Income Taxes - Reconciliation of the Federal Statutory Rate to Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Federal income tax rate	34.00%	34.00%	34.00%
Foreign rate differential	182.70%	(49.60%)	151.50%
State tax, net of federal benefit	10.10%	13.40%	(0.90%)
Permanent Items:
Incentive stock options	(2.50%)	1.00%	(14.90%)
Dividend from foreign subsidiary	(165.80%)	53.50%	(79.80%)
Amortization of technical rights	(0.00%)	(34.50%)	23.40%
Deferred adjustments	15.90%	30.60%	6.60%
Foreign research and development relief	26.30%	0.00%	0.00%
Change in U.S. Federal rate	(970.40%)	0.00%	0.00%
Other	(2.60%)	(1.10%)	(0.50%)
Effect of permanent differences	(1099.10%)	49.50%	(65.20%)
Effective income tax rate	(872.30%)	47.30%	119.40%
Change in valuation allowance	880.60%	(45.80%)	(119.70%)
Effective income tax rate	8.30%	1.50%	(0.30%)