Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Effective income tax rate (as a percent)	15.70%	28.50%	23.40%	29.70%
Favorable deferred tax adjustment	$ 9.5
Liability for uncertain tax positions	5.7		$ 5.7
Unrecognized tax benefits if recognized that would affect effective tax rate	3.2		3.2
Accrued interest related to uncertain tax positions	0.6		0.6		$ 0.8
Accrued penalties related to uncertain tax positions	0.3		0.3		$ 0.3
Unrecognized tax benefits subject to change within the next 12 months	$ 3.6		$ 3.6