Share-based Compensation - Schedule of Stock Options Activity (Details) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($) $ / shares shares
Stock Option Activity
Beginning balance (in shares) | shares	8,930
Granted (in shares) | shares	705
Cancelled (in shares) | shares	(401)
Exercised (in shares) | shares	(638)
Ending balance (in shares) | shares	8,596
Vested and expected to vest at the end of the period | shares	8,545
Vested and exercisable at the end of the period | shares	6,669
Weighted Average Exercise Price
Balance at the beginning of the period (in dollars per share) | $ / shares	$ 29.46
Granted (in dollars per share) | $ / shares	25.12
Cancelled (in dollars per share) | $ / shares	27.26
Exercised (in dollars per share) | $ / shares	21.18
Balance at the end of the period (in dollars per share) | $ / shares	29.82
Vested and expected to vest at the end of the period (in dollars per share) | $ / shares	29.85
Vested and exercisable at the end of the period (in dollars per share) | $ / shares	$ 30.51
Weighted Average Remaining Contractual Term
Balance at the end of the period	5 years 10 months 24 days
Vested and expected to vest at the end of the period	5 years 10 months 24 days
Vested and exercisable at the end of the period	5 years 1 month 6 days
Intrinsic Value
Balance at the end of the period | $	$ 19,315
Vested and expected to vest at the end of the period | $	19,096
Vested and exercisable at the end of the period | $	$ 13,284