Income Taxes - Reconciliation of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 46,591	$ 46,004
Additions based on tax positions related to the current year	4,440	3,897
Reductions for tax positions of prior years	(4,921)	(3,310)
Settlements	0	0
Balance at end of year	$ 46,110	$ 46,591