Basic and Diluted Net Loss per Common Share (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net loss attributable to common stockholders	$ (88,948)	$ (120,299)
Denominator:
Weighted-average common shares outstanding - basic and diluted (in shares)	256,968,248	213,519,287
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	29,664,000	31,912,000
Options to purchase common stock
Denominator:
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	19,086,000	18,331,000
Convertible notes
Denominator:
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	462,000	5,017,000
Outstanding warrants, convertible to common stock
Denominator:
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	2,554,000	2,554,000
Unvested restricted stock units
Denominator:
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	7,562,000	6,010,000