Collaborative arrangements - Changes in Balances of Company's Receivables and Contract Liabilities (Detail) - Celgene Corporation [Member] $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($)
Receivables
Balance at beginning of period	$ 6,528
Additions	10,450
Deductions	(6,528)
Balance at end of period	10,450
Contract liabilities:
Balance at beginning of period	34,939
Additions	10,000
Deductions	(21,716)
Balance at end of period	23,223
Accrued Expenses [Member]
Contract liabilities:
Additions	3,781
Balance at end of period	$ 3,781