Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2014
Income Taxes Disclosure [Line Items]
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	$ 13,400,000
Deferred Tax Assets, Valuation Allowance	1,830,000	$ 15,204,000
Unrecognized Tax Benefits	15,245,000	9,565,000	$ 8,604,000	$ 7,684,000
Federal Net Operating Loss carryforwards	0
State Net Operating Loss carryforwards	19,300,000
Federal foreign tax credits	2,400,000
Gross research credits	$ 3,628,000	484,000	$ 979,000
Cumulative changes in ownership percentage	50.00%
Cumulative changes in ownership period	3 years
Realized upon settlement	50.00%
Unrecognized tax benefits that would impact effective tax rate	$ (9,300,000)	(8,100,000)
Accrued interest and penalties associated with uncertain tax positions	300,000
Interest expense, net of accrued interest reversed	100,000	$ 100,000
Federal research credits [Member]
Income Taxes Disclosure [Line Items]
Federal research credits	5,800,000
Gross State Research Credits [Member]
Income Taxes Disclosure [Line Items]
Gross research credits	12,800,000
State research credit - no expiry	12,400,000
State research credit - with expiry	$ 400,000