Discover Financial Services (DFS) 10-K 17 Feb 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information Document - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 12, 2021
Document Information [Line Items]
Document type	10-K
Document annual report	true
Document period end date	Dec. 31, 2020
Document transition report	false
Entity file number	001-33378
Entity registrant name	DISCOVER FINANCIAL SERVICES
Entity incorporation, state	DE
Entity tax identification number	36-2517428
Entity address, address line one	2500 Lake Cook Road
Entity address, city or town	Riverwoods
Entity address, state or province	IL
Entity address, postal zip code	60015
Entity phone number, city area code	224
Entity phone number, local phone number	405-0900
Title of 12(b) security	Common Stock, par value $0.01 per share
Trading symbol	DFS
Security exchange name	NYSE
Entity well-known seasoned issuer	Yes
Entity voluntary filers	No
Entity current reporting status	Yes
Entity interactive data current	Yes
Entity filer category	Large Accelerated Filer
Smaller reporting company	false
Emerging growth company	false
ICFR Auditor Attestation Flag	true
Entity shell company	false
Entity public float	$ 15,308,066,731
Entity common stock, shares outstanding		306,691,722
Entity central index key	0001393612
Current fiscal year end date	--12-31
Document fiscal year focus	2020
Document fiscal period focus	FY
Amendment flag	false

Consolidated Statements of Fina

Consolidated Statements of Financial Condition - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Assets
Cash and cash equivalents		$ 13,564	$ 6,924
Restricted cash		25	40
Other short-term investments		2,200	0
Investment securities (includes available-for-sale securities of $9,654 and $10,323 reported at fair value with associated amortized cost of $9,277 and $10,173 at December 31, 2020 and 2019, respectively)		9,914	10,595
Loan receivables
Loan receivables		90,449	95,894
Allowance for credit Loss	[1],[2]	(8,226)	(3,383)	[3]
Net loan receivables		82,223	92,511
Premises and equipment, net		1,027	1,057
Goodwill		255	255
Intangible assets, net		95	155
Other assets		3,586	2,459
Total assets		112,889	113,996
Deposits
Interest-bearing deposit accounts		75,695	71,955
Non-interest bearing deposit accounts		1,209	791
Total deposits		76,904	72,746
Long-term borrowings		21,241	25,701
Accrued expenses and other liabilities		3,860	3,690
Total liabilities		102,005	102,137
Commitments, contingencies and guarantees (Notes 15, 18 and 19)
Stockholders’ Equity
Common stock, par value $0.01 per share; 2,000,000,000 shares authorized; 567,898,063 and 566,653,650 shares issued at December 31, 2020 and 2019, respectively		6	6
Preferred stock, par value $0.01 per share; 200,000,000 shares authorized; 10,700 and 5,700 shares issued and outstanding at December 31, 2020 and 2019, respectively		1,056	563
Additional paid-in capital		4,257	4,206
Retained earnings		19,955	21,290
Accumulated other comprehensive income (loss)		45	(119)
Treasury stock, at cost; 261,300,765 and 256,496,492 shares at December 31, 2020 and 2019, respectively		(14,435)	(14,087)
Total stockholders’ equity		10,884	11,859
Total liabilities and stockholders’ equity		112,889	113,996
Variable Interest Entity, Primary Beneficiary [Member]
Assets
Restricted cash		25	40
Loan receivables
Loan receivables		27,546	31,840
Allowance for credit Loss	[2]	(1,936)	(1,179)
Other assets		4	5
Deposits
Long-term borrowings		10,840	14,284
Accrued expenses and other liabilities		$ 8	$ 15
[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 the adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach.

Consolidated Statements of Fi_2

Consolidated Statements of Financial Condition (Parenthetical) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Available-for-sale investment securities, fair value	[1]	$ 9,654	$ 10,323
Debt Securities, available-for-sale, amortized cost	[1]	$ 9,277	$ 10,173
Common Stock, par or stated value per share		$ 0.01	$ 0.01
Common stock, shares authorized		2,000,000,000	2,000,000,000
Common stock, shares, issued		567,898,063	566,653,650
Preferred Stock, par or stated value per share		$ 0.01	$ 0.01
Preferred stock, shares authorized		200,000,000	200,000,000
Preferred stock, shares issued		10,700	5,700
Preferred stock, shares outstanding		10,700	5,700
Treasury stock, shares		261,300,765	256,496,492
[1]	Available-for-sale investment securities are reported at fair value.

