Revenue Recognition - Additional Information (Detail) - USD ($)	1 Months Ended				3 Months Ended		12 Months Ended
	Oct. 31, 2016	Mar. 31, 2016	Feb. 29, 2016	Jul. 31, 2014	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2016	Dec. 31, 2018
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue					$ 22,169,000	$ 6,644,000
Costs to obtain or fulfill the contract capitalized					0
Contract liabilities					6,638,000			$ 6,335,000
Unbilled - collaboration and license revenue					6,317,000			9,880,000
Deferred revenue
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liabilities					6,638,000			$ 6,335,000
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 | Topic 606 | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Transaction price					12,900,000
Upfront payment					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					$ 5,500,000
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%
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
Transaction price					15,500,000
Upfront payment					5,000,000
Estimated variable consideration transaction price					6,200,000
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					4,300,000
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					3,000,000
Daiichi Sankyo, Inc ("Daiichi") | 2014 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee				$ 15,000,000
Contingent payment receivable upon achievement				5,000,000
Milestone payments of development and regulatory event				$ 20,000,000
Daiichi Sankyo, Inc ("Daiichi") | October 2016 Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent payment receivable upon achievement of annual net sales volumes	$ 8,000,000
Upfront fee	15,000,000
Contingent payment receivable upon achievement	10,000,000
Milestone payments of development and regulatory event	$ 2,500,000
Percentage of consideration received under agreement	1.00%
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
Upfront payment					22,000,000
Milestones already received on achieving performance obligations					12,000,000
Milestone payments eligible for achievement					5,500,000
Costs to obtain or fulfill the contract					0
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]
Contract liabilities					1,100,000
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
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					15,500,000
Upfront payment					5,000,000
Milestone payments eligible for achievement					10,000,000
Costs to obtain or fulfill the contract					0
Estimated variable consideration transaction price					6,200,000
Unbilled - collaboration and license revenue					3,300,000
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					4,300,000
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%
Distribution Fees and Reserves for Cargebacks and Returns
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Reduction to revenue					(2,400,000)
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					1,807,000	$ 6,038,000
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					200,000
Collaboration and License Revenue | BMS and Pfizer | 2014 Agreement | Maximum | Topic 606 | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue					100,000
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					600,000
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					500,000
Collaboration and License Revenue | Bayer Pharma, AG ('Bayer") and Janssen Pharmaceuticals, Inc. ("Janssen") | 2014 Agreement | Maximum | Topic 606 | Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and license revenue					100,000
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					500,000
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
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]
Costs on clinical trial					600,000
Decrease in transaction price					$ 12,100,000