Revenue, Credit Concentrations and Geographic Information - Disaggregates of Total Net Product Revenues Based on Patient Location (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Net product revenues	$ 387,763	$ 372,845	$ 788,508	$ 746,292
United States
Disaggregation of Revenue [Line Items]
Net product revenues	169,407	162,789	360,343	353,360
Europe
Disaggregation of Revenue [Line Items]
Net product revenues	119,561	107,221	244,100	212,871
Latin America
Disaggregation of Revenue [Line Items]
Net product revenues	46,494	38,152	80,333	76,555
Rest of world
Disaggregation of Revenue [Line Items]
Net product revenues	52,301	64,683	103,732	103,506
Aldurazyme
Disaggregation of Revenue [Line Items]
Net product revenues	5,826	24,003	51,093	90,059
Total net product revenues
Disaggregation of Revenue [Line Items]
Net product revenues	379,075	367,786	773,558	736,885
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim
Disaggregation of Revenue [Line Items]
Net product revenues	373,249	343,783	722,465	646,826
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | United States
Disaggregation of Revenue [Line Items]
Net product revenues	160,918	138,411	305,203	262,552
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | Europe
Disaggregation of Revenue [Line Items]
Net product revenues	113,593	102,621	236,678	207,419
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | Latin America
Disaggregation of Revenue [Line Items]
Net product revenues	46,493	48,844	80,333	76,555
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | Rest of world
Disaggregation of Revenue [Line Items]
Net product revenues	52,245	53,907	100,251	100,300
Marketed by Genzyme | Aldurazyme
Disaggregation of Revenue [Line Items]
Net product revenues	$ 5,826	$ 24,003	$ 51,093	$ 90,059