Employee Stock Plans - Stock Option Activity Table (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Shares outstanding	1,744,345	1,813,198
Shares outstanding, weighted-average exercise price	$ 50.72	$ 46.29
Shares granted	506,976
Shares granted, weighted-average exercise price	$ 56.96
Shares exercised	(476,489)
Shares exercised, weighted-average exercise price	$ 39.81
Shares forfeited	(99,340)
Shares forfeited, weighted-average exercise price	$ 54.01
Shares exercisable	751,360
Shares exercisable, weighted-average exercise price	$ 42.43
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Remaining Contractual Term	61 months
Shares outstanding, weighted-average remaining contractual life	83 months
Shares outstanding, aggregate intrinsic value	$ 35,895
Shares exercisable, aggregate intrinsic value	$ 21,689