Reserves for Credit Losses (Details 3) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Provisions	$ (14.0)	$ 103.0
Card Member Loans
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	20.0	17.0
Provisions	8.0	3.0
Net write-offs	(4.0)	(2.0)
Ending Balance	24.0	18.0
Recoveries	$ 0.7	$ 0.5

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	instant

- Definition

Amount of increase in allowance for credit loss on financing receivable from recovery.

+ References

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of writeoff of financing receivable, charged against allowance for credit loss.

+ References

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- Definition

Amount of credit loss expense (reversal of expense) for financing receivable.

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- Details

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Period Type: