Consolidated Statement of Equity - USD ($) shares in Millions, $ in Millions		Total	Cumulative Effect, Period of Adoption, Adjustment		Common Stock	Capital in Excess of Par Value	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment		AOCI*	AOCI* Cumulative Effect, Period of Adoption, Adjustment	Noncontrolling Interests
Beginning Balance at Dec. 31, 2017		$ 338.2	$ 2.2		$ 50.5	$ 628.6	$ 564.9	$ 3.3		$ (926.6)	$ (1.1)	$ 20.8
Beginning Balance (shares) at Dec. 31, 2017					50.5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		(27.5)					(33.3)					5.8
Other comprehensive loss		(16.5)								(15.7)		(0.8)
Stock Repurchased During Period, Value		(93.5)			$ (1.3)	(16.9)	(75.3)
Stock Repurchased During Period, Shares					(1.3)
Dividends to:
Brink’s common shareholders ($0.60 per share)		(30.4)					(30.4)
Noncontrolling interests		(5.2)										(5.2)
Stock options and awards:
Compensation expense		28.2				28.2
Consideration from exercise of stock options		0.8			$ 0.0	0.8
Consideration from exercise of stock options (shares)					0.0
Other share-based benefit transactions		(9.4)			$ 0.5	(9.8)	(0.1)
Other share-based benefit transactions (shares)					0.5
Dispositions of noncontrolling interests		(0.4)										(0.4)
Acquisitions of noncontrolling interests		(21.0)				(2.7)				(9.9)		(8.4)
Acquisitions with noncontrolling interests		1.1										1.1
Ending Balance at Dec. 31, 2018		$ 166.6			$ 49.7	628.2	429.1			(953.3)		12.9
Ending Balance (shares) at Dec. 31, 2018					49.7
Stock options and awards:
Brink's common shareholders per share declared (dollars per share)		$ 0.60
Tax cuts and jobs act, reclassification from AOCI to retained earnings, tax effect	[1]		0.0					28.8			(28.8)
Net income (loss)		$ 33.2					29.0					4.2
Other comprehensive loss		3.9								3.1		0.8
Stock Repurchased During Period, Value		0.0			$ 0.0	(0.5)	0.5
Stock Repurchased During Period, Shares					0.0
Brink’s common shareholders ($0.60 per share)		(29.9)					(29.9)
Noncontrolling interests		(2.3)										(2.3)
Compensation expense		42.7				42.7
Other share-based benefit transactions		(6.8)			$ 0.4	(7.1)	(0.1)
Other share-based benefit transactions (shares)					0.4
Capital contributions from noncontrolling interest		0.2										0.2
Ending Balance at Dec. 31, 2019		$ 207.6	$ (1.7)	[2]	$ 50.1	663.3	457.4	$ (1.7)	[2]	(979.0)	$ (28.8)	15.8
Ending Balance (shares) at Dec. 31, 2019					50.1
Stock options and awards:
Brink's common shareholders per share declared (dollars per share)		$ 0.60
Accounting Standards Update		us-gaap:AccountingStandardsUpdate201613Member
Net income (loss)		$ 21.9					16.0					5.9
Other comprehensive loss		(16.2)								(21.0)		4.8
Stock Repurchased During Period, Value		(50.0)			$ (1.1)	(14.9)	(34.0)
Stock Repurchased During Period, Shares					(1.1)
Brink’s common shareholders ($0.60 per share)		(30.1)					(30.1)
Noncontrolling interests		(16.8)										(16.8)
Compensation expense		31.3				31.3
Other share-based benefit transactions		(7.5)			$ 0.5	(7.9)	(0.1)
Other share-based benefit transactions (shares)					0.5
Acquisitions with noncontrolling interests		64.0										64.0
Ending Balance at Dec. 31, 2020		$ 202.5			$ 49.5	$ 671.8	$ 407.5			$ (1,000.0)		$ 73.7
Ending Balance (shares) at Dec. 31, 2020					49.5
Stock options and awards:
Brink's common shareholders per share declared (dollars per share)		$ 0.60

[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.

[2] Effective January 1, 2019, we adopted the provisions of ASU 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. We recognized a cumulative effect adjustment to January 1, 2019 retained earnings as a result of adopting this standard. See Note 1 for further details.(c)Effective January 1, 2020, we adopted the provisions of ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. We recognized a cumulative effect adjustment to January 1, 2020 retained earnings as a result of adopting this standard. See Note 1 for further details.