Income Taxes - Narrative (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Reduction in income tax expense due to Tax Cuts and Jobs Act of 2017	$ 9,168	$ 0	$ 0
Effective rate (as a percent)	22.70%
Unrecognized tax benefits recorded	$ 0	0
Amounts accrued for interest or penalties	$ 0	$ 0