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Amount for accounts payable to related parties.

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Related Party Transactions (Executive Officers) (Narrative) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) employee	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) employee	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Management [Member] \| Subcontracting Arrangements [Member] \| Related Contractor or Supplier [Member]
Related Party Transaction [Line Items]
Number of additional management employees, subcontracting arrangement \| employee	2		2
Payments or expenses, related party	$ 1.1	$ 39.2	$ 7.8	$ 54.8
Payables, related party	1.9		1.9		$ 2.0
Management [Member] \| Service Agreements [Member]
Related Party Transaction [Line Items]
Payments or expenses, related party	22.4	26.4	35.8	41.0
Payables, related party	37.9		37.9		5.2
Management [Member] \| Lease Agreements [Member]
Related Party Transaction [Line Items]
Payments or expenses, related party	11.8	11.3	30.1	38.4
Payables, related party	4.7		4.7		0.1
Executive Officers [Member] \| Employee Leasing Arrangements [Member] \| Related Customer [Member]
Related Party Transaction [Line Items]
Charges, related party	0.2	0.2	0.6	0.6
Receivables, related party	0.3		0.3		0.2
Executive Officers [Member] \| Service Agreements [Member] \| Related Customer [Member]
Related Party Transaction [Line Items]
Revenue, related parties	0.2	0.2	0.7	0.6
Receivables, related party	0.3		0.3		$ 0.3
Chairman, Board of Directors [Member] \| Lease Agreements [Member] \| Aircraft [Member]
Related Party Transaction [Line Items]
Payments or expenses, related party	$ 0.9	$ 0.5	$ 2.0	$ 1.5