Basis of presentation (Details) $ in Millions		3 Months Ended
		Mar. 31, 2018 USD ($) segment $ / $ / $	Mar. 31, 2017 USD ($) / $	Dec. 31, 2017 USD ($) $ / $ / $	Dec. 31, 2016 $ / $ / $
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of operating segments | segment		3
Cash and cash equivalents		$ 562.2		$ 614.3
Accumulated other comprehensive losses related to Venezuela		916.6		926.6
Goodwill		444.7		$ 453.7
Cumulative effect of change in accounting principle	[1]	2.2
Net Cash Provided by Operating Activities		56.8	$ 39.4
Net Cash Provided by Financing Activities		(13.8)	52.8
Effect of exchange rate changes on cash		0.3	$ 6.9
Argentina
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Nonmonetary assets		$ 226.7
Percent of Consolidated Revenue		8.00%
Goodwill		$ 141.8
Equity Securities		$ 13.5
Venezuelan bolívar fuerte | Venezuela
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Rate decrease percent		93.00%	5.00%
Remeasurement rate | / $		49,478	710	3,345	674
Net remeasurement loss		$ (2.8)	$ 0.3
Income (loss) attributable to noncontrolling interest		2.0	0.1
Net monetary assets		1.0		$ 2.3
Cash and cash equivalents		0.5		3.4
Accumulated other comprehensive losses related to Venezuela		$ 114.6		$ 114.9
Argentine pesos | Argentina
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Rate decrease percent		8.00%		15.00%
Net monetary assets		$ (31.5)
Cash and cash equivalents		$ 27.4
Official exchange rate | $ / $		20.2		18.6	15.9
Venezuela Investment | Venezuelan bolívar fuerte | Venezuela
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Investment in Venezuela operations		$ 22.8		$ 23.1
Net payables to other Brink's affiliates		1.4		2.7
Nonmonetary assets		25.8		23.0
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			12.5
Net Cash Provided by Financing Activities			1.5
Effect of exchange rate changes on cash			$ 0.7

[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.