Consolidated Statements of Changes in Stockholders' Equity (Unaudited) (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Statement of Stockholders' Equity [Abstract]
Dividends declared per share	$ 1.00	$ 0.91	$ 0.84
Income tax on unrealized gain on securities available for sale	$ 1,468	$ (923)	$ 1,720
Income tax on reclassification adjustment	9	(7)	(10)
Income tax on other comprehensive income	711	(1,157)	1,841
Deferred tax on minimum pension liability adjustment	$ (766)	$ (227)	$ 131