Equity - Narrative (Details)				3 Months Ended		12 Months Ended
	Dec. 18, 2019 $ / shares shares	Aug. 10, 2017 USD ($)	Jun. 27, 2017 $ / shares shares	Mar. 31, 2020 USD ($) vote $ / shares shares	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) $ / shares shares
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)				87,019,172
Class of warrant or right, outstanding (in shares)				31,426,248,000
Warrant liabilities | $				$ 42,395,000		$ 41,549,000
Shares issued, value | $				$ 0	$ 30,942,000
Exercise price (in dollars per share) | $ / shares				$ 1,120
Common stock, par value (in dollars per share) | $ / shares				$ 0.0001		$ 0.0001
Common stock, shares authorized (in shares)				200,000,000		200,000,000
Number of votes per share that common stockholders are entitled to | vote				1
Dividends declared or paid on common stock | $				$ 0
December 2019 Financing
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	37,634,883
Share price (in dollars per share) | $ / shares	$ 1.46			$ 0.125
Class of warrant or right, outstanding (in shares)				22,988,501
Warrant Issued | $				$ 40,700,000
Warrant liabilities | $				41,500,000
Warrant, increase (decrease) in equity, amount | $				(800,000)
Sale common stock | $				65,600,000
Issuance costs | $				$ 4,400,000
Exercise price (in dollars per share) | $ / shares				$ 1.46
At-The-Market Offering
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)				598,977		615,453
Share price (in dollars per share) | $ / shares				$ 2.11		$ 1.84
Sale common stock | $				$ 50,000,000
Shares issued, value | $				$ 1,141,000	$ 0	$ 1,000,000.0
Public securities offering, amount authorized | $		$ 200,000,000.0
2017 PIPE
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)			2,750,000
Share price (in dollars per share) | $ / shares			$ 16.00
Common stock, par value (in dollars per share) | $ / shares				$ 0.0001
Common stock, shares authorized (in shares)				200,000,000
Springer Purchase Agreement
Subsidiary, Sale of Stock [Line Items]
Share price (in dollars per share) | $ / shares			$ 17.71
Springer Purchase Agreement | Common stock
Subsidiary, Sale of Stock [Line Items]
Stock issued (in shares)			338,791
Warrant
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)			79,130
Exercise price (in dollars per share) | $ / shares			$ 17.71
Warrants and rights outstanding, term			5 years
Share price (in dollars per share) | $ / shares			$ 0.125
Warrant
Subsidiary, Sale of Stock [Line Items]
Class of warrant or right, outstanding (in shares)				8,437,747,000
Warrant | December 2019 Financing
Subsidiary, Sale of Stock [Line Items]
Aggregate shares of common stock at a purchase price (in shares)				8,342,128