Basis of Presentation, New Accounting Standards and Significant Accounting Policies - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended		3 Months Ended								12 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income (loss) attributable to World Fuel			$ 56.5	$ 48.2	$ 37.0	$ 37.2	$ 29.6	$ 38.2	$ 28.7	$ 31.2	$ 178.9	$ 127.7	$ (170.2)
Diluted earnings per common share (in dollars per share)			$ 0.86	$ 0.73	$ 0.55	$ 0.55	$ 0.44	$ 0.56	$ 0.42	$ 0.46	$ 2.69	$ 1.89	$ (2.50)
Income from operations											$ 299.7	$ 259.7	$ 45.6
Other investments			$ 85.1				$ 73.7				85.1	$ 73.7
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right of use assets														$ 167.3
Lease liabilities														$ 173.6
Recognized From Prior Period
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income from operations		$ 3.4
Income from operations, net of tax		2.3
Pro Forma
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income (loss) attributable to World Fuel											$ 169.9
Diluted earnings per common share (in dollars per share)											$ 2.56
Discrete tax benefit, prior year foreign tax return	$ 3.5	$ 3.2									$ 6.6