Income Tax - Reconciliation of Total Amounts of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Uncertainties [Abstract]
Balance, beginning of year	$ 12,219	$ 12,847	$ 19,859
Gross increases—tax positions in prior period	0	0	53
Gross decreases—tax positions in prior period	0	(345)	0
Lapse of statute of limitations	(3,071)	(283)	(7,065)
Balance, end of year	$ 9,148	$ 12,219	$ 12,847