Goodwill - Schedule of Changes in Carrying Amounts of Goodwill (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Goodwill [Line Items]
Goodwill	$ 586.1	$ 586.1
Accumulated impairment losses	(59.5)	(59.5)
Total	526.6	526.6
Commercial
Goodwill [Line Items]
Goodwill	377.1	377.1
Accumulated impairment losses	0.0	0.0
Total	377.1	377.1
Aviation
Goodwill [Line Items]
Goodwill	209.0	209.0
Accumulated impairment losses	(59.5)	(59.5)
Total	$ 149.5	$ 149.5