Revenue Recognition - Additional Information (Detail) - USD ($)	1 Months Ended					3 Months Ended		9 Months Ended		12 Months Ended
	Oct. 31, 2016	Mar. 31, 2016	Feb. 29, 2016	Jul. 31, 2014	Jan. 31, 2014	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2016	Jan. 01, 2018	Dec. 31, 2017
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue						$ 14,177,000	$ 3,828,000	$ 24,832,000	$ 12,743,000
Costs to obtain or fulfill the contract capitalized						0		0
Contract liabilities						7,443,000		7,443,000				$ 7,623,000
Unbilled - collaboration and license revenue						9,872,000		9,872,000			$ 6,694,000
Deferred revenue
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liabilities						7,443,000		7,443,000				$ 7,623,000
Topic 606 | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Unbilled - collaboration and license revenue						9,872,000		9,872,000			$ 6,694,000
BMS and Pfizer
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee					$ 13,000,000
Milestone payments of development and regulatory event					$ 12,000,000
Percentage of consideration received under agreement					50.00%
BMS and Pfizer | 2016 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Non-refundable upfront fee										$ 15,000,000
Contingent payment receivable upon achievement of regulatory events										20,000,000
Contingent payment receivable upon achievement of annual net sales volumes										$ 70,000,000
BMS and Pfizer | 2016 Agreement | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received								$ 15,000,000
BMS and Pfizer | 2016 Agreement | Accounting Standards Update 2014-09 | Ethnic Sensitivity Study
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage								33.00%
BMS and Pfizer | 2016 Agreement | Accounting Standards Update 2014-09 | Factor Xa Inhibitors Other Than Apixaban
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage								66.00%
BMS and Pfizer | 2016 Agreement | Topic 606 | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Transaction price								$ 13,100,000
Costs to obtain or fulfill the contract						0		0
Upfront payment						15,000,000		15,000,000
BMS and Pfizer | 2016 Agreement | Topic 606 | Accounting Standards Update 2014-09 | Deferred revenue
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liabilities						7,400,000		$ 7,400,000
BMS and Pfizer | 2016 Agreement | Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of royalties entitle to receive under agreement								5.00%
BMS and Pfizer | 2016 Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of royalties entitle to receive under agreement								15.00%
BMS and Pfizer | 2014 Agreement | Topic 606 | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Transaction price								$ 16,500,000
Percentage of refundable transaction price								50.00%
Additional payments eligible to be earned								$ 0
Costs to obtain or fulfill the contract						0		0
BMS and Pfizer | 2014 Agreement | Topic 606 | Accounting Standards Update 2014-09 | Deferred revenue
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liabilities						100,000		100,000
Daiichi Sankyo, Inc ("Daiichi") | 2016 Agreement | Topic 606 | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Costs to obtain or fulfill the contract capitalized						0		0
Transaction price								15,300,000
Upfront payment						5,000,000		5,000,000
Estimated variable consideration transaction price						5,900,000		5,900,000
Regulatory milestone payments								10,000,000
Daiichi Sankyo, Inc ("Daiichi") | 2016 Agreement | Topic 606 | Accounting Standards Update 2014-09 | Ethnic Sensitivity Study
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Estimated variable consideration transaction price						4,400,000		4,400,000
Daiichi Sankyo, Inc ("Daiichi") | 2016 Agreement | Topic 606 | Accounting Standards Update 2014-09 | Deferred revenue
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Unbilled - collaboration and license revenue						3,300,000		3,300,000
Daiichi Sankyo, Inc ("Daiichi") | 2014 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee				$ 15,000,000
Milestone payments of development and regulatory event				20,000,000
Contingent payment receivable upon achievement				$ 5,000,000
Daiichi Sankyo, Inc ("Daiichi") | October 2016 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee	$ 15,000,000
Milestone payments of development and regulatory event	$ 2,500,000
Percentage of consideration received under agreement	1.00%
Contingent payment receivable upon achievement of annual net sales volumes	$ 8,000,000
Contingent payment receivable upon achievement	$ 10,000,000
Daiichi Sankyo, Inc ("Daiichi") | March 2016 Agreement | Ethnic Sensitivity Study
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage		33.00%
Daiichi Sankyo, Inc ("Daiichi") | March 2016 Agreement | Minimum | Edoxaban
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage		33.00%
Daiichi Sankyo, Inc ("Daiichi") | March 2016 Agreement | Maximum | Edoxaban
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage		100.00%
