Fair Value Measurement - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions			12 Months Ended
	Jan. 05, 2018	Jan. 05, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 07, 2017	Dec. 31, 2015
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Expected volatility rate			60.00%	40.00%
Risk free interest rate			1.60%	0.60%
Expected probability of occurrence			95.00%	90.00%
Mandatory conversion, expected term			9 months	6 months
Variance from fair value of derivative			$ 28.2
Fair market value of derivative liability transferred to equity			$ 108.9
Subsequent Event [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Conversion price of common stock	$ 1.35
Redeemable Convertible Series B Preferred Stock [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Capital		$ 600.0
Redeemable Convertible preferred stock, shares issued		600,000	600,000	600,000		600,000
Preferred stock liquidation preference per share		$ 1,000
Preferred stock dividend rate calculated on interest rate		3.00%
Conversion ceiling price of common stock			$ 2.25		$ 2.25
Conversion floor price of common stock			$ 1.75		$ 1.75
Variance from fair value of derivative			$ 28.2
Fair market value of derivative liability transferred to equity			$ 108.9
Redeemable Convertible Series B Preferred Stock [Member] | Maximum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Conversion ceiling price of common stock			$ 2.25
Redeemable Convertible Series B Preferred Stock [Member] | Subsequent Event [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Percentage of dividend payable in common stock accrued	5.00%
Conversion price of common stock	$ 1.35