Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Federal net operating loss carryforward expiration year	2033
State net operating loss carryforward expiration year	2020
Valuation allowance related to tax law changes		$ 2.3
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
State NOL carryforwards		$ 3.4
Alternative minimum tax (ATM) remaining federal tax NOL carryforwards	$ 794.4
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Gross tax credits	$ 8.1
Tax carryforward period	20 years
Tax credit carryforward expiration year	2034
Alternative minimum tax (ATM) remaining federal tax NOL carryforwards	$ 629.3