Stock-Based Compensation Restricted Stock (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Allocated Share-based Compensation Expense	$ 2.5	$ 3.3	$ 7.0	$ 6.4
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Restricted stock, beginning of period			486,533
Restricted stock, granted			120,123
Restricted stock, released			(154,903)
Restricted stock, forfeited			(36,976)
Restricted stock, end of period	414,777		414,777
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Weighted Average Grant Date Fair Value, Beginning balance			$ 31.25
Weighted Average Grant Date Fair Value, Granted			$ 51.85
Weighted Average Grant Date Fair Value, Released			$ 11.03
Weighted Average Grant Date Fair Value, Forfeited			$ 40.90
Weighted Average Grant Date Fair Value, Ending balance	$ 43.72		$ 43.72
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Restricted stock, beginning of period			18,000
Restricted stock, granted			19,152
Restricted stock, released			(3,910)
Restricted stock, forfeited			0
Restricted stock, end of period	33,242		33,242
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Weighted Average Grant Date Fair Value, Beginning balance			$ 29.32
Weighted Average Grant Date Fair Value, Granted			$ 52.23
Weighted Average Grant Date Fair Value, Released			$ 40.58
Weighted Average Grant Date Fair Value, Forfeited			$ 0.00
Weighted Average Grant Date Fair Value, Ending balance	$ 41.19		$ 41.19
Board of Directors [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Deferred Compensation Arrangement with Individual, Shares Issued			44,957
Deferred Compensation Arrangement with Individual, Shares Outstanding	37,184		37,184
Allocated Share-based Compensation Expense			$ 0.2	$ 0.8