Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Consolidated Balance Sheets [Abstract]
Fair value of held-to-maturity investment securities	$ 46,409	$ 45,639
Accumulated amortization and fair value adjustments on other intangibles	$ 11,934	$ 11,646
Common stock, par value	$ 5	$ 5
Common stock, shares authorized	48,000,000	48,000,000
Common stock, shares issued	18,266,404	18,266,404
Common stock, shares outstanding	16,780,416	16,702,376
Treasury stock, shares	1,485,988	1,564,028