Related Party Transactions (Leases and Other Transactions) (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	2 Months Ended	3 Months Ended
	Feb. 28, 2018	Mar. 31, 2018	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2017
Management [Member] | 2017 Oil and Gas Acquisition [Member]
Related Party Transaction [Line Items]
Business combinations, cash paid (in dollars)				$ 40.6
Management [Member] | 2017 Oil and Gas Acquisition [Member] | Earn-Out Liabilities [Member]
Related Party Transaction [Line Items]
Business combinations, contingent consideration, liabilities (in dollars)		$ 59.9	$ 59.9
Management [Member] | Lease Agreements [Member]
Related Party Transaction [Line Items]
Payments, related party			7.5		$ 12.7
Payables, related party		3.4	3.4			$ 0.1
Management [Member] | Service Agreements [Member]
Related Party Transaction [Line Items]
Payments, related party			9.0		$ 6.6
Payables, related party		1.4	1.4			5.2
Management [Member] | Construction Contracts [Member]
Related Party Transaction [Line Items]
Revenue, related party			2.7
Receivables, related party		2.0	2.0			$ 0.6
Immediate Family Member of Management [Member] | Construction Management Firm Specializing in Steel Building Systems [Member]
Related Party Transaction [Line Items]
Business combinations, cash paid (in dollars)	$ 5.4
Business combinations, liabilities assumed, notes payable	$ 2.6
Repayments of notes payable		2.6
Immediate Family Member of Management [Member] | Construction Management Firm Specializing in Steel Building Systems [Member] | Earn-Out Liabilities [Member]
Related Party Transaction [Line Items]
Business combinations, contingent consideration, liabilities (in dollars)		$ 1.3	$ 1.3