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, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Expense Benefit [Line Items]
Deferred tax impact of federal rate change			$ 7.4
Deferred tax impact of state tax rate change	$ 0.3	$ 0.1