Investments in Affiliated Companies (Future Debt Maturities) (Details 8) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
2016	$ 250.0	$ 250.0
2017	350.0	350.0
2018	663.1	663.1
2019	250.0	250.0
2020	250.0	250.0
Thereafter	2,710.0	2,710.0
Total debt principal	$ 4,473.1	$ 4,473.1	$ 4,412.6
RRPF Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Long-term Debt, Contingent Payment of Principal or Interest	369.0	259.0
2016	$ 732.1	$ 732.1
2017	420.3	420.3
2018	286.0	286.0
2019	425.6	425.6
2020	274.6	274.6
Thereafter	1,330.7	1,330.7
Total debt principal	$ 3,469.3	$ 3,469.3

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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