Annual report pursuant to Section 13 and 15(d)

Income Taxes - Summary of Reconciliation of Statutory Tax Expense to Actual Tax Expense (Parenthetical) (Detail)

v3.8.0.1
Income Taxes - Summary of Reconciliation of Statutory Tax Expense to Actual Tax Expense (Parenthetical) (Detail)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Effective Income Tax Rate Reconciliation, Amount [Abstract]      
Federal statutory rate 34.00% 34.00% 34.00%