Class A Redeemable Convertible Preferred Stock - Additional Information (Detail) - USD ($)		3 Months Ended	6 Months Ended	12 Months Ended
	Dec. 22, 2016	Jun. 30, 2017	Jun. 30, 2017	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 30, 2015
Temporary Equity [Line Items]
Temporary equity, shares issued		6,600,000	6,600,000			6,600,000
Temporary equity, face value		$ 0.001	$ 0.001			$ 0.001
Temporary equity, shares outstanding		6,600,000	6,600,000			6,600,000
Series A Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Temporary equity, shares issued							14,666,667
Temporary equity, face value							$ 7.50
Temporary equity, liquidation value		$ 49,500,000	$ 49,500,000				$ 110,000,000
Temporary equity, liquidation description			During the first year, the Series A Preferred Stock had a liquidation value of $100 million if the shares were redeemed prior to December 29, 2016.
Temporary equity, liquidation at redemption		100,000,000	$ 100,000,000
Temporary equity, shares redemption	8,066,667
Temporary equity, redemption amount	$ 55,000,000
Temporary equity, redemption per share	$ 6.8181825
Redemption Discount	9.0909%
Temporary equity, shares outstanding	6,600,000
Temporary equity, carrying amount		27,700,000	27,700,000			$ 22,900,000
Temporary equity, accrual of deemed dividends			1,800,000
Temporary equity, accretion of beneficial conversion feature			3,400,000
Temporary equity, fair value		$ 32,900,000	$ 32,900,000				$ 73,200,000
Temporary equity issued, price per share		$ 4.99	$ 4.99				$ 4.99
Temporary equity issue discount		$ 16,600,000	$ 16,600,000				$ 36,800,000
Temporary equity, value of beneficial conversion feature		20,100,000	20,100,000				$ 44,700,000
Temporary equity, recognized amount of beneficial conversion feature		1,700,000	3,400,000
Series A Redeemable Convertible Preferred Stock [Member] | Payment In Kind Period Two [Member]
Temporary Equity [Line Items]
Temporary equity, additional BCF discount		201,240	402,480
Temporary equity, fair value		$ 49,500,000	$ 49,500,000		$ 49,500,000
Series A Redeemable Convertible Preferred Stock [Member] | Payment In Kind Period Two [Member] | Scenario, Forecast [Member]
Temporary Equity [Line Items]
Temporary equity, face value				$ 7.50
Additional preferred stock to be issued				264,000
Payment-in-kind Dividend Rate per Annum in Effect				4.00%