Basis of Presentation, New Accounting Standards and Significant Accounting Policies - Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	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
Numerator:
Net income (loss) attributable to World Fuel									$ 178.9	$ 127.7	$ (170.2)
Denominator:
Weighted average common shares for basic earnings per common share (in shares)									66.1	67.4	68.1
Effect of dilutive securities (in shares)									0.4	0.3	0.0
Weighted average common shares for diluted earnings per common share (in shares)									66.5	67.7	68.1
Weighted average securities which are not included in the calculation of diluted earnings per common share because their impact is anti-dilutive or their performance conditions have not been met (in shares)									1.4	1.2	1.4
Basic earnings (loss) per common share (in dollars per share)	$ 0.86	$ 0.74	$ 0.56	$ 0.55	$ 0.44	$ 0.57	$ 0.42	$ 0.46	$ 2.71	$ 1.89	$ (2.50)
Diluted earnings (loss) 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)