Revenue from contracts with customers Revenue from contracts with customers - comparative periods (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ 849.7	$ 805.9	$ 1,728.8	$ 1,594.3
Operating Profit	61.7	48.3	126.5	119.2
Reported net income (loss) attributable to Brink's	(107.9)	$ 14.2	(85.6)	$ 48.9
Prepaid expenses and other	151.6		151.6		$ 119.0
Other assets	166.4		166.4		144.9
Retained earnings	467.4		467.4		$ 564.9
Pro Forma under Old Revenue Recognition Standard
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	850.0		1,726.1
Operating Profit	62.4		126.1
Reported net income (loss) attributable to Brink's	(107.5)		(85.8)
Prepaid expenses and other	150.8		150.8
Other assets	164.8		164.8
Retained earnings	465.7		465.7
Accounting Standards Update 2014-09 | Impact of New Revenue Recognition Standard
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	(0.3)		2.7
Operating Profit	(0.7)		0.4
Reported net income (loss) attributable to Brink's	(0.4)		0.2
Prepaid expenses and other	0.8		0.8
Other assets	1.6		1.6
Retained earnings	$ 1.7		$ 1.7