Income Taxes - Information of UTPs Affecting Effective Tax Rate, if Recognized (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning Balance	$ 1,300,000	$ 2,300,000	$ 2,200,000
Current year additions	600,000	100,000	100,000
Current year reduction due to lapse of applicable statute of limitations		(1,100,000)	0
Current year reduction due to audit settlement	400,000
Ending Balance	$ 1,500,000	$ 1,300,000	$ 2,300,000