Equity - Narrative (Details)							12 Months Ended
	Dec. 18, 2019 $ / shares shares	Aug. 19, 2019 USD ($) $ / shares shares	Jan. 29, 2019 shares	Jan. 25, 2019 USD ($) $ / shares shares	Aug. 10, 2017 USD ($)	Jun. 27, 2017 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) vote $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares) | shares							86,325,547
Class of warrant or right, outstanding (in shares) | shares							31,426,248,000	95,619,000	176,432,000
Warrant liabilities | $							$ 41,549,000	$ 0
Shares issued, value | $							$ 30,942,000	$ 0	$ 10,000,000
Exercise price (in dollars per share) | $ / shares							$ 1,120	$ 17,120	$ 17,320
Common stock, par value (in dollars per share) | $ / shares							$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares) | 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) | shares	37,634,883
Share price (in dollars per share) | $ / shares	$ 1.46						$ 0.125
Class of warrant or right, outstanding (in shares) | shares							22,988,501
Warrant Issued | $							$ 40,700,000
Warrant liabilities | $							41,500,000
Warrant, Down Round Feature, (Increase) Decrease in Equity, Amount | $							900,000
Sale common stock | $							65,600,000
Issuance costs | $							$ 4,400,000
Exercise price (in dollars per share) | $ / shares							$ 1.46
Private Placement
Subsidiary, Sale of Stock [Line Items]
Shares issued, value | $							$ 5,715,000	$ 0	$ 47,114,000
Private Placement | Director
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares) | shares		3,178,174
Share price (in dollars per share) | $ / shares		$ 1.81
Proceeds from issuance of common stock, net | $		$ 5,700,000
Public Stock Offering
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares) | shares				20,000,000
Share price (in dollars per share) | $ / shares				$ 1.50
Sale common stock | $				$ 30,900,000
Over-Allotment Option
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares) | shares			2,188,706
At-The-Market Offering
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares) | shares							615,453
Share price (in dollars per share) | $ / shares							$ 1.84
Sale common stock | $							$ 50,000,000
Shares issued, value | $							$ 1,006,000	$ 0	$ 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) | shares						2,750,000
Share price (in dollars per share) | $ / shares						$ 16.00
Shares issued, value | $						$ 47,100,000
Common stock, par value (in dollars per share) | $ / shares							$ 0.0001
Common stock, shares authorized (in shares) | 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) | shares						338,791
Warrant
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares) | 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) | shares							8,437,747,000	95,619,000	176,432,000
Warrant | December 2019 Financing
Subsidiary, Sale of Stock [Line Items]
Aggregate shares of common stock at a purchase price (in shares) | shares							8,342,128