Financial Instruments (Narrative) (Details) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended	9 Months Ended		12 Months Ended
	Aug. 31, 2016 $ / shares shares	Sep. 30, 2021 USD ($) item $ / shares shares	Sep. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Sep. 30, 2021 USD ($) item $ / shares shares	Sep. 30, 2020 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2020 USD ($) shares
Financial Instruments [Line Items]
Convertible debt fair value		$ 348,300			$ 348,300
Equity securities fair value		$ 9,196			9,196			$ 10,564
Equity securities, unrealized loss					$ 1,368	$ 12,975
Realized gain on equity securities			$ 4,274			19,784
Common Stock, Shares, Issued \| shares		176,489,990			176,489,990			171,530,045
Warrants outstanding, shares \| shares		6,261,586			6,261,586			10,582,119
MeiraGTx Ltd. [Member]
Financial Instruments [Line Items]
Ownership percentage					1.60%
Equity securities fair value		$ 9,200			$ 9,200			$ 10,600
Equity securities, unrealized loss		1,600	3,300	$ 1,400		32,800
Realized gain on equity securities		0	4,200		0	15,500
Warrants [Member]
Financial Instruments [Line Items]
Fair value of liability		$ 3,408			$ 3,408			$ 1,082
2015 Credit Agreement, Warrants [Member]
Financial Instruments [Line Items]
Warrants to purchase							$ 6,300
Common units converted to warrants \| shares	617,651
Strike price \| $ / shares	$ 10.20	$ 4.50			$ 4.50
Warrants outstanding, shares \| shares		88,238			88,238
Expected term		10 months 24 days			10 months 24 days
Change in fair value of warrant		$ 2,700	$ (600)		$ 2,300	$ (500)
Warrants exercised \| shares		0			0
2015 Credit Agreement, Warrants [Member] \| Expected Dividend Yield [Member]
Financial Instruments [Line Items]
Warrants and Rights Outstanding, Measurement Input \| item		0			0
2015 Credit Agreement, Warrants [Member] \| Expected Volatility [Member]
Financial Instruments [Line Items]
Warrants and Rights Outstanding, Measurement Input \| item		0.850			0.850
2015 Credit Agreement, Warrants [Member] \| Risk Free Interest Rate [Member]
Financial Instruments [Line Items]
Warrants and Rights Outstanding, Measurement Input \| item		0.001			0.001
2015 Credit Agreement, Fifth Amendment [Member]
Financial Instruments [Line Items]
Strike price \| $ / shares		$ 3.30			$ 3.30
Warrants outstanding, shares \| shares		529,413			529,413

Kadmon Holdings, Inc. 10-Q