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019		Dec. 31, 2018
Interest income
Credit card loans		$ 8,985	$ 9,690		$ 8,835
Other loans		1,817	1,871		1,726
Investment securities		252	179		40
Other interest income		41	253		292
Total interest income		11,095	11,993		10,893
Interest expense
Deposits		1,231	1,587		1,238
Short-term borrowings		32	0		0
Long-term borrowings		602	943		901
Total interest expense		1,865	2,530		2,139
Net interest income		9,230	9,463		8,754
Provision for credit losses	[1],[2]	5,134	3,231	[3]	3,035	[3]
Net interest income after provision for credit losses		4,096	6,232		5,719
Other income
Discount and interchange revenue, net		933	1,066		1,074
Protection products revenue		180	194		204
Loan fee income		414	449		402
Transaction processing revenue		195	197		178
Gains (losses) on equity investments		80	(3)		0
Other income		56	93		97
Total other income		1,858	1,996		1,955
Other expense
Employee compensation and benefits		1,894	1,738		1,627
Marketing and business development		659	883		857
Information processing and communications		540	409		350
Professional fees		717	753		672
Premises and equipment		113	107		102
Other expense		596	503		469
Total other expense		4,519	4,393		4,077
Income before income tax expense		1,435	3,835		3,597
Income tax expense		294	878		855
Net income		1,141	2,957		2,742
Supplemental Income Statement Elements [Abstract]
Net income (loss) available to common stockholders, diluted		1,104	2,908		2,689
Net income (loss) available to common stockholders, basic		$ 1,104	$ 2,908		$ 2,689
Basic earnings per common share		$ 3.60	$ 9.09		$ 7.81
Diluted earnings per common share		$ 3.60	$ 9.08		$ 7.79
[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 ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach.
[3]	Prior to the adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net income	$ 1,141	$ 2,957	$ 2,742
Other comprehensive income, net of tax
Unrealized gains on available-for-sale investment securities, net of tax	172	102	16
Unrealized gains (losses) on cash flow hedges, net of tax	5	(39)	9
Unrealized pension and post-retirement plan (losses) gains, net of tax	(13)	(26)	0
Other comprehensive income, net	164	37	25
Comprehensive income	$ 1,305	$ 2,994	$ 2,767

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Retained Earnings [Member]Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Loss [Member]		Treasury Stock [Member]	Series C Preferred Stock [Member]	Series C Preferred Stock [Member]Retained Earnings [Member]
Preferred stock, shares outstanding, balance at beginning of period (in shares) at Dec. 31, 2017			6,000
Common stock, shares outstanding, balance at beginning of period (in shares) at Dec. 31, 2017				563,498,000
Stockholders' equity, balance at beginning of period at Dec. 31, 2017	$ 10,892		$ 563	$ 6	$ 4,042	$ 16,687		$ (152)		$ (10,254)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of ASU No. 2018-02 adoption	0					29		(29)	[1]
Net income	2,742					2,742
Other comprehensive income	25							25
Purchases of treasury stock	(2,065)									(2,065)
Common stock issued under employee benefit plans (in shares)				96,000
Common stock issued under employee benefit plans	6			$ 0	6
Common stock issued and stock-based compensation expense (in shares)				1,258,000
Common stock issued and stock-based compensation expense	82			$ 0	82
Dividends — common stock	(521)					(521)
Dividends — preferred stock	(31)										$ (31)	$ (31)
Preferred stock, shares outstanding, balance at end of period (in shares) at Dec. 31, 2018			6,000
Common stock, shares outstanding, balance at end of period (in shares) at Dec. 31, 2018				564,852,000
Stockholders' equity, balance at end of period at Dec. 31, 2018	11,130		$ 563	$ 6	4,130	18,906		(156)		(12,319)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,957					2,957
Other comprehensive income	37							37
Purchases of treasury stock	(1,768)									(1,768)
Common stock issued under employee benefit plans (in shares)				97,000
Common stock issued under employee benefit plans	7			$ 0	7
Common stock issued and stock-based compensation expense (in shares)				1,705,000
Common stock issued and stock-based compensation expense	69			$ 0	69
Dividends — common stock	(542)					(542)
Dividends — preferred stock	$ (31)										(31)	(31)
Preferred stock, shares outstanding, balance at end of period (in shares) at Dec. 31, 2019	5,700		6,000
Common stock, shares outstanding, balance at end of period (in shares) at Dec. 31, 2019				566,654,000
Stockholders' equity, balance at end of period at Dec. 31, 2019	$ 11,859		$ 563	$ 6	4,206	21,290		(119)		(14,087)
Stockholders' equity, balance at end of period (Accounting Standards Update 2016-13 [Member]) at Dec. 31, 2019		$ (1,902)					$ (1,902)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,141					1,141
Other comprehensive income	164							164
Purchases of treasury stock	(348)									(348)
Common stock issued under employee benefit plans (in shares)				192,000
Common stock issued under employee benefit plans	10			$ 0	10
Common stock issued and stock-based compensation expense (in shares)				1,052,000
Common stock issued and stock-based compensation expense	41			$ 0	41
Dividends — common stock	(543)					(543)
Dividends — preferred stock	$ (31)										$ (31)	$ (31)
Preferred stock, shares outstanding, balance at end of period (in shares) at Dec. 31, 2020	10,700		11,000
Common stock, shares outstanding, balance at end of period (in shares) at Dec. 31, 2020				567,898,000
Stockholders' equity, balance at end of period at Dec. 31, 2020	$ 10,884		$ 1,056	$ 6	$ 4,257	$ 19,955		$ 45		$ (14,435)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Series D preferred stock (in shares)			5,000
Issuance of Series D preferred stock	$ 493		$ 493
[1]	Represents the adjustment to AOCI as a result of adoption of ASU No. 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income, in the second quarter of 2018.

