Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2010	Dec. 31, 2009
Consolidated Balance Sheets [Abstract]
Amortized cost of securities available-for-sale	$ 1,274,258	$ 1,241,381
Fair value of securities held-to-maturity	$ 686,114	$ 523,450
Preferred stock shares authorized	200,000	200,000
Preferred stock shares issued	100,000	100,000
Preferred stock per share liquidation preference	$ 1,000	$ 1,000
Common stock par value	$ 0	$ 0
Common stock shares authorized	20,000,000	20,000,000
Common stock shares issued	16,151,062	16,151,112
Treasury stock shares	752,128	1,268,332