Stock Incentive Plans (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock incentive plan
Minimum exercise price to fair market value on the date of grant (as a percent)	100.00%
Stock Option Activity Roll Forward, Number of Shares
Options exercised (in shares)	(728,408)	(793,359)	(1,464,294)
Minimum
Stock incentive plan
Stock incentive plan vesting period	1 year
Maximum
Stock incentive plan
Stock incentive plan vesting period	3 years
Employee nonstatutory stock options
Stock Option Activity Roll Forward, Number of Shares
Options outstanding at the beginning of the period (in shares)	2,523,790	2,885,055	4,024,484
Options exercised (in shares)	(728,408)	(793,359)	(1,464,294)
Options forfeited (in shares)	(25,000)	(42,424)	(95,139)
Options terminated (in shares)	(500)		(1,381)
Options granted (in shares)	550,805	474,518	421,385
Options outstanding at the end of the period (in shares)	2,320,687	2,523,790	2,885,055
Stock Option Activity Roll Forward, Average Exercise Price
Average exercise price at the beginning of the period (in dollars per share)	$ 55.77	$ 42.60	$ 32.33
Options exercised (in dollars per share)	36.85	29.53	23.46
Options forfeited (in dollars per share)	92.57	68.07	52.17
Options terminated (in dollars per share)	100.29		42.26
Options granted (in dollars per share)	$ 96.01	93.39	76.70
Average exercise price at the end of the period (in dollars per share)		55.77	42.60
Stock Option Activity, Additional Disclosures
Weighted-Average Grant Date Fair Value (in dollars per share)	$ 19.28	$ 20.12	$ 19.26
Stock Option Activity Roll Forward, Non-vested, Number of Shares
Non-vested stock options at the beginning of the period (in shares)	959,842
Granted (in shares)	550,805
Vested/exercised (in shares)	(511,146)
Forfeited (in shares)	(25,500)
Non-vested stock options outstanding at the end of the period (in shares)	974,001	959,842
Stock Option Activity Roll Forward, Non-vested, Weighted-Average Grant Date Fair Value
Weighted average grant date fair value of non vested stock options at the beginning of the period (in dollars per share)	$ 20.12
Granted (in dollars per share)	19.28
Vested/Exercised (in dollars per share)	18.83
Forfeited (in dollars per share)	$ 15.37
Weighted average grant date fair value of non vested Stock options at the end of the period (in dollars per share)		$ 20.12
Summary of intrinsic value
Intrinsic value for the options outstanding	$ 66.7
Intrinsic value for the options exercisable	59.9
Total intrinsic value of all options exercised	$ 46.1	$ 53.6	$ 83.2
Restricted Stock Units (RSUs) [Member]
Stock incentive plan
Stock Issued During Period, Shares, Restricted Stock Award, Forfeited	10,641	8,570	5,513
Stock Option Activity, Additional Disclosures
Weighted-Average Grant Date Fair Value (in dollars per share)	$ 96.12	$ 92.92	$ 76.66