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Stockholders' Equity (Parentheticals) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Common stock, dividends, per share, declared	$ 1.76	$ 1.68	$ 1.50
Series C Preferred Stock [Member]
Preferred stock, dividends per share, declared	$ 5,500	$ 5,500	$ 5,500

Consolidated Statements of Cash

Consolidated Statements of Cash Flows $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)		Dec. 31, 2019USD ($)		Dec. 31, 2018USD ($)
Cash flows provided by operating activities
Net income	$ 1,141		$ 2,957		$ 2,742
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	5,134	[1],[2]	3,231	[1],[2],[3]	3,035	[1],[2],[3]
Deferred income taxes	(672)		(133)		(190)
Depreciation and amortization	485		436		435
Amortization of deferred revenues and accretion of accretable yield on acquired loans	(320)		(421)		(403)
Net (gains) losses on investments and other assets	(26)		37		45
Other, net	200		82		83
Changes in assets and liabilities:
Decrease (increase) in other assets	118		(202)		(7)
Increase (decrease) in accrued expenses and other liabilities	136		209		(549)
Net cash provided by operating activities	6,196		6,196		5,191
Cash flows provided by (used for) investing activities
Maturities of other short-term investments	5,850		1,000		0
Purchases of other short-term investments	(8,046)		(1,000)		0
Maturities of available-for-sale investment securities	1,007		140		838
Purchases of available-for-sale investment securities	(113)		(7,183)		(2,554)
Maturities of held-to-maturity investment securities	54		31		18
Purchases of held-to-maturity investment securities	(44)		(66)		(82)
Net principal repaid (disbursed) on loans originated for investment	3,045		(7,844)		(8,480)
Proceeds from returns of investment	94		0		0
Purchases of other investments	(72)		(68)		(65)
Purchases of premises and equipment	(261)		(284)		(254)
Net cash provided by (used for) investing activities	1,514		(15,274)		(10,579)
Cash flows (used for) provided by financing activities
Proceeds from issuance of securitized debt	0		3,519		4,766
Maturities and repayment of securitized debt	(3,531)		(6,287)		(4,447)
Proceeds from issuance of other long-term borrowings	494		1,340		2,233
Maturities and repayment of other long-term borrowings	(1,755)		(286)		(1,756)
Proceeds from issuance of common stock	10		7		6
Purchases of treasury stock	(348)		(1,768)		(2,065)
Net increase in deposits	4,128		4,945		8,961
Proceeds from issuance of preferred stock	493		0		0
Dividends paid on common and preferred stock	(576)		(573)		(552)
Net cash (used for) provided by financing activities	(1,085)		897		7,146
Net increase (decrease) in cash, cash equivalents and restricted cash	6,625		(8,181)		1,758
Cash, cash equivalents and restricted cash, at beginning of period	6,964		15,145		13,387
Cash, cash equivalents and restricted cash, at end of period	13,589		6,964		15,145
Reconciliation of cash, cash equivalents and restricted cash
Cash and cash equivalents	13,564		6,924		13,299
Restricted cash	25		40		1,846
Cash paid during the period for
Interest expense	1,799		2,407		1,847
Income taxes, net of income tax refunds	$ 901		$ 1,088		$ 650
[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 ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach.
[3]	Prior to the adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach

Background and Basis of Present

Background and Basis of Presentation	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Background and Basis of Presentation	Background and Basis of Presentation Description of Business Discover Financial Services (“DFS” or the “Company”) is a digital banking and payment services company. The Company is a bank holding company under the Bank Holding Company Act of 1956 as well as a financial holding company under the Gramm-Leach-Bliley Act and therefore is subject to oversight, regulation and examination by the Board of Governors of the Federal Reserve System (the “Federal Reserve”). The Company provides digital banking products and services and payment services through its subsidiaries. The Company offers its customers credit card loans, private student loans, personal loans, home loans and deposit products. The Company also operates the Discover Network, the PULSE network (“PULSE”) and Diners Club International (“Diners Club”), collectively known as the Discover Global Network. The Discover Network processes transactions for Discover-branded credit and debit cards and provides payment transaction processing and settlement services. PULSE operates an electronic funds transfer network, providing financial institutions issuing debit cards on the PULSE network with access to ATMs domestically and internationally, as well as merchant acceptance throughout the United States for debit card transactions. Diners Club is a global payments network of licensees, which are generally financial institutions, that issue Diners Club branded charge cards and/or provide card acceptance services. The Company’s business activities are managed in two segments, Digital Banking and Payment Services, based on the products and services provided. For a detailed description of the operations of each segment, as well as the allocation conventions used in business segment reporting, see Note 22: Segment Disclosures. Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”). The preparation of financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and related disclosures. These estimates are based on information available as of the date of the consolidated financial statements. The Company believes that the estimates used in the preparation of the consolidated financial statements are reasonable. Actual results could differ from these estimates. Principles of Consolidation The accompanying consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. The Company’s policy is to consolidate all entities in which it owns more than 50% of the outstanding voting stock unless it does not control the entity. However, the Company did not have a controlling voting interest in any entity other than its wholly-owned subsidiaries in the periods presented in the accompanying consolidated financial statements. It is also the Company’s policy to consolidate any VIEs for which the Company is the primary beneficiary, as defined by GAAP. On this basis, the Company consolidates the Discover Card Master Trust I (“DCMT”) and the Discover Card Execution Note Trust (“DCENT”) as well as the student loan securitization trust. The Company is deemed to be the primary beneficiary of each of these trusts since it is, for each, the trust Servicer and the holder of both the residual interest and the majority of the most subordinated interests. Because of those involvements, the Company has, for each trust, (i) the power to direct the activities that most significantly impact the economic performance of the trust and (ii) the obligation (or right) to absorb losses (or receive benefits) of the trust that could potentially be significant. The Company has determined