Net Income (Loss) Per Common Share (Anti-Dilutive Common Share Equivalents) (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded (in shares)	6,491,071	5,423,547	11,410,980
RSUs and PRSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded (in shares)	1,823,538	702,024	3,342,640
Employee stock purchase plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded (in shares)	452,382	173,527	127,487
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	22,000
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded (in shares)	4,215,151	4,525,996	7,918,853