Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation Allowance [Line Items]
Corporate tax rate	9.30%	9.30%	10.30%
Non-US Net operating loss carryforwards	$ 541,100,000
Operating loss carryforwards expiration period	2020
Domestic state research and development credit carryforwards	$ 1,800,000
Research and development credit carryforwards expiration period	2033
Uncertain tax positions	$ 700,000
Unrecognized tax benefits, gross	1,595,000	$ 354,000	$ 163,000	$ 49,000
Unrecognized tax benefits would favorably impact the effective tax rate if recognized	1,500,000
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]
Uncertain tax positions	900,000
Tax credit carryforward amount	$ 1,900,000
Tax credit carryforward, expiration year	2038
Maximum [Member]
Valuation Allowance [Line Items]
Corporate tax rate	21.00%	35.00%
Switzerland [Member]
Valuation Allowance [Line Items]
Increase in valuation allowance	$ 23,200,000