Revenue from contracts with customers Revenue from contracts with customers - comparative periods (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ 852.4	$ 849.5	$ 2,581.2	$ 2,443.8
Operating Profit	67.0	66.4	193.5	185.6
Reported net income (loss) attributable to Brink's	17.4	$ 19.9	(68.2)	$ 68.8
Prepaid expenses and other	136.6		136.6		$ 119.0
Other assets	179.8		179.8		144.9
Retained earnings	456.7		456.7		$ 564.9
Pro Forma under Old Revenue Recognition Standard
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	850.3		2,576.4
Operating Profit	64.7		190.8
Reported net income (loss) attributable to Brink's	15.8		(70.0)
Prepaid expenses and other	134.1		134.1
Other assets	178.1		178.1
Retained earnings	453.4		453.4
Accounting Standards Update 2014-09 | Impact of New Revenue Recognition Standard
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	2.1		4.8
Operating Profit	2.3		2.7
Reported net income (loss) attributable to Brink's	1.6		1.8
Prepaid expenses and other	2.5		2.5
Other assets	1.7		1.7
Retained earnings	$ 3.3		$ 3.3