Segment Reporting (Capital Expenditures by Reportable Segment) (Details) - USD ($) $ in Millions	3 Months Ended
Apr. 30, 2020	Apr. 30, 2019
Property, Plant and Equipment [Line Items]
Capital expenditures	$ 4.8	$ 29.6
Southwest
Property, Plant and Equipment [Line Items]
Capital expenditures	1.5	5.4
Rocky Mountains
Property, Plant and Equipment [Line Items]
Capital expenditures	2.2	11.5
Northeast/Mid-Con
Property, Plant and Equipment [Line Items]
Capital expenditures	$ 1.1	$ 12.7

The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3213-108585

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration