Selected Quarterly Financial Data (unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								6 Months Ended	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2018	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Quarterly Financial Data [Abstract]
Revenues	$ 935.8	$ 928.4	$ 914.0	$ 905.0	$ 907.7	$ 852.4	$ 849.7	$ 879.1		$ 3,683.2		$ 3,488.9		$ 3,347.0
Operating Profit	73.3	52.5	52.6	58.4	81.2	67.0	61.7	64.8		236.8		274.7		273.9
Amounts attributable to Brink’s:
Continuing operations	(3.8)	5.8	12.6	13.7	34.9	17.5	(107.8)	22.1		28.3		(33.3)		16.9
Discontinued operations	1.2	(0.4)	(0.1)	0.0	0.0	(0.1)	(0.1)	0.2		0.7		0.0		(0.2)
Net income (loss) attributable to Brink’s	(2.6)	5.4	12.5	13.7	34.9	17.4	(107.9)	22.3		29.0		(33.3)		16.7
Depreciation and amortization	45.5	42.9	48.7	47.9	42.8	41.6	39.1	38.8		185.0		162.3		146.6
Capital expenditures	$ 48.8	$ 42.9	$ 37.9	$ 35.2	$ 51.1	$ 30.7	$ 36.6	$ 36.7		$ 164.8		$ 155.1		$ 174.5
Basic
Continuing operations (in dollars per share)	$ (0.08)	$ 0.11	$ 0.25	$ 0.27	$ 0.69	$ 0.34	$ (2.11)	$ 0.43		$ 0.56	[1]	$ (0.65)	[1]	$ 0.33	[1]
Discontinued operations (in dollars per share)	0.02	(0.01)	0	0	0	0	0	0		0.01	[1]	0	[1]	(0.01)	[1]
Net income (loss) (in dollars per share)	(0.05)	0.11	0.25	0.27	0.69	0.34	(2.11)	0.44		0.58	[1]	(0.65)	[1]	0.33	[1]
Diluted
Continuing operations (in dollars per share)	(0.08)	0.11	0.25	0.27	0.68	0.34	(2.11)	0.42		0.55	[1]	(0.65)	[1]	0.33	[1]
Discontinued operations (in dollars per share)	0.02	(0.01)	0	0	0	0	0	0		0.01	[1]	0	[1]	(0.01)	[1]
Net income (loss) (in dollars per share)	$ (0.05)	$ 0.10	$ 0.25	$ 0.27	$ 0.68	$ 0.34	$ (2.11)	$ 0.43		$ 0.57	[1]	$ (0.65)	[1]	$ 0.32	[1]
Effect of Fourth Quarter Events [Line Items]
Share-based expense for modification			$ 6.9							$ 42.7		$ 28.2		$ 17.7
Gain on lease termination			5.2							5.2
Revenues	$ 935.8	$ 928.4	$ 914.0	$ 905.0	$ 907.7	$ 852.4	$ 849.7	$ 879.1		3,683.2		3,488.9		3,347.0
Brazil social tax credit										0.3		0.6		0.4
Loss on deconsolidation of Venezuela operations										0.0		(126.7)		0.0
Foreign currency transaction losses										0.0		(15.5)		(7.6)
Gain on sale of business										0.0		11.2		0.0
Brazil
Quarterly Financial Data [Abstract]
Revenues										440.4		405.4		434.6
Effect of Fourth Quarter Events [Line Items]
Revenues										440.4		405.4		434.6
Brazil social tax credit	8.2
Venezuela
Quarterly Financial Data [Abstract]
Revenues										0.0		51.4		154.1
Effect of Fourth Quarter Events [Line Items]
Revenues										0.0		51.4		154.1
ARGENTINA
Quarterly Financial Data [Abstract]
Revenues										214.4		247.2		250.3
Effect of Fourth Quarter Events [Line Items]
Revenues										214.4		247.2		250.3
Venezuelan bolívar fuerte | Venezuela
Effect of Fourth Quarter Events [Line Items]
Loss on deconsolidation of Venezuela operations							126.7
Currency remeasurement gain (loss)									$ 2.2					(9.1)
Argentina, Pesos | ARGENTINA
Effect of Fourth Quarter Events [Line Items]
Foreign currency transaction losses							12.6
Currency remeasurement gain (loss)						$ (8.1)				(11.3)		(6.2)
French airport security services company
Effect of Fourth Quarter Events [Line Items]
Gain on sale of business							$ 11.2
Internal Loss AR Rebuild
Quarterly Financial Data [Abstract]
Revenues		4.0
Effect of Fourth Quarter Events [Line Items]
Revenues		4.0
Bank fees		0.3
Increase to bad debt expense	6.4	13.7								20.1
Immaterial error correction		$ 10.0
Pension plan
Effect of Fourth Quarter Events [Line Items]
Settlement charge										(21.4)		(1.7)		(2.0)
U.S. Plans
Effect of Fourth Quarter Events [Line Items]
Settlement charge										$ (19.3)		$ 0.0		$ 0.0
U.S. Plans | Pension plan
Effect of Fourth Quarter Events [Line Items]
Settlement charge	$ 19.3

[1] Amounts may not add due to rounding.