Goodwill and Other Intangible Assets - Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Intangible assets subject to amortization:
Intangible assets, Gross Carrying Amount	$ 1,072.8		$ 1,045.0
Intangible assets, Accumulated Amortization	(444.5)		(416.7)
Intangible assets, Net Carrying Amount	628.3		628.3
Tradename	121.5		96.2
Indefinite Lived FAA Air Agency Certificates	8.7		8.7
Indefinite Lived Intangible Assets Net	130.2		104.9
Total intangible assets, Net Carrying Amount	758.5	$ 733.9	733.2
Intangible Assets, Gross (Excluding Goodwill)	1,203.0		1,149.9
Customer Relationships [Member]
Intangible assets subject to amortization:
Intangible assets, Gross Carrying Amount	510.9		481.5
Intangible assets, Accumulated Amortization	(128.8)		(99.8)
Intangible assets, Net Carrying Amount	382.1		381.7
Technology-Based Intangible Assets [Member]
Intangible assets subject to amortization:
Intangible assets, Gross Carrying Amount	265.1		245.0
Intangible assets, Accumulated Amortization	(54.7)		(40.4)
Intangible assets, Net Carrying Amount	210.4		204.6
Unclassified Indefinite-lived Intangible Assets [Member]
Intangible assets subject to amortization:
Intangible assets, Gross Carrying Amount	13.8		40.8
Intangible assets, Accumulated Amortization	(9.1)		(35.2)
Intangible assets, Net Carrying Amount	4.7		5.6
Trademarks [Member]
Intangible assets subject to amortization:
Intangible assets, Gross Carrying Amount	12.7		11.3
Intangible assets, Accumulated Amortization	(6.1)		(4.8)
Intangible assets, Net Carrying Amount	6.6		6.5
Software and Software Development Costs [Member]
Intangible assets subject to amortization:
Intangible assets, Gross Carrying Amount	270.3		266.4
Intangible assets, Accumulated Amortization	(245.8)		(236.5)
Intangible assets, Net Carrying Amount	24.5		29.9
Trade Names [Member]
Intangible assets subject to amortization:
Tradename	121.5		96.2
FAA air agency certificates [Member]
Intangible assets subject to amortization:
Indefinite Lived FAA Air Agency Certificates	$ 8.7		$ 8.7