Acquisitions - Purchase Price Allocation to Other Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill, acquisition	$ 8.7	$ 7.0
Amount of goodwill deductible for tax purposes	69.4	70.0
South Segment
Business Acquisition [Line Items]
Goodwill, acquisition	4.6
East Segment
Business Acquisition [Line Items]
Goodwill, acquisition	0.0
Midwest Segment
Business Acquisition [Line Items]
Goodwill, acquisition	4.1
Business Acquisition
Business Acquisition [Line Items]
Other intangible assets	7.5	7.7
Amount of goodwill deductible for tax purposes	8.7	7.0
Business Acquisition | Customer lists and contracts
Business Acquisition [Line Items]
Other intangible assets	7.0	7.2
Business Acquisition | Noncompete
Business Acquisition [Line Items]
Other intangible assets	$ 0.5	$ 0.5