Commitments and Contingencies - Additional Information (Detail)			1 Months Ended
	Apr. 18, 2018 USD ($) shares	Apr. 29, 2016 USD ($)	Dec. 31, 2017 USD ($)	Mar. 31, 2018 USD ($)	Apr. 30, 2016 a
Commitments And Contingencies [Line Items]
Property, plant and equipment, net			$ 181,900,000	$ 201,979,000
Restricted investments			30,000,000	30,000,000
Dicerna Pharmaceuticals, Inc | Subsequent Event
Commitments And Contingencies [Line Items]
Litigation settlement, settlement agreement date	April 18, 2018
Litigation settlement amount	$ 25,000,000
Upfront cash payment received	$ 2,000,000
Litigation settlement, common stock issuable from other party | shares	983,208
Litigation settlement, common stock value	$ 10,000,000
Remaining settlement amount	$ 13,000,000
Litigation settlement payment period	4 years
Dicerna Pharmaceuticals, Inc | Subsequent Event | Minimum | Oligonucleotide
Commitments And Contingencies [Line Items]
Restriction period in development and other activities defined set of targets	18 months
Dicerna Pharmaceuticals, Inc | Subsequent Event | Maximum | Oligonucleotide
Commitments And Contingencies [Line Items]
Restriction period in development and other activities defined set of targets	4 years
Bank of America N.A
Commitments And Contingencies [Line Items]
Cash collateral required for principal amount outstanding, percentage		100.00%
Bank of America N.A | Term Loan Facility
Commitments And Contingencies [Line Items]
Line of credit facility, maximum borrowing capacity		$ 120,000,000
Repayment of outstanding principal amount in full			120,000,000
Line of credit facility, expiration date		Apr. 29, 2021
Bank of America N.A | Term Loan Facility | LIBOR
Commitments And Contingencies [Line Items]
Debt instrument, basis spread on variable rate		0.45%
Wells Fargo Bank, National Association
Commitments And Contingencies [Line Items]
Cash collateral required for principal amount outstanding, percentage		100.00%
Wells Fargo Bank, National Association | Term Loan Facility
Commitments And Contingencies [Line Items]
Line of credit facility, maximum borrowing capacity		$ 30,000,000
Line of credit facility, expiration date		Apr. 29, 2021
Wells Fargo Bank, National Association | Term Loan Facility | LIBOR
Commitments And Contingencies [Line Items]
Debt instrument, basis spread on variable rate		0.45%
Norton, Massachusetts
Commitments And Contingencies [Line Items]
Undeveloped land acquired | a					12
Norton, Massachusetts | Land and costs related to the construction of manufacturing facility
Commitments And Contingencies [Line Items]
Property, plant and equipment, net			$ 140,500,000	$ 158,200,000