Quarterly Financial Data (unaudited) Quarterly Financial Data (unaudited) Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended								12 Months Ended
	Dec. 31, 2018	Jul. 30, 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, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Collaborative Arrangement Agreements [Line Items]
Intangible asset impairment charges			$ 29,000,000	$ 0	$ 0	$ 0	$ 0	$ 255,340,000	$ 0	$ 0	$ 29,000,000	$ 255,340,000	$ 0
Income tax (benefit) resulting in the release of valuation allowance			(1,560,000,000)
Provision for (benefit from) income taxes			$ (1,492,599,000)	$ 8,055,000	$ 10,341,000	(12,659,000)	10,257,000	(125,903,000)	4,337,000	3,985,000	(1,486,862,000)	(107,324,000)	16,665,000
Merck KGaA and Arbor
Schedule of Collaborative Arrangement Agreements [Line Items]
Collaborative arrangement, development and commercialization rights potential maximum milestone payments								95,000,000
BioAxone Biosciences, Inc
Schedule of Collaborative Arrangement Agreements [Line Items]
Up-front payment						$ 10,000,000					10,000,000				$ 10,000,000
Merck KGaA
Schedule of Collaborative Arrangement Agreements [Line Items]
Up-front payment	$ 65,000,000									$ 230,000,000.0
Parion Sciences, Inc
Schedule of Collaborative Arrangement Agreements [Line Items]
Up-front payment											85,000,000			$ 85,000,000
Collaborative revenues								20,000,000	$ 20,000,000
Intangible asset impairment charges								255,300,000
Business combination, contingent consideration arrangements, change in amount of contingent consideration, liability								(69,600,000)
Provision for (benefit from) income taxes								(126,200,000)
Janssen
Schedule of Collaborative Arrangement Agreements [Line Items]
Up-front payment															$ 35,000,000
Collaborative revenues							$ 25,000,000
Concert Pharmaceuticals
Schedule of Collaborative Arrangement Agreements [Line Items]
Collaborative arrangement, development and commercialization rights potential maximum milestone payments		$ 160,000,000						160,000,000
Variable Interest Entity, Primary Beneficiary
Schedule of Collaborative Arrangement Agreements [Line Items]
Business combination, contingent consideration arrangements, change in amount of contingent consideration, liability											17,730,000	(62,560,000)	54,850,000
Provision for (benefit from) income taxes											(3,668,000)	(114,090,000)	16,743,000
Variable Interest Entity, Primary Beneficiary | BioAxone Biosciences, Inc
Schedule of Collaborative Arrangement Agreements [Line Items]
Business combination, contingent consideration arrangements, change in amount of contingent consideration, liability												900,000	(9,950,000)
Variable Interest Entity, Primary Beneficiary | Parion Sciences, Inc
Schedule of Collaborative Arrangement Agreements [Line Items]
Collaborative revenues												40,000,000
Business combination, contingent consideration arrangements, change in amount of contingent consideration, liability											0	(63,460,000)	$ 64,800,000
Provision for (benefit from) income taxes												14,800,000
Other Intangible Assets | Variable Interest Entity, Primary Beneficiary | BioAxone Biosciences, Inc
Schedule of Collaborative Arrangement Agreements [Line Items]
Intangible asset impairment charges								29,000,000
Provision for (benefit from) income taxes											$ (7,900,000)
Other Intangible Assets | Variable Interest Entity, Primary Beneficiary | Parion Sciences, Inc
Schedule of Collaborative Arrangement Agreements [Line Items]
Intangible asset impairment charges								$ 255,300,000				255,300,000
Provision for (benefit from) income taxes												$ (97,700,000)