Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net income attributable to World Fuel	$ 28.7	$ 30.0	$ 59.9	$ 61.4
Denominator:
Weighted average common shares for basic earnings per common share (in shares)	67.7	68.4	67.6	68.5
Effect of dilutive securities (in shares)	0.3	0.3	0.4	0.4
Weighted average common shares for diluted earnings per common share (in shares)	68.0	68.7	67.9	68.9
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)	1.2	1.9	1.4	1.3
Basic earnings per common share (in dollars per share)	$ 0.42	$ 0.44	$ 0.89	$ 0.90
Diluted earnings per common share (in dollars per share)	$ 0.42	$ 0.44	$ 0.88	$ 0.89