Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Net deferred income tax assets	$ 47.2			$ 47.2		$ 48.0
Reduction in valuation allowance		$ 0.8
Effective tax rate increased	5.70%			6.50%
Decrease in effective tax rate	2.40%		2.70%	4.80%	5.20%
Decrease in unrecognized tax positions	$ 1.6			$ 1.6
Interest and penalties	$ 1.8			$ 1.8