Business Segments - Balance Sheet Items (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Accounts receivable, net:
Accounts receivable, net	$ 2,666.3	$ 2,705.6
Total assets:
Total assets	5,472.1	5,587.8
Aviation segment
Accounts receivable, net:
Accounts receivable, net	991.1	1,013.0
Allowance for bad debt	11.1	10.8
Land segment
Accounts receivable, net:
Accounts receivable, net	912.4	874.7
Allowance for bad debt	4.1	6.6
Marine segment
Accounts receivable, net:
Accounts receivable, net	762.7	817.9
Allowance for bad debt	9.4	10.4
Operating Segments | Aviation segment
Total assets:
Total assets	2,160.2	2,240.4
Operating Segments | Land segment
Total assets:
Total assets	2,144.3	2,091.4
Operating Segments | Marine segment
Total assets:
Total assets	986.5	1,097.1
Corporate
Total assets:
Total assets	$ 181.0	$ 158.9