Shareholders' Equity (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Shareholders' Equity [Abstract]
Date of dividend declared	Mar. 24, 2000
Right agreement expired year	March 2010
Cash dividends declared per share	$ 1.16	$ 1.04	$ 1.00
Dividends payable	$ 25.1	$ 21.7	$ 19.8
Dividend per share declared	$ 0.31	$ 0.27	$ 0.25
Dividend declaration date	2011-12
Dividend payable date	2012-01