Share Based Award Stock Option Activity (Details) - Employee Stock Option [Member] $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, Outstanding, Number | shares	2,018,290
Granted | shares	8,825
Exercised | shares	(610,316)
Forfeited or expired | shares	(72)
Options, Outstanding, Number | shares	1,416,727
Exercisable | shares	1,133,734
Vested and Expected to Vest | shares	1,416,727
Options, Outstanding, Weighted Average Exercise Price | $ / shares	$ 58.90
Weighted Average Exercise Price | $ / shares	158.20
Options, Exercises in Period, Weighted Average Exercise Price | $ / shares	52.43
Options, Nonvested Options Forfeited, Weighted Average Grant Date Fair Value | $ / shares	58.79
Options, Outstanding, Weighted Average Exercise Price | $ / shares	62.30
Exercise Price Range, Exercisable Options, Weighted Average Exercise Price | $ / shares	60.13
Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price | $ / shares	$ 62.30
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	5 years 9 months
Options, Exercisable, Weighted Average Remaining Contractual Term	5 years 7 months
Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term	5 years 9 months
Options, Outstanding, Intrinsic Value | $	$ 217,749
Options, Exercisable, Intrinsic Value | $	176,721
Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value | $	$ 217,749