Mandatorily Redeemable Preferred Shares, net - Narrative (Details) $ / shares in Units, $ in Thousands		1 Months Ended		3 Months Ended			9 Months Ended
	Aug. 07, 2020 $ / shares shares	Aug. 31, 2020 $ / shares shares	Apr. 30, 2019 USD ($) closing $ / shares shares	Sep. 30, 2020 USD ($) shares	Jun. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) shares	Sep. 30, 2019 USD ($)	Mar. 31, 2021	Dec. 31, 2019 shares
Mandatorily Redeemable Preferred Shares
Fee to be recognized for nonissuance of shares				$ 3,000
Interest expense				$ 7,310		$ 4,378	$ 19,864	$ 8,333
Gain on settlement of derivative liability					$ 650
Series A preferred shares
Mandatorily Redeemable Preferred Shares
Number of shares sold in transaction (in shares) | shares			2,495
Issuance price per share (in dollars per share) | $ / shares			$ 50,100
Gross proceeds from transaction			$ 125,000
Payment for priority review voucher			$ 105,000
Number of additional closings per share agreement, maximum | closing			3
Aggregate value of additional closings available per share agreement			$ 75,000
Maximum fee per share agreement for nonissuance of shares			$ 3,000
Redemption relative to original purchase price upon optional redemption			2
Annual interest rate upon default of redemption (percent)			18.00%
Effective interest rate (percent)				18.00%			18.00%
Partial settlement of Series A preferred shares derivative liability							$ 42,821
Mandatorily redeemable shares issued (in shares) | shares				2,495			2,495			2,495
Mandatorily redeemable shares outstanding (in shares) | shares				2,495			2,495			2,495
Series A preferred shares | Forecast
Mandatorily Redeemable Preferred Shares
Redemption relative to original purchase price upon required redemption									2
Series A preferred shares | Change of control
Mandatorily Redeemable Preferred Shares
Redemption relative to original purchase price upon required redemption			2
Series B preferred shares
Mandatorily Redeemable Preferred Shares
Number of shares sold in transaction (in shares) | shares	3,992	3,992
Issuance price per share (in dollars per share) | $ / shares	$ 50,100	$ 50,100
Mandatorily redeemable shares issued (in shares) | shares				0			0			0
Mandatorily redeemable shares outstanding (in shares) | shares				0			0			0