Income Taxes - Changes in Unrecognized Tax Benefits Excluding Interest and Penalties (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Balance at January 1	$ 178	$ 794	$ 608
Additions for tax positions of prior years	0	0	186
Reductions for tax positions of prior years	0	(616)	0
Expiration of statutes of limitations	(178)	0	0
Balance at December 31	$ 0	$ 178	$ 794