Income Taxation - Additional Information (Detail) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Bermuda income taxes, statutory rate	0.00%	0.00%	0.00%
Valuation allowance	$ 117,390,000	$ 212,113,000
Increase (decrease) in valuation allowance	(94,700,000)		$ (7,400,000)
Utilized deferred tax asset	69,700,000
Deferred tax asset valuation allowance release	25,000,000.0
Unrecognized tax benefits	0	0	0
Accrued interest and penalties related to unrecognized tax benefits	$ 0	$ 0	0
Decrease in deferred tax assets			$ 63,800,000

Valuation Allowance, Deferred Tax Asset, Utilized

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- Definition

Valuation Allowance, Deferred Tax Asset, Released

+ References

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

+ References

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to increase (decrease) in the valuation allowance for deferred tax assets.

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Amount of unrecognized tax benefits.

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Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

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