Disaggregates of Total Net Product Revenues Based on Patient Location (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Net product revenues	$ 1,704,048	$ 1,491,212	$ 1,313,646
United States
Disaggregation of Revenue [Line Items]
Net product revenues	778,440	696,793	588,243
Europe
Disaggregation of Revenue [Line Items]
Net product revenues	509,188	436,434	398,814
Latin America
Disaggregation of Revenue [Line Items]
Net product revenues	218,792	185,046	181,970
Rest of world
Disaggregation of Revenue [Line Items]
Net product revenues	197,628	172,939	144,619
Aldurazyme
Disaggregation of Revenue [Line Items]
Net product revenues	97,809	135,097	89,959
Product
Disaggregation of Revenue [Line Items]
Net product revenues	1,661,043	1,470,356	1,270,445
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim
Disaggregation of Revenue [Line Items]
Net product revenues	1,563,234	1,335,259	1,180,486
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | United States
Disaggregation of Revenue [Line Items]
Net product revenues	669,171	560,030	495,741
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | Europe
Disaggregation of Revenue [Line Items]
Net product revenues	485,596	424,357	363,538
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | Latin America
Disaggregation of Revenue [Line Items]
Net product revenues	218,792	184,984	181,963
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | Rest of world
Disaggregation of Revenue [Line Items]
Net product revenues	189,675	165,888	139,244
Marketed by Genzyme | Aldurazyme
Disaggregation of Revenue [Line Items]
Net product revenues	$ 97,809	$ 135,097	$ 89,959