that it was not the primary beneficiary of any other VIE during the years ended December 31, 2020, 2019 and 2018. For investments in any entities in which the Company owns 50% or less of the outstanding voting stock but in which the Company has significant influence over operating and financial decisions, the Company applies the equity method of accounting. The Company also applies the equity method to its investments in qualified affordable housing projects and similar tax credit partnerships. In cases where the Company’s equity investment is less than 20% and significant influence does not exist, such investments are carried at cost as they typically do not have readily determinable fair values, and are adjusted for any impairment in value. Recently Adopted Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The FASB subsequently issued several additional ASUs that clarify the scope and application of the new credit loss guidance. Topic 326 replaced the incurred loss model with the current expected credit loss (“CECL”) approach. For loans carried at amortized cost, the allowance for credit losses is now based on management’s current estimate of all anticipated credit losses over the remaining expected life of the loans. Upon the origination of a loan, the Company will record its estimate of all expected credit losses on that loan through an immediate charge to earnings. Updates to that estimate each period will be recorded through provision expense. The CECL estimate is based on historical experience, current conditions and reasonable and supportable forecasts. As compared to prior GAAP, the CECL approach increases the Company’s allowance for credit losses on loan receivables as a result of: (i) recording reserves for expected losses, not simply those deemed to be already incurred, (ii) extending the loss estimate period over the entire life of the loan and (iii) presenting the credit loss component of the purchased credit-impaired (“PCI”) loan portfolio in the allowance for credit losses rather than embedding it within the loan carrying value. The allowance for credit losses on all loans carried at amortized cost, including loans previously referred to as PCI loans and loans modified in a troubled debt restructuring (“TDR”) are measured under the CECL approach. Previous specialized measurement guidance for PCI loans, which are now referred to as purchased credit-deteriorated (“PCD”), and TDRs was eliminated, although certain separate disclosure guidance was retained. Measurement of credit impairment of available-for-sale debt securities generally remains unchanged under the new rules, but any credit impairment is recorded through an allowance, rather than a direct write-down of the security. The Company invests in United States Treasury obligations and residential mortgage-backed securities issued by government agencies, which have long histories with no credit losses and are explicitly or implicitly guaranteed by the United States government. Therefore, management has concluded that there is no expectation of non-payment on its investment securities and does not record an allowance for credit losses on these investments. The ASU became effective for the Company on January 1, 2020, and required modified-retrospective application, meaning a cumulative-effect adjustment was recorded as of the effective date without adjusting comparative prior periods. This cumulative-effect adjustment did not reflect the economic disruption resulting from the coronavirus disease 2019 (“COVID-19”) since the global disruption occurred subsequent to January 1, 2020. As a result of adoption, the Company recorded: • A $2.5 billion increase to the allowance for credit losses primarily representing the adjustment for recording reserves for expected losses, not simply those deemed to be already incurred, and extending the loss estimate period over the entire life of the loan; • A $0.6 billion increase to other assets related to deferred tax assets on the larger allowance for credit losses; • An offsetting $1.9 billion decrease, net of tax, to the opening balance of retained earnings; and • Immaterial adjustments to the following: • The carrying value of PCD loans and related accrued interest reflected in other assets; and • Accrued expenses and other liabilities to record reserves for unfunded commitments. As required by the ASU, financial statement results and balances prior to January 1, 2020, have not been retrospectively adjusted to reflect the amendments in ASU No. 2016-13. Therefore, current period results and balances are not comparable to prior period amounts, particularly with regard to the provision and allowance for credit losses (and their related subtotals) In January 2021, the Financial Accounting Standards Board ("FASB") issued ASU No. 2021-01, R eference Rate Reform (Topic 848): Scope . The ASU clarifies that certain optional expedients and exceptions provided in Topic 848 (see discussion below pertaining to ASU No. 2020-04) also apply to derivatives that do not reference a rate that is being discontinued but otherwise are affected by reference rate reform. The ASU clarifies that changes in the interest rates used for margining, discounting, or contract price alignment for derivative instruments that are being implemented as part of the market-wide transition to new reference rates (commonly referred to as the “discounting transition”) are within the scope of Topic 848. The ASU was effective upon issuance and was retrospectively adopted as of October 1, 2020. It was initially applied in October 2020 with the election of optional relief from contract modification accounting for eligible interest rate swaps affected by a change in discounting methodology. The Company does not expect there to be a material impact to the financial statements. See Note 20: Fair Value Measurements for more information. In March 2020, the FASB issued ASU No. 2020-04, R eference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting . The ASU addresses operational challenges resulting from the discontinuation of the London Interbank Offered Rate (“LIBOR”) and other reference rates at the end of 2021. By providing optional practical expedients and exceptions to applying certain GAAP requirements, ASU No. 2020-04 provides temporary relief designed to ease the operational cost and burden of accounting for contract modifications, hedging relationships and other transactions that reference LIBOR or another reference rate expected to be discontinued as a result of reference rate reform. In general, the optional expedients and exceptions allow eligible contracts that are modified due to reference rate reform to be accounted for prospectively as a continuation of those contracts, permit companies to preserve hedge accounting for hedging relationships affected by reference rate reform and enable companies to make a one-time election to transfer or sell certain held-to-maturity debt securities indexed to LIBOR or another reference rate that is expected