Income Taxes - Summary of Unrecognized Tax Benefits and the Associated Interest and Penalties (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Unrecognized Tax Benefits
Beginning balance, Unrecognized tax benefits	$ 493,000	$ 482,000
Deferred tax position	11,000	11,000
Ending balance, Unrecognized tax benefits	504,000	493,000
Interest and Penalties
Beginning balance, Interest and penalties	0	0
Deferred tax position	0	0
Ending balance at December, Interest and penalties	$ 0	$ 0