Loan Receivables (Schedule of Changes in the Allowance for Credit Losses) (Details) - USD ($) $ in Millions				3 Months Ended
		Jan. 01, 2020		Mar. 31, 2020		Mar. 31, 2020		Mar. 31, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, balance at beginning of period		$ 3,383	[1],[2],[3]	$ 5,844		$ 3,383	[1],[2],[3]	$ 3,041	[1]
Cumulative effect of ASU No. 2016-13 adoption		2,461	[4]			(1,902)
Provision for credit losses				1,838	[5]			809	[1]
Charge-offs				(975)				(887)
Recoveries				206				172
Net charge-offs				(769)				(715)	[6]
Other	[7]							(1)
Allowance for credit losses, balance at end of period		5,844		6,913	[2],[3]	6,913	[2],[3]	3,134	[1]
Credit loss build (release) on unfunded commitments	[1]					(31)
Credit Card Loans [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, balance at beginning of period		2,883	[1]	4,550		2,883	[1]	2,528	[1]
Cumulative effect of ASU No. 2016-13 adoption	[4]	1,667
Provision for credit losses				1,439	[5]			710	[1]
Charge-offs				(869)				(774)
Recoveries				186				158
Net charge-offs				(683)				(616)
Other								0
Allowance for credit losses, balance at end of period		4,550		5,306		5,306		2,622	[1]
Total Other Loans [Member] | Student Loans [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, balance at beginning of period		148	[1]	653		148	[1]	169	[1]
Cumulative effect of ASU No. 2016-13 adoption	[4]	505
Provision for credit losses				129	[5]			15	[1]
Charge-offs				(22)				(19)
Recoveries				5				4
Net charge-offs				(17)				(15)	[6]
Other	[7]							(1)
Allowance for credit losses, balance at end of period		653		765		765		168	[1]
Total Other Loans [Member] | Personal Loans [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, balance at beginning of period		348	[1]	613		348	[1]	338	[1]
Cumulative effect of ASU No. 2016-13 adoption	[4]	265
Provision for credit losses				263	[5]			84	[1]
Charge-offs				(84)				(94)
Recoveries				15				10
Net charge-offs				(69)				(84)
Other								0
Allowance for credit losses, balance at end of period		613		807		807		338	[1]
Total Other Loans [Member] | Other Loans [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, balance at beginning of period		4	[1]	28		4	[1]	6	[1]
Cumulative effect of ASU No. 2016-13 adoption	[4]	24
Provision for credit losses				7	[5]			0	[1]
Charge-offs				0				0
Recoveries				0				0
Net charge-offs				0				0
Other								0
Allowance for credit losses, balance at end of period		$ 28		$ 35		$ 35		$ 6	[1]

[1] Prior to adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach.

[2] Prior to adoption of Accounting Standards Update ("ASU") No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach.

[3] Prior to adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach.

[4] Represents the adjustment to allowance for credit losses as a result of adoption of ASU No. 2016-13 on January 1, 2020.

[5] Excludes a $31 million release of the liability for expected credit losses on unfunded commitments for the three months ended March 31, 2020 as the liability is recorded in accrued expenses and other liabilities in the Company's condensed consolidated statements of financial condition.

[6] Prior to adoption of ASU No. 2016-13 on January 1, 2020, net charge-offs on PCD loans generally did not result in a charge to earnings.

[7] Net change in reserves on PCD pools having no remaining non-accretable difference (prior to adoption of ASU No. 2016-13 on January 1, 2020).