Stock-Based Compensation Disclosure of Restricted Stock (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended				3 Months Ended			3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012 Restricted Stock [Member]	Dec. 31, 2011 Restricted Stock [Member]	Mar. 31, 2012 Restricted Stock Units (RSUs) [Member]	Dec. 31, 2011 Restricted Stock Units (RSUs) [Member]	Mar. 31, 2012 Board of Directors [Member]	Mar. 31, 2012 Board of Directors [Member] Restricted Stock Units (RSUs) [Member]	Mar. 31, 2011 Board of Directors [Member] Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Grant Date Fair Value			$ 42.80	$ 31.18	$ 41.13	$ 29.32
Weighted Average Grant Date Fair Value, Granted			$ 51.85		$ 52.23
Weighted Average Grant Date Fair Value, Released			$ 7.00
Weighted Average Grant Date Fair Value, Forfeited			$ 38.68
Deferred Compensation Arrangement with Individual, Shares Issued								44,957
Deferred Compensation Arrangement with Individual, Shares Outstanding							41,957
Allocated Share-based Compensation Expense	$ 4.5	$ 3.1						$ 0.3	$ 0.8
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Restricted stock, beginning of period			486,533		18,000
Restricted stock, granted			120,123		19,152
Restricted stock, released			(125,914)
Restricted stock, forfeited			(14,194)
Restricted stock, end of period			466,548		37,152