Annual report pursuant to Section 13 and 15(d)

Income Taxes - Variations from Federal Statutory Rate (Parenthetical) (Detail)

v3.8.0.1
Income Taxes - Variations from Federal Statutory Rate (Parenthetical) (Detail)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Income Tax Disclosure [Abstract]      
Expected federal income tax expense (benefit), statutory rate 34.00% 34.00% 34.00%