Disaggregates of Total Net Product Revenues Based on Patient Location (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation Of Revenue [Line Items]
Net product revenues	$ 372,845	$ 317,448	$ 746,292	$ 621,193
United States
Disaggregation Of Revenue [Line Items]
Net product revenues	162,788	141,611	353,360	274,095
Europe
Disaggregation Of Revenue [Line Items]
Net product revenues	107,221	87,672	212,871	171,577
Latin America
Disaggregation Of Revenue [Line Items]
Net product revenues	58,158	66,739	96,633	112,035
Rest of World
Disaggregation Of Revenue [Line Items]
Net product revenues	44,678	21,426	83,428	63,486
Aldurazyme
Disaggregation Of Revenue [Line Items]
Net product revenues	24,003	19,985	90,059	39,340
Net Product Revenues
Disaggregation Of Revenue [Line Items]
Net product revenues	367,786	315,926	736,885	618,116
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim
Disaggregation Of Revenue [Line Items]
Net product revenues	343,783	295,941	646,826	578,776
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | United States
Disaggregation Of Revenue [Line Items]
Net product revenues	138,411	121,256	262,552	233,962
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | Europe
Disaggregation Of Revenue [Line Items]
Net product revenues	104,262	87,672	207,419	171,577
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | Latin America
Disaggregation Of Revenue [Line Items]
Net product revenues	58,158	66,738	96,633	112,032
Marketed by Company | Brineura, Firdapse, Kuvan, Naglazyme, and Vimizim | Rest of World
Disaggregation Of Revenue [Line Items]
Net product revenues	42,952	20,275	80,222	61,205
Marketed by Genzyme | Aldurazyme
Disaggregation Of Revenue [Line Items]
Net product revenues	$ 24,003	$ 19,985	$ 90,059	$ 39,340