Business Segments - Balance Sheet Items (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Accounts receivable, net:
Accounts receivable, net	$ 2,951.9	$ 2,705.6
Total assets:
Total assets	5,757.0	5,587.8
Aviation segment
Accounts receivable, net:
Accounts receivable, net	1,149.7	1,013.0
Allowance for bad debt	11.5	10.8
Land segment
Accounts receivable, net:
Accounts receivable, net	882.4	874.7
Allowance for bad debt	4.1	6.6
Marine segment
Accounts receivable, net:
Accounts receivable, net	919.7	817.9
Allowance for bad debt	9.8	10.4
Operating Segments | Aviation segment
Total assets:
Total assets	2,326.8	2,240.4
Operating Segments | Land segment
Total assets:
Total assets	2,107.2	2,091.4
Operating Segments | Marine segment
Total assets:
Total assets	1,159.9	1,097.1
Corporate
Total assets:
Total assets	$ 163.1	$ 158.9