Revenue, Credit Concentrations and Geographic Information - Disaggregates of Total Net Product Revenues Based on Patient Location (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Net product revenues	$ 461,097	$ 391,706	$ 1,249,605	$ 1,137,998
United States
Disaggregation of Revenue [Line Items]
Net product revenues	201,874	174,722	562,217	528,082
Europe
Disaggregation of Revenue [Line Items]
Net product revenues	125,485	111,069	369,585	323,940
Latin America
Disaggregation of Revenue [Line Items]
Net product revenues	83,799	75,400	164,132	151,955
Rest of world
Disaggregation of Revenue [Line Items]
Net product revenues	49,939	30,515	153,671	134,021
Aldurazyme
Disaggregation of Revenue [Line Items]
Net product revenues	22,852	27,593	73,945	117,652
Total net product revenues
Disaggregation of Revenue [Line Items]
Net product revenues	450,900	386,320	1,224,458	1,123,205
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim
Disaggregation of Revenue [Line Items]
Net product revenues	428,048	358,727	1,150,513	1,005,553
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | United States
Disaggregation of Revenue [Line Items]
Net product revenues	175,127	146,742	480,330	409,294
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | Europe
Disaggregation of Revenue [Line Items]
Net product revenues	121,363	107,851	358,041	315,270
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | Latin America
Disaggregation of Revenue [Line Items]
Net product revenues	83,799	75,400	164,132	151,955
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | Rest of world
Disaggregation of Revenue [Line Items]
Net product revenues	47,759	28,734	148,010	129,034
Marketed by Genzyme | Aldurazyme
Disaggregation of Revenue [Line Items]
Net product revenues	$ 22,852	$ 27,593	$ 73,945	$ 117,652