Related Party Transactions (Construction Management Firm and CCI) (Narrative) (Details) - Immediate Family Member of Management [Member] - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Construction Management Firm Specializing in Steel Building Systems [Member]
Related Party Transaction [Line Items]
Payments to acquire businesses, gross			$ 6.1
Business combinations, contingent consideration, earn-out liabilities			1.4
Advances outstanding, related party	$ 0.1	$ 0.5
CCI [Member] \| Equipment [Member]
Related Party Transaction [Line Items]
Payments, net of rebates, related party	6.8	41.7	$ 57.6
Payables, related party	4.2	$ 0.2
Revenue, related party	$ 0.9

Amount for accounts payable to related parties.

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