Goodwill and Other Intangible Assets - Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Intangible assets subject to amortization:
Intangible assets, gross carrying amount	$ 1,104.7	$ 1,072.8
Intangible assets, accumulated amortization	(501.0)	(444.5)
Intangible assets, net carrying amount	603.7	628.3
Trade names	129.0	121.5
Net indefinite lived intangible assets	137.7	130.2
Gross intangible assets (excluding goodwill)	1,242.4	1,203.0
Total intangible assets, net carrying amount	741.4	758.5
FAA air agency certificates
Intangible assets subject to amortization:
Net indefinite lived intangible assets	8.7	8.7
Customer relationships
Intangible assets subject to amortization:
Intangible assets, gross carrying amount	532.2	510.9
Intangible assets, accumulated amortization	(161.9)	(128.8)
Intangible assets, net carrying amount	370.3	382.1
Technology and know-how
Intangible assets subject to amortization:
Intangible assets, gross carrying amount	277.2	265.1
Intangible assets, accumulated amortization	(72.0)	(54.7)
Intangible assets, net carrying amount	205.2	210.4
Trade names
Intangible assets subject to amortization:
Intangible assets, gross carrying amount	14.2	12.7
Intangible assets, accumulated amortization	(8.8)	(6.1)
Intangible assets, net carrying amount	5.4	6.6
Trade names	129.0	121.5
Capitalized Software
Intangible assets subject to amortization:
Intangible assets, gross carrying amount	276.4	270.3
Intangible assets, accumulated amortization	(254.6)	(245.8)
Intangible assets, net carrying amount	21.8	24.5
Other
Intangible assets subject to amortization:
Intangible assets, gross carrying amount	4.7	13.8
Intangible assets, accumulated amortization	(3.7)	(9.1)
Intangible assets, net carrying amount	$ 1.0	$ 4.7