Consolidated Statement of Changes in Shareholders' Equity (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Issuance of shares for exercise of options, including tax effect	1,458	993	1,011
Purchase of common shares	12,645	1,660	3,013
Cash dividends declared per share	$ 0.60	$ 0.52	$ 0.47
Issuance of shares for debt conversion		1,040