Shareholders' Equity - Treasury Stock (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended			20 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	May 02, 2012
Equity [Abstract]
Number of shares authorized to be repurchased					5,000,000
Stock repurchased during period, shares				1,800,000
Purchase of treasury stock	$ (2.5)	$ (6.5)	$ (9.7)	$ (9.0)
Remaining number of shares authorized to be repurchased	3,200,000			3,200,000
Average price per share of treasury stock acquired and held	$ 24.03
Movement in Treasury Stock [Roll Forward]
Treasury Shares, Beginning Balance (in shares)	1,563,321	4,663,923	4,212,285
Purchases (in shares)	616,581	1,236,161	1,099,219
Exercise of stock options (in shares)	0	0	(45,429)
Restricted stock grants and other (in shares)	(622,241)	(499,851)	(365,712)
401(k) matching contribution (in shares)	(435,735)	(517,588)	(236,440)
Shares issued for acquisition		(3,319,324)
Treasury Shares, Ending Balance (in shares)	1,121,926	1,563,321	4,663,923	1,121,926