Reserves for Losses - Changes in Card Member Loans Reserve for Losses (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for Loan and Lease Losses [Roll Forward]
Balance, January 1	$ 5.0	$ 5.0	$ 5.0
Provisions	14.0	6.0	6.0
Net write-offs	(9.0)	(6.0)	(6.0)
Balance, December 31	10.0	5.0	5.0
Allowance for card member loans, recoveries of bad debts	$ 1.6	$ 1.8	$ 1.0

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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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, after recoveries, of loans and leases that have been written-off.

+ References

No definition available.

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- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

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- Definition

Amount of expense related to estimated loss from loan and lease transactions.

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