to be discontinued. The temporary expedients and exceptions are elective and do not apply to contract modifications made and hedging relationships entered into or evaluated after December 31, 2022, with the exception of hedging relationships existing as of that date for which certain optional expedients have been elected and are expected to be retained through the end of the hedging relationships. The ASU became effective upon issuance and it was initially applied by the Company in October 2020 with the election of optional relief from contract modification accounting for eligible interest rate swaps affected by a change in discounting methodology. As part of its overall evaluation of reference rate reform, management is still evaluating the impact that LIBOR replacement will have on the Company’s financial statements. Any such impacts will be prospective in nature and the Company expects it to affect net interest income and fair value estimates after the effective date of such rate replacement. The Company does not expect there to be a material impact to the financial statements.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Cash and Cash Equivalents Cash and cash equivalents is defined by the Company as cash on deposit with banks, including time deposits and other highly liquid investments, with maturities of 90 days or less when purchased, excluding amounts restricted by certain contractual or other obligations. Cash and cash equivalents included $1.1 billion and $959 million of cash and due from banks and $12.5 billion and $6.0 billion of interest-earning deposits at other banks at December 31, 2020 and 2019, respectively. Restricted Cash Restricted cash includes cash for which the Company’s ability to withdraw funds at any time is contractually limited. Restricted cash is generally designated for specific purposes arising out of certain contractual or other obligations. Investment Securities At December 31, 2020, investment securities consisted of United States Treasury obligations and mortgage-backed securities issued by government agencies. Investment securities that the Company has the positive intent and ability to hold to maturity are classified as held-to-maturity and are reported at amortized cost. All other investment securities are classified as available-for-sale, as the Company does not hold investment securities for trading purposes. Available-for-sale investment securities are reported at fair value with unrealized gains and losses, net of tax, reported as a component of accumulated other comprehensive income (“AOCI”) included in stockholders’ equity. The Company estimates the fair value of available-for-sale investment securities as more fully discussed in Note 20: Fair Value Measurements. The amortized cost for each held-to-maturity and available-for-sale investment security is adjusted for amortization of premiums or accretion of discounts, as appropriate. Such amortization or accretion is included in interest income. The United States Treasury obligations and residential mortgage-backed securities issued by government agencies in which the Company invests have long histories with no credit losses and are explicitly or implicitly guaranteed by the United States government. Therefore, management has concluded that there is no expectation of non-payment on its investment securities and does not record an allowance for credit losses on these investments. Loan Receivables Loan receivables consist of credit card receivables and other loan receivables. Loan receivables also include unamortized net deferred loan origination fees and costs (also see “— Significant Revenue Recognition Accounting Policies — Loan Interest and Fee Income”). Credit card loan receivables are reported at their principal amounts outstanding and include uncollected billed interest and fees and are reduced for unearned revenue related to balance transfer fees (also see “— Significant Revenue Recognition Accounting Policies — Loan Interest and Fee Income”). Other loans consist of private student loans, personal loans and other loans and are reported at their principal amounts outstanding. For private student loans, principal amounts outstanding also include accrued interest that has been capitalized. The Company’s loan receivables are deemed to be held for investment at origination or acquisition because management has the intent and ability to hold them for the foreseeable future. Cash flows associated with loans originated or acquired for investment are classified as cash flows from investing activities, regardless of a subsequent change in intent. Delinquent Loans and Charge-Offs The entire balance of an account is contractually past due if the minimum payment is not received by the specified date on the customer’s billing statement. Delinquency is reported on loans that are 30 days or more past due. Credit card loans are charged off at the end of the month during which an account becomes 180 days past due. Closed-end unsecured consumer loan receivables are charged off at the end of the month during which an account becomes 120 days contractually past due. Customer bankruptcies and probate accounts are charged off by the end of the month 60 days following the receipt of notification of the bankruptcy or death, but not later than the 180-day or 120-day time frame described above. Receivables associated with alleged or potential fraudulent transactions are adjusted to their net realizable value upon receipt of notification of such fraud through a charge to other expense and are subsequently written off at the end of the month 90 days following notification, but not later than the contractual 180-day or 120-day time frame described above. The Company’s charge-off policies are designed to comply with guidelines established by the Federal Financial Institutions Examination Council (“FFIEC”). The Company’s net charge-offs include the principal amount of loans charged off less principal recoveries and exclude charged-off interest and fees, recoveries of interest and fees and fraud losses. The practice of re-aging an account also may affect loan delinquencies and charge-offs. A re-age is intended to assist delinquent customers who have experienced financial difficulties but who demonstrate both an ability and willingness to repay. Accounts meeting specific criteria are re-aged when the Company and the customer agree on a temporary repayment schedule that may include concessionary terms. With re-aging, the outstanding balance of a delinquent account is returned to a current status. Customers may also qualify for a workout re-age when either a longer term or permanent hardship exists. The Company’s re-age practices are designed to comply with FFIEC guidelines. Allowance for Credit Losses The Company maintains an allowance for credit losses at a level that is appropriate to absorb net credit losses anticipated over the remaining expected life of loan receivables as of the balance sheet date. The estimate of expected credit losses