Related Party Transactions (Executive Officers) (Narrative) (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($) employee	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Management [Member] \| Subcontracting Arrangements [Member]
Related Party Transaction [Line Items]
Number of additional management employees, subcontracting arrangement \| employee	2
Payments or amounts incurred, related party	$ 10.3	$ 9.9	$ 78.0
Payables, related party	0.2	0.4
Executive Officers [Member] \| Related Customer [Member]
Related Party Transaction [Line Items]
Receivables, related party	0.8	0.6
Charges, related party	1.4	1.7	1.6
Executive Officers [Member] \| Construction Services [Member]
Related Party Transaction [Line Items]
Revenue, related party	12.6
Receivables, related party	3.9
Chairman, Board of Directors [Member] \| Leases [Member]
Related Party Transaction [Line Items]
Payments or amounts incurred, related party	$ 2.4	$ 2.7	$ 2.0

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