Daiichi Sankyo, Inc ("Daiichi") | 2014 and October 2016 Amendment | Topic 606 | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Transaction price								34,000,000
Costs to obtain or fulfill the contract						0		0
Upfront payment						22,000,000		22,000,000
Milestones already received on achieving performance obligations								9,000,000
Milestone payments eligible for achievement of certain events								3,000,000
Milestone payments eligible for achievement								5,500,000
Daiichi Sankyo, Inc ("Daiichi") | 2014 and October 2016 Amendment | Topic 606 | Accounting Standards Update 2014-09 | Deferred revenue
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Unbilled - collaboration and license revenue						1,100,000		1,100,000
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | 2014 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee					$ 10,000,000
Milestone payments of development and regulatory event					8,000,000
Contingent payment receivable upon achievement					$ 7,000,000
Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | 2014 Agreement | Topic 606 | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Costs to obtain or fulfill the contract capitalized						0		0
Transaction price								25,000,000
Upfront payment						10,000,000		10,000,000
Milestone payments eligible for achievement								0
Unbilled - collaboration and license revenue						1,900,000		1,900,000
Milestones already received on achieving performance obligations								13,000,000
Probable milestone payment to be achieved								2,000,000
Bayer Pharma AG | 2016 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee			$ 5,000,000
Contingent payment receivable upon achievement			10,000,000
Reduced contingent payment receivable upon achievement			$ 7,000,000
Bayer Pharma AG | 2016 Agreement | Ethnic Sensitivity Study
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage			33.00%
Bayer Pharma AG | 2016 Agreement | Topic 606 | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Transaction price								15,300,000
Costs to obtain or fulfill the contract						0		0
Upfront payment						5,000,000		5,000,000
Milestone payments eligible for achievement								10,000,000
Unbilled - collaboration and license revenue						3,700,000		3,700,000
Estimated variable consideration transaction price						5,900,000		5,900,000
Bayer Pharma AG | 2016 Agreement | Topic 606 | Accounting Standards Update 2014-09 | Ethnic Sensitivity Study
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Estimated variable consideration transaction price						4,400,000		4,400,000
Bayer Pharma AG | 2016 Agreement | Minimum | Rivaroxaban
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage			33.00%
Bayer Pharma AG | 2016 Agreement | Maximum | Rivaroxaban
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reimbursement of costs and expenses percentage			100.00%
Chargebacks and Returns
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reduction to revenue						(800,000)		(3,000,000)
Royalty
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue								0
Collaboration and License Revenue
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue						7,001,000	$ 3,828,000	14,785,000	$ 12,743,000
Collaboration and License Revenue | Topic 606 | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue						5,415,000		5,274,000
Collaboration and License Revenue | BMS and Pfizer | 2016 Agreement | Topic 606 | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue						1,300,000		700,000
Collaboration and License Revenue | BMS and Pfizer | 2014 Agreement | Topic 606 | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue						100,000		1,400,000
Collaboration and License Revenue | Daiichi Sankyo, Inc ("Daiichi") | 2016 Agreement | Topic 606 | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue						1,900,000		3,100,000
Collaboration and License Revenue | Daiichi Sankyo, Inc ("Daiichi") | 2014 and October 2016 Amendment | Topic 606 | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue						1,800,000		2,500,000
Collaboration and License Revenue | Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | 2014 Agreement | Topic 606 | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue						100,000		4,000,000
Collaboration and License Revenue | Bayer Pharma AG | 2016 Agreement | Topic 606 | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue						1,900,000		3,000,000
New Drug Application | BMS and Pfizer | 2016 Agreement | Topic 606 | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Estimated variable consideration transaction price								4,400,000
New Drug Application | BMS and Pfizer | 2016 Agreement | Topic 606 | Accounting Standards Update 2014-09 | Japan
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment						$ 5,000,000		5,000,000
Phase Four Clinical Trial | BMS and Pfizer | 2016 Agreement | Topic 606 | Accounting Standards Update 2014-09 | Japan
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Estimated variable consideration transaction price								600,000
Decrease in transaction price								$ 11,900,000