Commitments and Contingencies - Additional Information (Detail) € in Millions		1 Months Ended	3 Months Ended				12 Months Ended
	May 08, 2017 USD ($)	Apr. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($) $ / SFr $ / €	Mar. 31, 2020 CHF (SFr)	Mar. 31, 2020 EUR (€)	Dec. 31, 2019 USD ($) $ / SFr	Dec. 31, 2019 CHF (SFr) $ / SFr	Dec. 31, 2017 USD ($) $ / SFr	Dec. 31, 2017 CHF (SFr) $ / SFr	Mar. 31, 2020 CHF (SFr) $ / SFr $ / €
Loss Contingencies [Line Items]
Upfront cash payments				$ 105,200,000
River Vision [Member]
Loss Contingencies [Line Items]
Maximum payment to be made upon attainment of milestones				$ 325,000,000.0
Upfront cash payments	$ 150,300,000
Percentage of net sales in earn-out payment				3.00%	3.00%	3.00%
Net sales minimum limit for royal payment				$ 300,000,000.0
River Vision [Member] | FDA Approval [Member]
Loss Contingencies [Line Items]
Maximum payment to be made upon attainment of milestones				100,000,000.0
Upfront cash payments				100,000,000.0
RAVICTI, BUPHENYL, RAYOS and QUINSAIR [Member]
Loss Contingencies [Line Items]
Purchase and other commitments outstanding purchase orders				8,800,000
Teprotumumab [Member] | River Vision [Member] | Net Sales Thresholds [Member]
Loss Contingencies [Line Items]
Maximum payment to be made upon attainment of milestones				225,000,000.0
AGC Biologics A/S [Member] | TEPEZZA [Member]
Loss Contingencies [Line Items]
Minimum binding purchase commitment				$ 64,300,000		€ 58.3
Currency exchange rate | $ / €				1.1034							1.1034
Catalent [Member] | TEPEZZA Drug Product [Member]
Loss Contingencies [Line Items]
Minimum binding purchase commitment				$ 8,400,000
Patheon Pharmaceuticals Inc. [Member] | PROCYSBI Developed Technology [Member]
Loss Contingencies [Line Items]
Minimum binding purchase commitment				$ 1,400,000
Supply agreement expiry date				Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2021
Cambrex [Member] | PROCYSBI API [Member]
Loss Contingencies [Line Items]
Minimum binding purchase commitment				$ 700,000
Supply agreement expiry date				Nov. 02, 2020	Nov. 02, 2020	Nov. 02, 2020
Boehringer Ingelheim [Member] | ACTIMMUNE Developed Technology [Member]
Loss Contingencies [Line Items]
Minimum binding purchase commitment				$ 15,400,000
Currency exchange rate | $ / €				1.1034							1.1034
Additional costs committed to be incurred for harmonization of drug substance manufacturing process				$ 400,000
Bio-Technology General (Israel) Ltd [Member] | KRYSTEXXA Developed Technology [Member]
Loss Contingencies [Line Items]
Minimum binding purchase commitment				$ 38,000,000.0
Supply agreement expiry date				Dec. 31, 2030	Dec. 31, 2030	Dec. 31, 2030
Term of agreement automatically renewal period				3 years	3 years	3 years
Written notice period for termination of agreement				3 years	3 years	3 years
Expected early termination period of agreement due to uncertain event				Jan. 01, 2024	Jan. 01, 2024	Jan. 01, 2024
Purchase commitment outstanding purchase orders				$ 1,200,000
Bio-Technology General (Israel) Ltd [Member] | KRYSTEXXA Developed Technology [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Purchase obligation percentage				80.00%	80.00%	80.00%
Nuvo Pharmaceuticals Inc. [Member] | PENNSAID 2% [Member]
Loss Contingencies [Line Items]
Minimum binding purchase commitment				$ 3,800,000
Supply agreement expiry date				Dec. 31, 2029	Dec. 31, 2029	Dec. 31, 2029
Sanofi-Aventis U.S [Member] | DUEXIS [Member]
Loss Contingencies [Line Items]
Minimum binding purchase commitment				$ 9,000,000.0
Term of agreement automatically renewal period				2 years	2 years	2 years
Written notice period for termination of agreement				2 years	2 years	2 years
Term of agreement expiration month and year				2021-05	2021-05	2021-05
S.R. One [Member] | Subsequent Event [Member]
Loss Contingencies [Line Items]
One-time payment in exchange of milestone and royalty payments		$ 55,000,000.0
Lundbeckfond [Member] | Subsequent Event [Member]
Loss Contingencies [Line Items]
One-time payment in exchange of milestone and royalty payments		$ 55,000,000.0
S.R. One and Lundbeckfond [Member] | Scenario Forecast [Member] | TEPEZZA Developed Technology [Member]
Loss Contingencies [Line Items]
Payments to acquire intangible assets			$ 110,000,000.0
S.R. One and Lundbeckfond [Member] | River Vision [Member] | Subsequent Event [Member]
Loss Contingencies [Line Items]
Percentage of right to receive payments		35.66%
Percentage of remaining net obligations payments		71.32%
Roche [Member]
Loss Contingencies [Line Items]
Currency exchange rate | $ / SFr				1.0382							1.0382
Maximum payment to be made upon attainment of milestones				$ 107,200,000							SFr 103,000,000.0
Milestone incurred				$ 5,200,000	SFr 5,000,000.0
Roche [Member] | TEPEZZA [Member]
Loss Contingencies [Line Items]
Currency exchange rate | $ / SFr				1.0406			1.0023	1.0023	1.0169	1.0169	1.0406
Milestone incurred							$ 3,000,000.0	SFr 3,000,000.0	$ 2,000,000.0	SFr 2,000,000.0
Roche [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Percentage of net sales in earn-out payment				9.00%	9.00%	9.00%
Roche [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Percentage of net sales in earn-out payment				12.00%	12.00%	12.00%
Lundquist Institute [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Percentage of net sales in earn-out payment				1.00%	1.00%	1.00%