considers uncollectible principal, interest and fees associated with the Company's loan receivables existing as of the balance sheet date. Additionally, the estimate includes expected recoveries of amounts that were either previously charged off or are expected to be charged off. The allowance is evaluated quarterly for appropriateness and is maintained through an adjustment to the provision for credit losses. Charge-offs of principal amounts of loans outstanding are deducted from the allowance and subsequent recoveries of such amounts increase the allowance. Charge-offs of loan balances representing unpaid interest and fees result in a reversal of interest and fee income, respectively, which is effectively a reclassification of the provision for credit losses. The Company calculates its allowance for credit losses by estimating expected credit losses separately for classes of receivables with similar risk characteristics. This results in segmenting the portfolio by loan product type, which is the level that the Company develops and documents its methodology for determining the allowance for credit losses. The estimate of expected credit losses for each loan product type is based on: (i) a reasonable and supportable forecast period; (ii) a reversion period; and (iii) a post-reversion period based on historical information covering the remaining life of the loan, all of which is netted with expected recoveries. The lengths of the reasonable and supportable forecast and reversion periods can vary and are subject to a quarterly assessment that considers the economic outlook and level of variability among macroeconomic forecasts. Generally, a straight-line method is used to revert from the reasonable and supportable forecast period to the post-reversion period, but in certain stressed scenarios, a weighted approach may be deemed more appropriate. Several analyses are used to help estimate credit losses anticipated over the remaining expected life of loan receivables as of the balance sheet date. The Company's estimation process includes models that predict customer losses based on risk characteristics and portfolio attributes, macroeconomic variables and historical data and analysis. There is a significant amount of judgment applied in selecting inputs and analyzing the results produced by the models to determine the allowance. For credit card loans, the Company uses a modeling framework that includes the following components for estimating expected credit losses: • Probability of default: this component estimates the probability of charge-off at different points in time over the life of each loan. • Exposure at default: this component estimates the portion of the balance sheet date balance remaining at any given time of charge-off for each loan. Given that there is no stated life of a receivable balance on a revolving credit card account, the Company applies a percentage of expected payments to estimate the portion of the balance that would remain at the time of charge-off. • Loss given default: this component estimates the percentage of exposure (i.e., net loss) at time of charge-off that cannot be recovered, with the offsetting forecast recoveries being the driver of this estimate. • Recoveries from previously charged-off accounts are estimated separately and are netted as part of the aggregation of all of the components of the card loss modeling framework. For private student loans and personal loans, the Company uses vintage-based models that estimate expected credit losses over the life of the loan, net of recovery estimates, impacted mainly by time elapsed since origination, credit quality of origination vintages and macroeconomic forecasts. The components described above for credit card, private student and personal loans are developed utilizing historical data and applicable macroeconomic variable inputs based on statistical analysis and customer behavioral relationships with credit performance. Expected recoveries from loans charged off as of the balance sheet date are modeled separately and included in the allowance estimate. The Company leverages these models and recent macroeconomic forecasts for the portion of the estimate associated with the reasonable and supportable forecast period. To estimate expected credit losses for the remainder of the life of the credit card loans, the Company reverts to historical experience of credit card loans with characteristics similar to those as of the balance sheet date and observed over various phases of a credit cycle. To estimate expected credit losses for the remainder of the life of private student and personal loans, the Company reverts to use of average macroeconomic variables over an appropriate historical period. The considerations in these models include past and current loan performance, loan growth and seasoning, risk management practices, account collection strategies, economic conditions, bankruptcy filings, policy changes and forecasting uncertainties. Consideration of past and current loan performance includes the post-modification performance of loans modified in a troubled debt restructuring. For the credit card loan portfolio, the Company estimates its credit losses on a loan-level basis, which includes loans that are delinquent and/or no longer accruing interest and/or loans that have been restructured. For the remainder of its portfolio, including private student, personal and other loans, the Company estimates its credit losses on a pooled basis. For all loan types, recoveries are estimated at a pooled level based on estimates of future cash flows derived using historical experience. Accrued interest receivable on credit card loans is included in the estimate of expected credit losses once billed to the customer (i.e., once the interest becomes part of the loan balance). Except as noted in the following sentence, an allowance for credit losses is not recorded for unbilled credit card interest or accrued interest receivable on other loan classes as the impact to the allowance for credit losses is not material. Accrued interest receivable on student loans that have not yet entered repayment is included in the estimate of expected credit losses. No liability for expected credit losses is required for unused lines of credit on the Company’s credit card loans because they are unconditionally cancellable. The Company records a liability for expected credit losses for unfunded commitments on all other loans, which is presented as part of accrued expenses and other liabilities in the consolidated statements of financial condition. This liability is evaluated quarterly for appropriateness and is maintained through an adjustment to the provision for credit losses. As part of certain collection strategies, the Company may modify the terms of loans to customers experiencing financial hardship. Temporary and permanent modifications on credit card and personal loans, as well as temporary modifications on private student loans and certain grants of private student