Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 15.4	$ 2.8
Benefit plan adjustments:
Benefit plan actuarial gains (losses)	(0.2)	18.6
Benefit plan prior service costs	(1.3)	(1.1)
Total benefit plan adjustments	(1.5)	17.5
Foreign currency translation adjustments	(46.0)	(120.3)
Gains (losses) on cash flow hedges	7.2	(14.7)
Other comprehensive loss before tax	(40.3)	(117.5)
Provision (benefit) for income taxes	2.5	(0.1)
Other comprehensive loss	(42.8)	(117.4)
Comprehensive loss	(27.4)	(114.6)
Less comprehensive income attributable to noncontrolling interests	0.6	0.6
Comprehensive loss attributable to Brink's	$ (28.0)	$ (115.2)