Commitments and Contingencies - Summary of Remaining Aggregate Potential Milestone Payments Payable Based on Achievement of Net Sales Thresholds (Detail) - River Vision [Member]	Mar. 31, 2020 USD ($)
Loss Contingencies [Line Items]
Milestone Payment	$ 325,000,000.0
Net Sales Thresholds [Member] | Teprotumumab [Member]
Loss Contingencies [Line Items]
Milestone Payment	225,000,000.0
TEPEZZA Worldwide Net Sales Threshold >$250 million [Member] | Net Sales Thresholds [Member] | Teprotumumab [Member]
Loss Contingencies [Line Items]
Milestone Payment	50,000,000
TEPEZZA Worldwide Net Sales Threshold >$375 million [Member] | Net Sales Thresholds [Member] | Teprotumumab [Member]
Loss Contingencies [Line Items]
Milestone Payment	75,000,000
TEPEZZA Worldwide Net Sales Threshold >$500million [Member] | Net Sales Thresholds [Member] | Teprotumumab [Member]
Loss Contingencies [Line Items]
Milestone Payment	$ 100,000,000