Income Taxes - Summary of Reconciliation of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Balance at January 1,				$ 124	$ 77	$ 3,847
Additions based on tax positions related to the current year				118	51	37
Additions based on tax positions related to prior years				537
Reductions due to statute of limitations expiring	$ (2)	$ (4)	$ (3,800)	(2)	(4)	(3,807)
Balance at December 31,				$ 777	$ 124	$ 77