Goodwill and Other Intangible Assets - Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Intangible assets subject to amortization:
Intangible assets, Gross Carrying Amount	$ 733.7	$ 575.8
Intangible assets, Accumulated Amortization	373.8	332.9
Intangible assets, Net Carrying Amount	359.9	242.9
Indefinite Lived Intangible Assets Net	60.7	28.1
Total intangible assets, Net Carrying Amount	420.6	271.0
Intangible Assets, Gross (Excluding Goodwill)	794.4	603.9
Customer Relationships [Member]
Intangible assets subject to amortization:
Intangible assets, Gross Carrying Amount	324.6	211.4
Intangible assets, Accumulated Amortization	103.0	84.4
Intangible assets, Net Carrying Amount	221.6	127.0
Technology-Based Intangible Assets [Member]
Intangible assets subject to amortization:
Intangible assets, Gross Carrying Amount	128.7	95.2
Intangible assets, Accumulated Amortization	33.8	25.4
Intangible assets, Net Carrying Amount	94.9	69.8
Unclassified Indefinite-lived Intangible Assets [Member]
Intangible assets subject to amortization:
Intangible assets, Gross Carrying Amount	10.3	11.0
Intangible assets, Accumulated Amortization	6.2	7.5
Intangible assets, Net Carrying Amount	4.1	3.5
Trademarks [Member]
Intangible assets subject to amortization:
Intangible assets, Gross Carrying Amount	8.6	6.5
Intangible assets, Accumulated Amortization	4.3	3.8
Intangible assets, Net Carrying Amount	4.3	2.7
Software and Software Development Costs [Member]
Intangible assets subject to amortization:
Intangible assets, Gross Carrying Amount	261.5	251.7
Intangible assets, Accumulated Amortization	226.5	211.8
Intangible assets, Net Carrying Amount	35.0	39.9
Trade Names [Member]
Intangible assets subject to amortization:
Intangible assets, Accumulated Amortization
Tradename	52.0	19.4
FAA air agency certificates [Member]
Intangible assets subject to amortization:
Intangible assets, Accumulated Amortization
Indefinite Lived FAA Air Agency Certificates	$ 8.7	$ 8.7