Revenue from contracts with customers Revenue from contracts with customers - comparative periods (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ 907.7	$ 852.4	$ 849.7	$ 879.1	$ 903.2	$ 849.5	$ 805.9	$ 788.4	$ 3,488.9	$ 3,347.0	$ 3,020.6
Operating Profit	81.2	67.0	61.7	64.8	88.3	66.4	48.3	70.9	274.7	273.9	184.5
Reported net income (loss) attributable to Brink's	34.9	$ 17.4	$ (107.9)	$ 22.3	(52.1)	$ 19.9	$ 14.2	$ 34.7	(33.3)	16.7	$ 34.5
Prepaid Expense and Other Assets	127.5								127.5
Other assets	186.1				144.9				186.1	144.9
Retained earnings	429.1				$ 564.9				429.1	$ 564.9
Impact of New Revenue Recognition Standard | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues									4.0
Operating Profit									2.0
Reported net income (loss) attributable to Brink's									1.4
Prepaid Expense and Other Assets	1.8								1.8
Other assets	1.8								1.8
Retained earnings	2.9								2.9
Pro Forma under Old Revenue Recognition Standard
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues									3,484.9
Operating Profit									272.7
Reported net income (loss) attributable to Brink's									(34.7)
Prepaid Expense and Other Assets	125.7								125.7
Other assets	184.3								184.3
Retained earnings	$ 426.2								$ 426.2