Income taxes - reconciliations between statutory federal income tax rate and effective income tax rate (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal statutory rate	21.00%	21.00%	35.00%
Tax effect of international items	(11.30%)	(3.30%)	(25.70%)
Impacts of the TCJA	0	(0.010)	0.379
Legal entity merger - deferred taxes	(38.00%)	0.00%	0.00%
Excess tax benefits related to share-based compensation	(4.50%)	(7.20%)	(2.30%)
State taxes, net of federal benefit	(4.90%)	(0.10%)	0.10%
Uncertain tax contingencies	0.00%	(0.40%)	(1.80%)
Contingent consideration	3.40%	5.30%	0.40%
Intellectual property impairment charge	0.00%	(2.00%)	0.00%
Research and development tax credit	(1.10%)	(1.60%)	(0.80%)
Other, net	(0.50%)	(0.10%)	2.70%
Effective income tax rate, total	(35.90%)	10.60%	45.50%
Increase (decrease) in deferred tax liability due to merger of foreign subsidiaries	$ (129)