Net Income (Loss) Per Common Share (Anti-Dilutive Common Share Equivalents) (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded (in shares)	8,184,291	3,020,562	6,628,241	5,169,484
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded (in shares)	4,498,581	2,840,298	4,151,551	4,586,476
Warrants to purchase common stock | Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded (in shares)	0	22,000	0	22,000
RSUs and PRSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded (in shares)	3,099,262	124,582	1,890,242	527,326
Employee stock purchase plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded (in shares)	586,448	33,682	586,448	33,682