Disclosure - Goodwill and Other Intangible Assets - Summary of Intangible Assets Activity (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Finite Lived Intangible Assets [Line Items]
Cost amortizable intangible assets	$ 8.1	$ 1.4
Accumulated amortization intangible assets	1.7	0.9
Customer relationships [Member]
Finite Lived Intangible Assets [Line Items]
Cost amortizable intangible assets	4.9	1.4
Accumulated amortization intangible assets	1.1	0.9
Trademarks [Member]
Finite Lived Intangible Assets [Line Items]
Cost amortizable intangible assets	1.6	0.0
Accumulated amortization intangible assets	0.2	0.0
Other [Member]
Finite Lived Intangible Assets [Line Items]
Cost amortizable intangible assets	1.6	0.0
Accumulated amortization intangible assets	$ 0.4	$ 0.0