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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Net product revenues	$ 476,784	$ 461,097	$ 1,408,338	$ 1,249,605
United States
Disaggregation of Revenue [Line Items]
Net product revenues	252,948	201,874	729,672	562,217
Europe
Disaggregation of Revenue [Line Items]
Net product revenues	121,158	125,485	375,453	369,585
Latin America
Disaggregation of Revenue [Line Items]
Net product revenues	44,064	83,799	141,852	164,132
Rest of world
Disaggregation of Revenue [Line Items]
Net product revenues	58,614	49,939	161,361	153,671
Total net product revenues
Disaggregation of Revenue [Line Items]
Net product revenues	460,741	450,900	1,368,816	1,224,458
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, Palynziq, and Vimizim
Disaggregation of Revenue [Line Items]
Net product revenues	419,754	428,048	1,239,871	1,150,513
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, Palynziq, and Vimizim | United States
Disaggregation of Revenue [Line Items]
Net product revenues	203,892	175,127	582,734	480,330
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, Palynziq, and Vimizim | Europe
Disaggregation of Revenue [Line Items]
Net product revenues	115,548	121,363	360,718	358,041
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, Palynziq, and Vimizim | Latin America
Disaggregation of Revenue [Line Items]
Net product revenues	44,064	83,799	141,852	164,132
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, Palynziq, and Vimizim | Rest of world
Disaggregation of Revenue [Line Items]
Net product revenues	56,250	47,759	154,567	148,010
Marketed by Company | Total net product revenues
Disaggregation of Revenue [Line Items]
Net product revenues	419,754	428,048	1,239,871	1,150,513
Marketed by Genzyme | Aldurazyme
Disaggregation of Revenue [Line Items]
Net product revenues	$ 40,987	$ 22,852	$ 128,945	$ 73,945