Stockholders' Equity - Common Stock and Warrants (Details) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended		12 Months Ended
	Apr. 13, 2020 USD ($)	Mar. 31, 2019 $ / shares shares	Mar. 31, 2020 item $ / shares shares	Mar. 31, 2019 USD ($) $ / shares	Dec. 31, 2019 $ / shares shares	Dec. 31, 2017 shares
Stockholders' equity
Preferred stock, Shares authorized			5,000,000
Preferred stock, par value | $ / shares			$ 0.01
Net proceeds from shares of common stock sold | $				$ 23,498
Common Stock Shares, Outstanding			306,959,462		303,378,515
Common stock, par value (in dollars per share) | $ / shares			$ 0.01		$ 0.01
Number of votes per share | item			1
Common stock shares issued		10,000,000
Par value, common stock | $ / shares			$ 0.01		0.01
Share price (in dollars per share) | $ / shares		$ 2.35		$ 2.35
Series A Junior Participating Cumulative Preferred Stock
Stockholders' equity
Preferred stock, par value | $ / shares			$ 0.01		$ 0.01
Common Stock Shares, Outstanding			0		0
At Market Issuance Sales Agreement
Stockholders' equity
Authorized amount | $	$ 75,000
Warrant Issued With Amazon And Walmart Stores Inc Transaction Agreement In 2017
Stockholders' equity
Number of warrants exercised (in shares)			26,188,434		26,188,434
Maximum | Warrant Issued With Amazon And Walmart Stores Inc Transaction Agreement In 2017
Stockholders' equity
Class of Warrant or Right Issued						110,573,392