Goodwill and Other Assets (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Line Items]
Goodwill	$ 1,242.3	$ 1,271.3	$ 1,234.9
Accumulated impairment losses	(470.9)	(470.9)	(470.9)
Beginning balance	800.4	764.0
Transferred to assets held for sale	0.0	(1.4)
Divestitures	(0.3)	(10.0)
Currency translation adjustment	(28.7)	47.8
Ending balance	771.4	800.4
Eurasia Banking
Goodwill [Line Items]
Goodwill	579.0	590.4	579.2
Accumulated impairment losses	(291.7)	(291.7)	(291.7)
Beginning balance	298.7	287.5
Transferred to assets held for sale	0.0	(1.4)
Divestitures	0.0	(6.4)
Currency translation adjustment	(11.4)	19.0
Ending balance	287.3	298.7
Americas Banking
Goodwill [Line Items]
Goodwill	435.2	444.7	431.3
Accumulated impairment losses	(122.0)	(122.0)	(122.0)
Beginning balance	322.7	309.3
Transferred to assets held for sale	0.0	0.0
Divestitures	0.0	(2.4)
Currency translation adjustment	(9.5)	15.8
Ending balance	313.2	322.7
Retail
Goodwill [Line Items]
Goodwill	228.1	236.2	224.4
Accumulated impairment losses	(57.2)	(57.2)	$ (57.2)
Beginning balance	179.0	167.2
Transferred to assets held for sale	0.0	0.0
Divestitures	(0.3)	(1.2)
Currency translation adjustment	(7.8)	13.0
Ending balance	$ 170.9	$ 179.0