Quarterly report pursuant to Section 13 or 15(d)

Income Taxes - Additional Information (Detail)

v3.10.0.1
Income Taxes - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Income Tax Disclosure [Abstract]          
Provision for income taxes, rate 28.50% 39.30% 27.20% 39.00%  
Tax computed at federal rate, percentage 21.00% 35.00% 21.00% 35.00% 35.00%
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Provisional Income Tax Expense         $ 11.6