Annual report pursuant to Section 13 and 15(d)

Income Taxes - Reconciliation of Tax Computed at the Statutory Federal Rate (Parenthetical) (Detail)

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Income Taxes - Reconciliation of Tax Computed at the Statutory Federal Rate (Parenthetical) (Detail)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Income Tax Disclosure [Abstract]    
Income tax benefit computed at statutory federal rate 21.00% 34.00%