Stock-Based Compensation - Stock Option Activity (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares shares
Number of Option Shares
Options outstanding (in shares) | shares	5,869,211
Granted (in shares) | shares	2,436,811
Exercised (in shares) | shares	(230,644)
Forfeited (in shares) | shares	(257,942)
Options outstanding (in shares) | shares	7,817,436
Options outstanding, weighted average remaining contractual term	4 years 10 months 2 days
Options outstanding, aggregate intrinsic value | $	$ 75.1
Weighted-Average Exercise Price
Options outstanding (in dollars per share) | $ / shares	$ 15.14
Granted (in dollars per share) | $ / shares	19.24
Exercised (in dollars per share) | $ / shares	14.32
Forfeited (in dollars per share) | $ / shares	19.44
Options outstanding (in dollars per share) | $ / shares	$ 16.30
Options Exercisable
Options exercisable (in shares) | shares	4,071,052
Options exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 13.62
Options exercisable, weighted average remaining contractual term	2 years 5 months 26 days
Options exercisable, aggregate intrinsic value | $	$ 49.2