Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) (Unaudited) (USD $)	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Consolidated Statements of Changes In Shareholders' Equity [Abstract]
Common stock, par value	$ 0.001	$ 0.001
Options exercised, shares	297,592	136,290
Conversion of common stock units, shares	15,084	15,715
Conversion of restricted stock units, shares	91,327	170,876
Cash dividends, per share	$ 0.39	$ 0.33
Treasury stock, beginning balance, shares	22,028,030	21,813,196
Treasury stock, acquisition of shares	801,086	60,126
Treasury stock, ending balance, shares	22,829,116	21,873,322