Share-Based Compensation - Stock Option Activity (Details)	9 Months Ended
	Sep. 30, 2019 $ / shares shares	Dec. 31, 2018 $ / shares shares
Options
Outstanding at beginning of period (in shares) | shares	13,884,470
Granted (in shares) | shares	42,253
Exercised (in shares) | shares	(2,393,014)
Canceled/forfeited (in shares) | shares	(445,886)
Expired (in shares) | shares	(3,920)
Outstanding at end of period (in shares) | shares	11,083,903
Outstanding, vested and exercisable at end of period (in shares) | shares	8,083,208	7,712,264
Weighted- Average Exercise Price
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 5.36
Granted (in dollars per share) | $ / shares	10.31
Exercised (in dollars per share) | $ / shares	5.04
Canceled/forfeited (in dollars per share) | $ / shares	2.53
Expired (in dollars per share) | $ / shares	12.98
Outstanding at end of period (in dollars per share) | $ / shares	5.56
Outstanding, vested and exercisable at end of period (in dollars per share) | $ / shares	$ 6.59	$ 7.37