Goodwill and Other Intangible Assets - Summary of Intangible Assets Activity (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Cost amortizable intangible assets	$ 8.1	$ 8.1
Accumulated amortization intangible assets	5.0	4.2
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Cost amortizable intangible assets	4.9	4.9
Accumulated amortization intangible assets	2.2	1.8
Trademarks [Member]
Finite Lived Intangible Assets [Line Items]
Cost amortizable intangible assets	1.6	1.6
Accumulated amortization intangible assets	1.2	0.9
Other [Member]
Finite Lived Intangible Assets [Line Items]
Cost amortizable intangible assets	1.6	1.6
Accumulated amortization intangible assets	$ 1.6	$ 1.5