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Fair Value Measurements - Additional information (Details) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Nov. 29, 2016
Fair value measurements |  |  |
Gain on Fair Value Remeasurement of Contingent Consideration | $ 800 |  |
Kolltan | Specified development, regulatory approvals or sales-based milestones |  |  |
Fair value measurements |  |  |
Milestone payments |  |  | $ 172,500
Fair value |  |  |
Fair value measurements |  |  |
Assets level 1 to level 2 transfers | 0 | $ 0 |
Assets level 2 to level 1 transfers | 0 | 0 |
Liabilities level 1 to level 2 transfers | 0 | 0 |
Liabilities level 2 to level 1 transfers | 0 | 0 |
Asset transfer out of level 3 | 0 | 0 |
Asset transfer into level 3 | 0 | 0 |
Liabilities transfers out of level 3 | 0 | 0 |
Liabilities transfers into level 3 | $ 0 | $ 0 |

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- Definition Amount of increase (decrease) in the value of a contingent consideration liability, including, but not limited to, differences arising upon settlement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 4 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e7008-128479 + Details
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- Definition For contingent consideration arrangements recognized in connection with a business combination, this element represents an estimate of the high-end of the potential range (undiscounted) of the consideration which may be paid. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479 + Details
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- Definition Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bb) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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- Definition Amount of transfers of liabilities measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bb) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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