Net Income (Loss) Per Share Attributable to Common Stockholders - Antidilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Securities excluded from the calculation of weighted average common shares outstanding
Total anti-dilutive securities outstanding (shares)	7,802,172	8,697,680	8,829,434
Stock option awards
Securities excluded from the calculation of weighted average common shares outstanding
Total anti-dilutive securities outstanding (shares)	5,327,756	6,348,251	6,311,059
Restricted stock unit awards
Securities excluded from the calculation of weighted average common shares outstanding
Total anti-dilutive securities outstanding (shares)	2,474,416	2,349,429	2,518,375