Stock-Based Compensation - Stock Options (Details) - Outstanding stock options $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) $ / shares shares
Shares
Outstanding at the beginning of the period (in shares) | shares	5,878,352
Granted (in shares) | shares	1,298,421
Exercised (in shares) | shares	(29,689)
Cancelled (in shares) | shares	(79,531)
Outstanding at the end of the period (in shares) | shares	7,067,553
Vested at the end of the period (in shares) | shares	2,646,197
Vested and expected to vest at the end of the period (in shares) | shares	6,527,560
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	43.22
Exercised (in dollars per share) | $ / shares	24.56
Cancelled (in dollars per share) | $ / shares	49.95
Outstanding at the end of the period (in dollars per share) | $ / shares	36.39
Vested at the end of the period (in dollars per share) | $ / shares	18.39
Vested and expected to vest at the end of the period (in dollars per share) | $ / shares	$ 35.44
Additional disclosure
Unrecognized compensation costs | $	$ 97.4
Weighted average period over which unrecognized compensation costs are expected to be recognized	3 years 1 month 6 days