Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Deferred tax assets, change in federal tax rate	$ 7.4		$ 7.4
Net operating losses carryback period			2 years
Capital losses carryback period			3 years
Change in valuation allowance	0.8	$ 1.2	$ (1.1)	$ 1.2
Unrecognized tax benefits, period increase (decrease)	(0.4)		(2.3)
Interest on income taxes expense	0.1		(0.3)
Tax penalty expense	$ 0.0		$ (0.4)