Investments in Affiliated Companies (Summarized Financial Data-RRPF) (Details 6) $ in Millions		12 Months Ended
		Dec. 31, 2017 USD ($) AircraftEngines	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Schedule of Equity Method Investments [Line Items]
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment		$ 2,853.3	$ 2,641.7
Income Statement [Abstract]
Lease revenue		350.7	333.7	$ 339.3
Net income		100.4	99.3	121.4
Assets [Abstract]
Current assets		144.8	254.1
Other noncurrent assets		3,847.2	3,363.6
Total assets		3,992.0	3,617.7
Liabilities and Equity [Abstract]
Current liabilities		446.8	551.0
Long-term debt		2,704.9	2,341.4
Shareholders’ equity		840.3	725.3
Total liabilities and shareholders' equity		3,992.0	3,617.7
Rolls Royce Partners Finance [Member]
Income Statement [Abstract]
Income taxes			(7.8)	(15.4)
RRPF Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment		$ 943.5	1,007.4
Number of Aircraft Engines | AircraftEngines		432
Income Statement [Abstract]
Depreciation expense		$ (176.4)	(171.6)	(166.1)
Interest expense		(64.3)	(59.2)	(56.7)
Other expenses		(8.9)	(8.0)	(8.8)
Gains on sales of assets		20.5	19.1	33.1
Income before income taxes		115.7	104.2	131.6
Income taxes	[1]	(13.2)	(6.9)	(9.0)
Net income		102.5	97.3	122.6
Assets [Abstract]
Current assets		135.3	241.3
Operating assets, net of accumulated depreciation of $744.5 and $651.8	[2]	3,772.4	3,281.9
Total assets		3,907.7	3,523.2
Liabilities and Equity [Abstract]
Current liabilities		53.9	127.3
Long-term debt		2,751.1	2,452.9
Other liabilities		274.1	233.8
Shareholders’ equity		828.6	709.2
Total liabilities and shareholders' equity		3,907.7	3,523.2
RRPF Joint Ventures [Member] | Third Parties [Member]
Income Statement [Abstract]
Lease revenue		168.8	173.7	191.4
RRPF Joint Ventures [Member] | Rolls Royce [Member]
Income Statement [Abstract]
Lease revenue		$ 176.0	$ 150.2	$ 138.7

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