Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Valuation Allowance [Line Items]
Non-US Net operating loss carryforwards	$ 526,100,000
Operating loss carryforwards expiration period	2022
Unrecognized tax benefits, gross	$ 5,231,000	$ 1,595,000	$ 354,000	$ 163,000
Unrecognized tax benefits would favorably impact the effective tax rate if recognized	4,800,000
Accrued interest or penalties related to uncertain tax positions	0	0	0
Uncertain tax positions recognized	0	$ 0	$ 0
U.S. Domestic Federal [Member] | Research and Development [Member]
Valuation Allowance [Line Items]
Tax credit carryforward amount	$ 4,400,000
Tax credit carryforward, expiration year	2039
Uncertain tax positions	$ 3,000,000.0
U.S. Domestic State [Member] | Research and Development [Member]
Valuation Allowance [Line Items]
Tax credit carryforward amount	$ 3,400,000
Tax credit carryforward, expiration year	2034
Uncertain tax positions	$ 2,200,000
Switzerland [Member]
Valuation Allowance [Line Items]
Increase in valuation allowance	9,700,000
Non-US Net operating loss carryforwards	262,300,000
Canton of Zug [Member]
Valuation Allowance [Line Items]
Non-US Net operating loss carryforwards	262,300,000
UNITED KINGDOM [Member]
Valuation Allowance [Line Items]
Non-US Net operating loss carryforwards	$ 1,500,000