Trading Securities (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	$ 150,887,000	$ 214,102,000	$ 204,242,000
Trading Securities, Net Unrealized Gain (Loss)	(86,000)	151,000	684,000
U.S. Government agency debentures [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	74,632,000	16,545,000	3,100,000
Trading Securities, Net Unrealized Gain (Loss)	(598,000)	(57,000)	1,000
U.S. agency residential mortgage-backed securities [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	26,129,000	86,361,000	119,835,000
Trading Securities, Net Unrealized Gain (Loss)	456,000	447,000	566,000
Municipal and other tax-exempt securities [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	37,057,000	90,326,000	58,150,000
Trading Securities, Net Unrealized Gain (Loss)	81,000	(226,000)	118,000
Trading Securities, Pledged as Collateral	0	13,000,000	0
Other trading securities [Member]
Schedule of Trading Securities [Line Items]
Trading Securities, Fair Value	13,069,000	20,870,000	23,157,000
Trading Securities, Net Unrealized Gain (Loss)	$ (25,000)	$ (13,000)	$ (1,000)