Collaborative arrangements - Changes in Balances of Company's Receivables and Contract Liabilities (Detail) - Bristol-Myers Squibb $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Receivables
Balance at beginning of period	$ 400
Additions	2,400
Deductions	400
Balance at end of period	2,400
Contract liabilities:
Balance at beginning of period	18,265
Additions	0
Deductions	2,118
Balance at end of period	$ 16,147