Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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Amount, before allowance for credit loss, of right to consideration in exchange for good or service transferred to customer, when right is conditioned on something other than passage of time.

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The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

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Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

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Agreements - Debiopharm (Details) - USD ($)	1 Months Ended		3 Months Ended														6 Months Ended		12 Months Ended
Agreements - Debiopharm (Details) - USD ($)	Dec. 31, 2017	May 31, 2017	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2016
Collaborative Agreements disclosures
Revenue from contract with customer			$ 13,416,000	$ 10,928,000	$ 9,287,000	$ 19,815,000	$ 39,448,000	$ 8,480,000	$ 39,020,000	$ 28,499,000	$ 13,846,000	$ 7,660,000	$ 7,408,000	$ 19,714,000	$ 18,029,000	$ 14,851,000	$ 21,506,000	$ 32,880,000	$ 53,446,000	$ 115,447,000	$ 48,628,000	$ 60,002,000
License and milestone fees
Collaborative Agreements disclosures
Revenue from contract with customer			1,747,000	672,000	1,321,000	11,540,000	29,580,000	79,000	31,080,000	18,730,000	5,076,000	76,000	76,000	10,077,000	10,692,000	6,070,000	5,152,000	16,762,000	15,280,000	79,469,000	15,305,000	26,915,000
Research and development support
Collaborative Agreements disclosures
Revenue from contract with customer			218,000	$ 388,000	$ 388,000	$ 383,000	$ 452,000	$ 650,000	$ 902,000	$ 1,478,000	$ 1,427,000	$ 1,354,000	$ 1,335,000	$ 1,059,000	$ 848,000	$ 772,000	2,781,000	$ 1,620,000	1,377,000	3,482,000	$ 5,175,000	$ 4,014,000
Costs of services and materials																	$ 22,000
Debiopharm \| Phase 3 Clinical Trial
Collaborative Agreements disclosures
Potential milestone payment			$ 25,000,000																25,000,000
Debiopharm \| Transfer of ImmunoGen technologies
Collaborative Agreements disclosures
Revenue from contract with customer	$ 4,500,000
Potential milestone payment		$ 5,000,000
Debiopharm \| Upfront payment \| IMGN529 program
Collaborative Agreements disclosures
Revenue from contract with customer		$ 25,000,000
Debiopharm \| License and milestone fees \| IMGN529 program
Collaborative Agreements disclosures
Revenue from contract with customer																				$ 29,500,000
Debiopharm \| License and milestone fees \| Transfer of ImmunoGen technologies
Collaborative Agreements disclosures
Revenue from contract with customer																			500,000
Debiopharm \| Research and development support
Collaborative Agreements disclosures
Costs of services and materials																			$ 99,000