Stock Incentive Plans (Details 2) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Options, additional information
Total unrecognized stock-based compensation expense	$ 5.8
Weighted-average period over which this expense will be recognized	9 months 18 days
Employee nonstatutory stock options
Stock Incentive Plans
Number Outstanding (in shares)	2,320,687
Number Exercisable (in shares)	1,349,616
Weighted-average remaining contractual term of exercisable options (in years)	2 years 4 months 28 days
Options Granted
Number of nonstatutory stock options granted (in shares)	550,805	474,518	421,385
Stock or Unit Option Plan Expense	$ 9.9	$ 12.0	$ 12.7
Assumptions used for estimating the fair value of stock options
Weighted average expected volatility (as a percent)	24.50%	28.60%	33.30%
Risk-free rate	1.30%	1.25%	0.61%
Dividend yield	0.00%	0.00%	0.00%
Volatility rate, minimum	23.00%	28.20%	32.30%
Volatility rate, maximum	27.20%	28.70%	34.30%
Options, additional information
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 19.28	$ 20.12	$ 19.26
Stock or Unit Option Plan Expense	$ 9.9	$ 12.0	$ 12.7
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
Employee nonstatutory stock options | Exercise Price Range Two [Member]
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
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
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)	985,206
Number Exercisable (in shares)	985,206
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	11 months 1 day
Weighted-Average Exercise Price (in dollars per share)	$ 45.30
Employee nonstatutory stock options | Exercise Price Range Six [Member]
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)	16,499
Number Exercisable (in shares)	16,499
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	1 year 11 months 8 days
Weighted-Average Exercise Price (in dollars per share)	$ 66.70
Employee nonstatutory stock options | Exercise Price Range Eight [Member]
Stock Incentive Plans
Exercise price, low end of range (in dollars per share)	70
Exercise price, high end of range (in dollars per share)	$ 80
Number Outstanding (in shares)	332,279
Number Exercisable (in shares)	209,074
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	2 years 3 months 26 days
Weighted-Average Exercise Price (in dollars per share)	$ 76.66
Employee nonstatutory stock options | Exercise Price Range Nine [Member]
Stock Incentive Plans
Exercise price, low end of range (in dollars per share)	80
Exercise price, high end of range (in dollars per share)	$ 90
Number Outstanding (in shares)	1,631
Number Exercisable (in shares)	890
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	2 years 5 months 27 days
Weighted-Average Exercise Price (in dollars per share)	$ 84.74
Employee nonstatutory stock options | Exercise Price Range Ten [Member]
Stock Incentive Plans
Exercise price, low end of range (in dollars per share)	90
Exercise price, high end of range (in dollars per share)	$ 100
Number Outstanding (in shares)	957,572
Number Exercisable (in shares)	131,072
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	3 years 11 months 19 days
Weighted-Average Exercise Price (in dollars per share)	$ 92.94
Employee nonstatutory stock options | Exercise Price Range Eleven [Member]
Stock Incentive Plans
Exercise price, low end of range (in dollars per share)	100
Exercise price, high end of range (in dollars per share)	$ 110
Number Outstanding (in shares)	27,500
Number Exercisable (in shares)	6,875
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term	3 years 1 month 27 days
Weighted-Average Exercise Price (in dollars per share)	$ 100.29
Restricted Stock Units (RSUs) [Member]
Options Granted
Stock or Unit Option Plan Expense	$ 5.8	$ 0.0	$ 0.0
Options, additional information
Performance Based Units Granted	123,846	110,993	111,770
Performance Based Units, Forfeitures	10,641	8,570	5,513
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 96.12	$ 92.92	$ 76.66
Percent of Units Expected to Settle in Common Stock	53.00%	53.00%	54.00%
Percent of Units Expected to Settle in Cash	47.00%	47.00%	46.00%
Stock or Unit Option Plan Expense	$ 5.8	$ 0.0	$ 0.0
Stock or Unit Option Plan Expense, Unrecognized	$ 11.1
Weighted-Average Remaining Contractual Term (in years)	1 year 8 months 12 days
Restricted Stock Units (RSUs) [Member] | Minimum
Options, additional information
Performance Based Compensation Payout Target	0.00%
Restricted Stock Units (RSUs) [Member] | Maximum
Options, additional information
Performance Based Compensation Payout Target	200.00%
Performance Based Units [Member]
Options, additional information
Performance Based Units Granted	1,864