Investments in Affiliated Companies (Summarized Financial Data-RRPF) (Details 6) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment		$ 3,313.3				$ 3,066.2				$ 3,313.3	$ 3,066.2
Income Statement [Abstract]
Depreciation expense										(342.8)	(332.7)	$ (327.3)
Interest expense, net										(190.3)	(180.5)	(162.9)
Income Taxes										(37.3)	(40.9)	(30.5)
Net Income		17.8	$ 47.9	$ 39.3	$ 46.3	56.6	$ 45.1	$ 68.0	$ 41.5	151.3	211.2	211.3
Assets [Abstract]
Total Assets		8,937.6				8,285.1				8,937.6	8,285.1	7,318.9
EquityMethodInvestmentSummarizedFinancialInformationAPandAccruedExpense		147.3				119.4				147.3	119.4
Liabilities and Equity [Abstract]
Other liabilities		135.6				139.1				135.6	139.1
Total Liabilities and Shareholders’ Equity		8,937.6				8,285.1				8,937.6	8,285.1
Total Revenues		304.9	$ 304.4	$ 300.5	$ 299.4	300.5	$ 298.8	$ 297.5	$ 305.3	1,209.2	1,202.1	1,175.1
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Income Statement [Abstract]
Gains on sales of assets										115.7	86.4	12.2
Net Income										146.1	161.4	120.5
Assets [Abstract]
Total Assets		5,119.6				5,219.5				5,119.6	5,219.5
Liabilities and Equity [Abstract]
Current liabilities		311.0				525.5				311.0	525.5
Liabilities, Noncurrent		3,674.7				3,703.6				3,674.7	3,703.6
Total Liabilities and Shareholders’ Equity		5,119.6				5,219.5				5,119.6	5,219.5
Total Revenues										491.0	469.8	436.9
Current assets		352.7				203.6				352.7	203.6
RRPF Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment		1,283.6				1,178.5				1,283.6	1,178.5
RRPF Joint Ventures [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Income Statement [Abstract]
Depreciation expense										(248.7)	(223.9)	(195.6)
Interest expense, net										(116.0)	(126.4)	(94.3)
Other expenses										(50.3)	(16.5)	(12.6)
Gains on sales of assets										115.7	86.4	12.5
Income Taxes										(45.6)	(27.9)	(18.1)
Net Income										146.1	161.7	103.2
Assets [Abstract]
Total Assets		5,119.6				5,218.5				5,119.6	5,218.5
EquityMethodInvestmentSummarizedFinancialInformationAPandAccruedExpense		110.4				96.2				110.4	96.2
Liabilities and Equity [Abstract]
Current liabilities		200.6				429.3				200.6	429.3
Liabilities, Noncurrent		3,243.6				3,367.5				3,243.6	3,367.5
Other liabilities		431.1				336.1				431.1	336.1
Shareholders’ equity		1,133.9				989.4				1,133.9	989.4
Total Liabilities and Shareholders’ Equity		5,119.6				5,218.5				5,119.6	5,218.5
Net Assets	[1]	4,766.9				5,015.9				4,766.9	5,015.9
Current assets		$ 352.7				$ 202.6				352.7	202.6
Income (Loss) Attributable to Parent, before Tax										191.7	189.6	121.3
RRPF Joint Ventures [Member] | Third Parties [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Liabilities and Equity [Abstract]
Total Revenues										257.6	213.3	178.6
RRPF Joint Ventures [Member] | Rolls Royce [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Liabilities and Equity [Abstract]
Total Revenues										$ 233.4	$ 256.7	$ 232.7

[1] (a) All operating assets were pledged as collateral for long-term debt obligations.