Legal Proceedings -Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions			1 Months Ended		3 Months Ended	6 Months Ended		12 Months Ended
	Jan. 29, 2018	Mar. 29, 2016	Feb. 28, 2018	Dec. 31, 2017	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2015	Jun. 29, 2018
Loss Contingencies [Line Items]
Attorney fees cost and expenses	$ 15,000
Reserve for settlement of fines				$ 17,073	$ 1,406	$ 1,406		$ 17,073	$ 4,000
Estimated insurance recoveries				$ 15,000				15,000
Non-cash charge for Settlement warrants						(9,660)	$ 24,409	$ 2,100
Reversal of cash settlement from contingent liability										$ 15,000
Litigation settlement amount paid by company		$ 4,000
Settlement fees					(709)	(667)			$ 4,000
Settlement Warrants
Loss Contingencies [Line Items]
Warrants to purchase of common stock shares	2.0
Warrants exercisable period	1 year			1 year
Warrants exercise price				$ 3.00				$ 3.00
Cash settlement from insurance carriers			$ 15,000
Reserve for settlement of fines				$ 17,100				$ 17,100
Estimated insurance recoveries				$ 15,000	15,000	15,000		$ 15,000
Non-cash charge for Settlement warrants					$ (700)	$ (700)