loan forbearance are accounted for as troubled debt restructurings. The Company classifies a modified loan in which a concession has been granted to the borrower as a troubled debt restructuring based on the cumulative length of the concession period and credit quality of the borrower. Loan receivables that have been modified are subject to the same requirements for the accrual of expected credit loss over their expected remaining lives as described above for unmodified loans. The effects of all loan modifications, including TDRs, loan modifications exempt from TDR status pursuant to the Coronavirus Aid, Relief, and Economic Security Act ("CARES Act”) and Skip-a-Pay (payment deferral) programs, are reflected in the allowance for credit losses. An adjustment to the allowance for credit losses is not recorded for reasonably expected TDRs as the impact is not material. When the impact of the concession can only be captured by use of a discounted cash flow method (or a reconcilable method), such method is used to measure the allowance for credit losses. Prior to the adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach. As required by the ASU, financial statement results and balances prior to January 1, 2020, have not been retrospectively adjusted to reflect the amendments in ASU No. 2016-13. Therefore, current period results and balances are not comparable to prior period amounts, particularly with regard to the provision and allowance for credit losses (and their related subtotals). See Note 2: Summary of Significant Accounting Policies to the consolidated financial statements of the Company's annual report on Form 10-K for the year ended December 31, 2019 for more information related to the incurred loss approach. Premises and Equipment, net Premises and equipment, net, are stated at cost less provisions for impairment and accumulated depreciation and amortization. Accumulated depreciation and amortization is computed using the straight-line method over the estimated useful lives of the assets. The Company periodically reviews the estimated useful lives and may adjust them as necessary. Buildings are depreciated over a period of thirty-nine years. The costs of improvements are capitalized and depreciated either over the asset’s estimated useful life, typically ten years to fifteen years, or over the remaining term of the lease, when applicable. Furniture and fixtures are depreciated over a period of five years to ten years. Equipment is depreciated over three years to ten years. Maintenance and repairs are immediately expensed when incurred, while the costs of significant improvements are capitalized. Purchased software and capitalized costs related to internally developed software are amortized over their useful lives of three years to ten years. Costs incurred during the application development stage related to internally developed software are capitalized. Costs are expensed as incurred during the preliminary project stage and post implementation stage. Once the capitalization criteria as defined in GAAP have been met, external direct costs incurred for materials and services used in developing or obtaining internal-use computer software and payroll and payroll-related costs for employees who are directly associated with the internal-use computer software project (to the extent those employees devoted time directly to the project) are capitalized. Amortization of capitalized costs begins when the software is ready for its intended use. Capitalized software is included in premises and equipment, net in the Company’s consolidated statements of financial condition. See Note 6: Premises and Equipment for further information about the Company’s premises and equipment. Cloud computing arrangements involving the licensing of software that meet certain criteria are recognized as the acquisition of software. Such assets are measured at the present value of the license obligation, if the license is to be paid over time, in addition to any capitalized upfront costs and amortized over the life of the arrangement. Cloud computing arrangements that do not meet the criteria to be recognized as acquired software are accounted for as service contracts. To date, none of the Company’s cloud computing arrangements have met the criteria to be recognized as acquired software. Premises and equipment are subject to impairment testing when events or conditions indicate that the carrying value of the asset may not be fully recoverable from future cash flows. See “— Intangible Assets” for additional details on impairment testing. Goodwill Goodwill is recorded as part of the Company’s acquisitions of businesses when the purchase price exceeds the fair value of the net tangible and separately identifiable intangible assets acquired. The Company’s goodwill is not amortized, but rather is subject to an impairment test at the reporting unit level annually as of October 1, or between annual tests if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. The Company’s reported goodwill relates to PULSE, which it acquired in 2005. The Company’s goodwill is tested for impairment by comparing the fair value of the reporting unit to its carrying value. If the fair value of the reporting unit exceeds its carrying value, goodwill is not impaired. If the carrying value exceeds its fair value, an impairment loss must be recognized in an amount equal to that excess, limited to the total amount of goodwill allocated to that reporting unit. No impairment was identified during the impairment test conducted as of October 1, 2020. Intangible Assets The Company’s identifiable intangible assets consist of both amortizable and non-amortizable intangible assets. The Company’s amortizable intangible assets consist primarily of acquired customer relationships and certain trade name intangibles. All of the Company’s amortizable intangible assets are carried at net book value and are amortized over their estimated useful lives. The amortization periods approximate the periods over which the Company expects to generate future net cash inflows from the use of these assets. The Company’s policy is to amortize intangibles in a manner that reflects the pattern in which the projected net cash inflows to the Company are expected to occur, where such pattern can be reasonably determined, as opposed to the straight-line basis. This method of amortization typically results in a greater portion of the intangible asset being amortized in the earlier years of its useful life. All of the Company’s amortizable intangible assets, as well as other amortizable or depreciable long-lived assets such as premises and equipment, are subject to impairment testing when events or conditions indicate that the carrying value of the asset may not be fully recoverable from future cash flows. A test for recoverability is done by comparing the asset’s carrying value to the sum of the undiscounted future net cash inflows expected to be generated from the use of the asset over its remaining useful