Investment Securities (Details 3) (USD $)	0 Months Ended
	Jul. 02, 2012	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Other investment securities
Amortized Cost		$ 7,805,000	$ 9,768,000	$ 18,292,000
Fair Value		7,805,000	9,768,000	18,292,000
Gain or loss on liquidation of Federal Reserve Bank stock	0
Amortized Cost
Due in one year or less		1,924,000
Due after one year through five years		345,000
Due after five years through ten years		8,927,000
Due after ten years		3,402,000
Total		14,598,000
Fair Value
Due in one year or less		1,955,000
Due after one year through five years		369,000
Due after five years through ten years		9,523,000
Due after ten years		3,708,000
Fair Value		15,555,000	16,553,000	17,664,000
Amortized Cost
Due in one year or less		3,946,000
Due after one year through five years		13,669,000
Due after five years through ten years		111,773,000
Due after ten years		370,588,000
Total		499,976,000	520,826,000	313,408,000
Fair Value
Due in one year or less		3,981,000
Due after one year through five years		14,011,000
Due after five years through ten years		114,088,000
Due after ten years		378,772,000
Fair Value		510,852,000	534,883,000	322,588,000
Federal Reserve Bank stock
Other investment securities
Amortized Cost				7,028,000
Fair Value				7,028,000
Federal Home Loan Bank stock
Other investment securities
Amortized Cost		6,163,000	8,126,000	9,932,000
Fair Value		6,163,000	8,126,000	9,932,000
Investment in unconsolidated subsidiaries
Other investment securities
Amortized Cost		1,642,000	1,642,000	1,332,000
Fair Value		$ 1,642,000	$ 1,642,000	$ 1,332,000