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Provision for Income Taxes - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Income Tax Disclosure [Abstract]      
U.S. federal statutory income tax rate 21.00% 35.00% 35.00%
Non-cash deferred income tax benefit     $ 1.9