XML 121 R106.htm IDEA: XBRL DOCUMENT v3.10.0.1
Income Taxes - Summary of Differences Between Total Income Tax Expense Statutory Federal Income Tax Rate (Parenthetical) (Detail) - TRS [Member] - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Income Tax Expense Benefit [Line Items]    
Deferred tax impact of federal rate change   $ 19.4
Deferred tax impact of state tax rate change $ 7.4