Purchase Commitments - Additional Information (Detail)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($) Batch
Long Term Purchase Commitment [Line Items]
Accounts payables	$ 11,938,000	$ 11,938,000	$ 14,546,000
Prepaid expenses and other current assets	12,330,000	12,330,000	2,680,000
Prepaid and other long-term assets	6,277,000	$ 6,277,000	$ 5,214,000
CMC ICOS Biologics Inc
Long Term Purchase Commitment [Line Items]
Number of batches to be manufactured, 2017 | Batch			20
Non-refundable manufacturing reservation payments committed			$ 2,500,000
Purchase commitment, description		We have made firm orders to manufacture 20 batches in 2017 and are required to make a non-refundable manufacturing reservation payment of $2.5 million for ten batches to be manufactured in 2018 contingent upon CMC’s successful delivery of services related to our BLA re-submission to the FDA
Number of batches to be manufactured, 2018 | Batch			10
Purchase obligation services received		$ 33,700,000
Repayment of accounts payable and accrued liabilities	1,500,000	5,300,000
Accounts payables	300,000	300,000
Prepaid manufacturing services	1,000,000	1,000,000
Hovione, Limited
Long Term Purchase Commitment [Line Items]
Prepaid expenses and other current assets	6,200,000	6,200,000
Prepaid and other long-term assets	$ 6,300,000	6,300,000
Hovione, Limited | Maximum
Long Term Purchase Commitment [Line Items]
Cancellable and non-cancellable additional purchase commitments		$ 15,200,000