Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Income Tax Disclosure [Line Items]
Effective tax rate	10.30%	26.30%
Income tax rate at federal statutory rates	21.00%	21.00%
Federal Tax Credit Carry Forwards [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets, valuation allowance	$ 24.5		$ 39.5
State Tax Credit Carry Forwards [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets, valuation allowance	12.9		15.0
Federal Tax [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets, valuation allowance	7.3		7.1
Charitable Institution [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets, valuation allowance	$ 4.6		$ 4.0