Stock Incentive Plans (Details 2) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Options, additional information
Total unrecognized stock-based compensation expense	$ 6.3
Weighted-average period over which this expense will be recognized	8 months 24 days
Employee nonstatutory stock options
Stock Incentive Plans
Number Outstanding (in shares)	2,885,055
Number Exercisable (in shares)	1,602,130
Weighted-average remaining contractual term of exercisable options (in years)	2 years 6 months 0 days
Options Granted
Number of nonstatutory stock options granted (in shares)	421,385	828,991	1,287,152
Assumptions used for estimating the fair value of stock options
Volatility rate, minimum	35.80%	46.50%	44.70%
Volatility rate, maximum	46.40%	50.70%	51.20%
Weighted average expected volatility (as a percent)	33.30%	40.60%	48.70%
Risk-free rate	0.61%	0.55%	1.43%
Dividend yield	0.00%	0.00%	0.00%
Options, additional information
Stock-based compensation expense recognized	12.7	14.7	14.0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 19.26	$ 16.67	$ 15.44
Employee nonstatutory stock options | Minimum
Assumptions used for estimating the fair value of stock options
Expected term	3 years	3 years	3 years
Employee nonstatutory stock options | Maximum
Assumptions used for estimating the fair value of stock options
Expected term	4 years	4 years	4 years
Employee nonstatutory stock options | Exercise Price Range One [Member]
Stock Incentive Plans
Exercise price, low end of range (in dollars per share)	$ 0
Exercise price, high end of range (in dollars per share)	$ 10
Number Outstanding (in shares)	253,551
Number Exercisable (in shares)	253,551
Weighted-Average Exercise Price (in dollars per share)	$ 9.79
Employee nonstatutory stock options | $10 - $20
Stock Incentive Plans
Exercise price, low end of range (in dollars per share)	$ 10
Exercise price, high end of range (in dollars per share)	$ 20
Employee nonstatutory stock options | Exercise Price Range Three [Member]
Stock Incentive Plans
Exercise price, low end of range (in dollars per share)	$ 20
Exercise price, high end of range (in dollars per share)	$ 30
Number Outstanding (in shares)	644,916
Number Exercisable (in shares)	644,916
Weighted-Average Exercise Price (in dollars per share)	$ 27.75
Employee nonstatutory stock options | Exercise Price Range Four [Member]
Stock Incentive Plans
Exercise price, low end of range (in dollars per share)	$ 30
Exercise price, high end of range (in dollars per share)	$ 40
Number Outstanding (in shares)	11,192
Number Exercisable (in shares)	5,794
Weighted-Average Exercise Price (in dollars per share)	$ 37.06
Employee nonstatutory stock options | Exercise Price Range Five [Member]
Stock Incentive Plans
Exercise price, low end of range (in dollars per share)	$ 40
Exercise price, high end of range (in dollars per share)	$ 50
Number Outstanding (in shares)	1,550,004
Number Exercisable (in shares)	689,602
Weighted-Average Exercise Price (in dollars per share)	$ 44.07
Employee nonstatutory stock options | $50 - $60
Stock Incentive Plans
Exercise price, low end of range (in dollars per share)	$ 50
Exercise price, high end of range (in dollars per share)	$ 60
Employee nonstatutory stock options | Exercise Price Range Seven [Member]
Stock Incentive Plans
Exercise price, low end of range (in dollars per share)	$ 60
Exercise price, high end of range (in dollars per share)	$ 70
Number Outstanding (in shares)	24,787
Number Exercisable (in shares)	8,267
Weighted-Average Exercise Price (in dollars per share)	$ 66.57
Employee nonstatutory stock options | Exercise Price Range Eight [Member] [Member]
Stock Incentive Plans
Number Outstanding (in shares)	398,380
Number Exercisable (in shares)
Weighted-Average Exercise Price (in dollars per share)
Employee nonstatutory stock options | Exercise Price Range Nine [Member]
Stock Incentive Plans
Number Outstanding (in shares)	2,225
Number Exercisable (in shares)
Weighted-Average Exercise Price (in dollars per share)
Performance Based Units [Member]
Stock Incentive Plans
Weighted-Average Remaining Contractual Term (in years)	2 years
Options, additional information
Stock-based compensation expense recognized	1.7
Stock or Unit Option Plan Expense, Unrecognized	$ 5.3
Performance Based Units Granted	111,770
Performance Based Units, Forfeitures	5,513
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 76.66
Percent of Units Expected to Settle in Common Stock	54.00%
Percent of Units Expected to Settle in Cash	46.00%
Performance Based Units [Member] | Minimum
Options, additional information
Performance Based Compensation Payout Target	0.00%
Performance Based Units [Member] | Maximum
Options, additional information
Performance Based Compensation Payout Target	200.00%