License Agreements - Agenus (Details) $ / shares in Units, $ in Thousands, shares in Millions	1 Months Ended	3 Months Ended		12 Months Ended				87 Months Ended
	Jan. 31, 2015 item	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($) shares		Dec. 31, 2020 USD ($) shares	Dec. 31, 2017 USD ($) $ / shares shares	Mar. 31, 2022 USD ($)
License agreements
Long term investments		$ 174,681		$ 221,266	[1]			$ 174,681
Unrealized gain (loss) on long term investments		(46,585)	$ (27,709)
Research and development expense		353,373	306,896
Agenus
License agreements
Long term investments		$ 29,700		$ 38,900				$ 29,700
Shares divested (in shares) | shares				2.0		3.7
Gross proceeds from sale of stock				$ 10,500		$ 17,200
Ownership percentage (as a percent)		5.00%						5.00%
Unrealized gain (loss) on long term investments		$ (9,200)	$ (5,900)
Stock purchase agreement | Agenus
License agreements
Purchase of common stock under Stock Purchase Agreement (in shares ) | shares							10.0
Purchase price of common stock							$ 60,000
Per share price | $ / shares							$ 6.00
Agenus
License agreements
Number of program targets | item	4
Royalty payments on future global net sales (as a percent)		15.00%
Agenus | Development, Regulatory and Commercialization Milestones
License agreements
Milestone payment made under license agreement								$ 30,000
Additional milestone payments under the license agreement		$ 500,000						$ 500,000
Agenus | Development, Regulatory and Commercialization Milestones | Minimum
License agreements
Royalty payments on future global net sales (as a percent)		6.00%
Agenus | Development, Regulatory and Commercialization Milestones | Maximum
License agreements
Royalty payments on future global net sales (as a percent)		12.00%

[1] The condensed consolidated balance sheet at December 31, 2021 has been derived from the audited consolidated financial statements at that date.