Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
Dec. 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Unrecognized tax benefits		$ 0
U.S. federal income tax statutory rate	21.00%	21.00%		35.00%
Company recognized uncertain tax positions		$ 0	$ 0

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

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Amount of increase (decrease) to previously recorded tax expense. Includes, but is not limited to, significant settlements of income tax disputes, and unusual tax positions or infrequent actions taken by the entity, including tax assessment reversal, and IRS tax settlement.

+ References

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Amount of increase (decrease) in unrecognized tax benefits attributable to uncertain tax positions taken in tax returns.

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