Segment Information - (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021		Sep. 30, 2020
Summary of Segment Information
Total revenue	$ 958.2	$ 995.2	$ 2,845.6		$ 2,796.4
Operating income (loss) / Segment operating profit	(38.7)	(23.8)	(87.8)		(18.3)
Asset Impairment Charges	0.3	4.1	0.3		4.1
Restructuring and DN Now transformation expenses	0.0	(13.8)	(23.1)		(35.3)
Other income (expense)	(41.3)	(146.2)	(137.2)		(240.6)
Income (loss) from continuing operations before taxes	(2.6)	(122.4)	(49.4)		(222.3)
Eurasia Banking
Summary of Segment Information
Total revenue	323.5	364.2	977.3		1,012.4
Americas Banking
Summary of Segment Information
Total revenue	346.6	368.5	970.8		1,044.6
Retail
Summary of Segment Information
Total revenue	288.1	262.5	897.5		739.4
Operating Segments [Member]
Summary of Segment Information
Intersegment revenue	40.9	37.5	117.2		96.2
Operating income (loss) / Segment operating profit	(89.8)	(108.7)	(263.4)		(292.8)
Operating Segments [Member] | Eurasia Banking
Summary of Segment Information
Total revenue	323.5	364.2	977.3		1,012.4
Intersegment revenue	36.9	32.9	109.3		86.7
Operating income (loss) / Segment operating profit	(26.7)	(45.8)	(77.9)		(105.7)
Operating Segments [Member] | Americas Banking
Summary of Segment Information
Total revenue	346.6	368.5	970.8		1,044.6
Intersegment revenue	4.0	4.6	7.9		9.5
Operating income (loss) / Segment operating profit	(32.1)	(42.6)	(99.2)		(145.5)
Operating Segments [Member] | Retail
Summary of Segment Information
Total revenue	288.1	262.5	897.5		739.4
Operating income (loss) / Segment operating profit	(31.0)	(20.3)	(86.3)		(41.6)
Corporate and Reconciling Items [Member]
Summary of Segment Information
Reconciliation Of Operating Profit Loss From Segments To Consolidated, Amount	(51.1)	(84.9)	(175.6)		(274.5)
Corporate
Summary of Segment Information
Operating income (loss) / Segment operating profit	(8.2)	(19.2)	39.8	[1]	42.1	[1]
Segment Reconciling Items [Member]
Summary of Segment Information
Asset Impairment Charges	0.3	4.1	0.3		4.1
Restructuring and DN Now transformation expenses	(20.9)	(41.8)	(74.4)		(110.2)
Net non-routine expense	$ (21.7)	$ (19.8)	$ (61.1)		$ (118.1)

[1] Corporate charges not allocated to segments include headquarter-based costs associated with human resources, compensation and benefits, finance and accounting, global development/engineering, global strategy/mergers and acquisitions, global IT, tax, treasury and legal.