Share Incentive Plans - Information Regarding Options Outstanding and Exercisable (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Share Based Compensation [Abstract]
Options Outstanding, Options | shares	7,112,235
Options Exercisable, Options | shares	5,328,020
Options, Vested and expected to vest | shares	7,096,243
Options Outstanding, Weighted Average Remaining Contractual Life in Years	5 years 6 months 29 days
Options Exercisable, Weighted Average Remaining Contractual Life in Years	4 years 6 months 7 days
Options Vested and expected to vest, Weighted Average Remaining Contractual Life in Years	5 years 6 months 25 days
Options Outstanding, Weighted Average Exercise Price | $ / shares	$ 52.35
Options Exercisable, Weighted Average Exercise Price | $ / shares	49.57
Vested and expected to vest, Weighted Average Exercise Price | $ / shares	$ 52.33
Options Outstanding, Aggregate Intrinsic Value | $	$ 97,633
Options Exercisable, Aggregate Intrinsic Value | $	88,031
Vested and expected to vest, Aggregate Intrinsic Value | $	$ 97,543