Stock Plans (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Summary of Stock Option and RSA Activity
Beginning Balance, Shares | shares	7,262
Stock Options Granted, shares | shares	282
Stock Options Exercised, shares | shares	(1,844)
Forfeited, shares | shares	(216)
Stock Options Expired, shares | shares	0
Ending Balance, Shares | shares	5,484
Beginning balance, weighted average exercise price | $ / shares	$ 58.92
Stock Options Granted, weighted average exercise price | $ / shares	98.47
Stock Options Exercised, weighted average exercise price | $ / shares	46.95
Stock Options Forfeitures, weighted average exercise price | $ / shares	65.36
Stock Options Expired, weighted average exercise price | $ / shares	0
Ending balance, weighted average exercise price | $ / shares	$ 64.73
Options vested and expected to vest, shares | shares	5,473
Options vested and expected to vest, Weighted Average Exercise Price | $ / shares	$ 64.73
Options exercisable, shares | shares	3,230
Options exercisable, Weighted Average Exercise Price | $ / shares	$ 57.04
Beginning balance, shares | shares	7,215
RSAs Granted, shares | shares	2,221
Vested, shares | shares	(2,407)
Forfeited, shares | shares	(463)
Ending balance, shares | shares	6,566
Beginning Balance, Weighted Average Grant Price | $ / shares	$ 70.29
Granted, Weighted Average Grant Price | $ / shares	98.2
RSAs Vested, Weighted Average Grant Price | $ / shares	77.41
RSAs Forfeited, Weighted Average Grant Price | $ / shares	78.8
Ending Balance, Weighted Average Grant Price | $ / shares	$ 76.52