Revenue from contracts with customers Revenue from contracts with customers - comparative periods (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ 879.1	$ 788.4
Operating Profit	64.8	70.9
Reported net income attributable to Brink's	22.3	$ 34.7
Prepaid expenses and other	151.8		$ 119.0
Other assets	155.4		144.9
Retained earnings	582.9		$ 564.9
Pro Forma under Old Revenue Recognition Standard
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	876.1
Operating Profit	63.8
Reported net income attributable to Brink's	21.7
Prepaid expenses and other	150.3
Other assets	153.7
Retained earnings	580.8
Accounting Standards Update 2014-09 | Impact of New Revenue Recognition Standard
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	3.0
Operating Profit	1.0
Reported net income attributable to Brink's	0.6
Prepaid expenses and other	1.5
Other assets	1.7
Retained earnings	$ 2.1