Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Effective Income Tax rate Reconciliation, Percent	(20.40%)	5.30%
Valuation Allowances and Reserves, Deductions	$ 1.0
Valuation allowance, deferred tax asset, change in amount		$ 35.2
Federal corporate tax	21.00%		35.00%

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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-Name Accounting Standards Codification
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-SubTopic 10
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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
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Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

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Amount of decrease in valuation and qualifying accounts and reserves.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
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