The amount of total capital as defined in the regulations.

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Fair Value Measurement - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions			12 Months Ended
	Jan. 05, 2018	Jan. 05, 2015	Dec. 31, 2017	Jun. 30, 2018	Jun. 15, 2018	Dec. 07, 2017
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Conversion price of common stock	$ 1.35
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]
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
Preferred stock liquidation preference per share		$ 1,000			$ 1,000
Preferred stock dividend rate calculated on interest rate		3.00%
Percentage of dividend payable in common stock accrued	5.00%
Conversion ceiling price of common stock				$ 2.25
Conversion floor price of common stock				1.75		$ 1.75
Conversion price of common stock	$ 1.35
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