Basis of presentation (Details) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2018 USD ($) $ / $ / $	Jun. 30, 2017 USD ($) / $	Jun. 30, 2018 USD ($) segment $ / $ / $	Jun. 30, 2017 USD ($) / $	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) $ / $ / $	Dec. 31, 2016 $ / $ / $
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of operating segments | segment				3
Loss on deconsolidation of Venezuela operations		$ (126.7)	$ 0.0	$ (126.7)	$ 0.0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Deconsolidation, pretax		(129.9)	$ (13.0)	(144.9)	(26.0)
Net monetary liabilities		2,625.3		2,625.3			$ 2,721.4
Cash and cash equivalents		548.5		548.5			614.3
Accumulated other comprehensive losses related to Venezuela		927.0		927.0			926.6
Net monetary assets		1,397.4		1,397.4			1,488.2
Goodwill		375.0		375.0			$ 453.7
Cumulative effect of change in accounting principle	[1]					$ 2.2
Net Cash Provided by Operating Activities				109.1	124.7
Net Cash Provided by Financing Activities				(54.5)	79.0
Effect of exchange rate changes on cash				(24.0)	$ (0.4)
Argentina
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Nonmonetary assets		181.5		$ 181.5
Percent of Consolidated Revenue				8.00%
Goodwill		98.6		$ 98.6
Equity Securities		34.4		$ 34.4
Venezuelan bolívar fuerte | Venezuela
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Loss on deconsolidation of Venezuela operations		127.0
Derecognition of the carrying amounts of assets included in the deconsolidation charge		32.0
Derecognition of the carrying amounts of liabilities included in the deconsolidation charge		$ 11.0
Rate decrease percent		97.00%	74.00%	97.00%	74.00%
Remeasurement rate | / $		115,000	2,640	115,000	2,640		3,345	674
Net remeasurement loss				$ (2.2)	$ 8.4
Income (loss) attributable to noncontrolling interest				$ 2.0	0.9
Net monetary liabilities							$ 2.3
Cash and cash equivalents							3.4
Accumulated other comprehensive losses related to Venezuela							$ 114.9
Argentine pesos | Argentina
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Rate decrease percent		36.00%		36.00%			15.00%
Cash and cash equivalents		$ 5.2		$ 5.2
Official exchange rate | $ / $		28.9		28.9			18.6	15.9
Net monetary assets		$ 18.2		$ 18.2
Venezuela Investment | Venezuelan bolívar fuerte | Venezuela
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Investment in Venezuela operations							$ 23.1
Net payables to other Brink's affiliates							2.7
Nonmonetary assets							23.0
Foreign currency translation adjustments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Deconsolidation, pretax		(107.2)	$ 0.0	$ (107.2)	0.0
Foreign currency translation adjustments | Venezuelan bolívar fuerte | Venezuela
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Deconsolidation, pretax		$ 106.0
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle	[1]					$ 3.3
Accounting Standards Update 2014-09 | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle							1.5
Accounting Standards Update 2016-01 | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle							1.1
Accounting Standards Update 2016-16 | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle							$ 0.7
Accounting Standards Update 2016-18
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by Operating Activities					23.4
Net Cash Provided by Financing Activities					1.8
Effect of exchange rate changes on cash					$ 7.0

[1] Effective January 1, 2018, we adopted the provisions of ASU 2014-09, Revenue From Contracts with Customers, ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities, and ASU 2016-16, Intra-Entity Transfers of Assets Other Than Inventory. We recognized a cumulative effect adjustment to January 1, 2018 retained earnings as a result of adopting each of these standards. See Note 1 for further details of the impact of each standard.