Stock-Based Compensation - Stock Options (Details) - Outstanding stock options $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2016 USD ($) $ / shares shares
Shares
Outstanding at the beginning of the period (in shares) | shares	5,878,352
Granted (in shares) | shares	1,509,986
Exercised (in shares) | shares	(154,269)
Cancelled (in shares) | shares	(154,335)
Outstanding at the end of the period (in shares) | shares	7,079,734
Vested at the end of the period (in shares) | shares	2,997,604
Weighted-average price per share
Outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 35.00
Granted (in dollars per share) | $ / shares	43.53
Exercised (in dollars per share) | $ / shares	30.80
Cancelled (in dollars per share) | $ / shares	49.81
Outstanding at the end of the period (in dollars per share) | $ / shares	36.59
Vested at the end of the period (in dollars per share) | $ / shares	$ 22.53
Additional disclosure
Unrecognized compensation costs | $	$ 103.6
Weighted average period over which unrecognized compensation costs are expected to be recognized	2 years 10 months 24 days