Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill impairment	$ 0.0	$ 0.0	$ 0.0
Amortization expense				$ 0.1	$ 0.1	$ 0.1
Expected amortization expense, 2016	0.1			0.1
Expected amortization expense, 2017	0.1			0.1
Expected amortization expense, 2018	0.1			0.1
Expected amortization expense, 2019	0.1			0.1
Expected amortization expense, 2020	$ 0.1			$ 0.1