life. Impairment exists if the sum of the undiscounted expected future net cash inflows is less than the carrying amount of the asset. Impairment would result in a write-down of the asset to its estimated fair value. The estimated fair values of these assets are based on the discounted present value of the stream of future net cash inflows expected to be derived over the remaining useful lives of the assets. If an impairment write-down is recorded, the remaining useful life of the asset will be evaluated to determine whether revision of the remaining amortization or depreciation period is appropriate. The Company’s non-amortizable intangible assets consist primarily of the brand-related intangibles and international transaction processing rights included in the acquisition of Diners Club. These assets are deemed to have indefinite useful lives and are therefore not subject to amortization. All of the Company’s non-amortizable intangible assets are subject to a test for impairment annually as of October 1, or more frequently if events or changes in circumstances indicate that the asset might be impaired. As required by GAAP, if the carrying value of a non-amortizable intangible asset is in excess of its fair value, the asset must be written down to its fair value through the recognition of an impairment charge to earnings. In contrast to amortizable intangibles, there is no test for recoverability associated with the impairment test for non-amortizable intangible assets. No significant impairment concerns were identified during the annual impairment test conducted as of October 1, 2020. See Note 7: Goodwill and Intangibles for additional details on the Company’s intangible assets. Stock-based Compensation The Company measures the cost of employee services received in exchange for an award of stock-based compensation based on the grant-date fair value of the award. The cost, net of estimated forfeitures, is recognized over the requisite service period. Awards to employees who are retirement-eligible at any point during the year are amortized over 12 months in accordance with the vesting terms that apply under those circumstances. No compensation cost is recognized for awards that are subsequently forfeited. Advertising Costs The Company expenses television and radio advertising costs in the period in which the advertising is first aired and all other advertising costs as incurred. Advertising costs are recorded in marketing and business development and were $212 million, $264 million and $258 million for the years ended December 31, 2020, 2019 and 2018, respectively. Income Taxes Income tax expense is provided for using the asset and liability method, under which deferred tax assets and liabilities are determined based on the temporary differences between the financial reporting and income tax bases of assets and liabilities using currently enacted tax rates. Deferred tax assets are recognized when their realization is determined to be more likely than not. A valuation allowance is provided if the Company believes it is more likely than not that all or some portion of the deferred tax asset will not be realized. An increase or decrease in the valuation allowance that results in a change in circumstances and which causes a change in management’s judgement about the realizability of the related deferred tax asset is included in the current tax provision. Uncertain tax positions are measured at the highest amount of tax benefit for which realization is judged to be more likely than not. Tax benefits that do not meet these criteria are unrecognized tax benefits. The Company recognizes and reports interest and penalties, if necessary, related to uncertain tax positions within its provision for income tax expense. See Note 15: Income Taxes for more information about the Company’s income taxes. Accumulated Other Comprehensive Income The Company records unrealized gains and losses on available-for-sale securities, changes in the fair value of cash flow hedges and certain pension and foreign currency translation adjustments in other comprehensive income (“OCI”) on an after-tax basis where applicable. The Company’s policy is to adjust the tax effects of a component of AOCI in the same period in which the item is sold or otherwise derecognized, or when the carrying value of the item is remeasured. Details of OCI, net of tax, are presented in the statement of comprehensive income and a rollforward of AOCI is presented in the consolidated statements of changes in stockholders’ equity and Note 13: Accumulated Other Comprehensive Income. Significant Revenue Recognition Accounting Policies Loan Interest and Fee Income Interest on loans is comprised largely of interest on credit card loans and is recognized based on the amount of loans outstanding and their contractual interest rate. Interest on credit card loans is included in loan receivables when billed to the customer. The Company accrues unbilled interest revenue each month from a customer’s billing cycle date to the end of the month. The Company applies an estimate of the percentage of loans that will revolve in the next cycle in the estimation of the accrued unbilled portion of interest revenue that is included in accrued interest receivable on the consolidated statements of financial condition. Interest on other loan receivables is accrued each month in accordance with their contractual terms and recorded in accrued interest receivable, which is included in other assets in the consolidated statements of financial condition. The Company recognizes fees (except balance transfer fees and certain product fees) on loan receivables in interest income or loan fee income as the fees are assessed. Balance transfer fees and certain product fees are recognized in interest income or loan fee income ratably over the periods to which they relate. Balance transfer fees are accreted to interest income over the estimated life of the related balance. As of December 31, 2020 and 2019, deferred revenues related to balance transfer fees, recorded as a reduction of loan receivables, were $62 million and $67 million, respectively. Loan fee income consists of fees on credit card loans and includes late, cash advance, returned check and other miscellaneous fees and is reflected net of waivers and charge-offs. Direct loan origination costs on credit card loans are deferred and amortized on a straight-line basis over a one year period and recorded in interest income from credit card loans. Direct loan origination costs on other loan receivables are deferred and amortized over the life of the loan using the interest method and are recorded in interest income from other loans. As of December 31, 2020 and 2019, the remaining unamortized deferred costs related to loan origination were $157 million and $178 million, respectively, and were recorded in loan receivables. The Company accrues interest and fees on loan receivables until the loans are paid or charged off, except in instances of customer bankruptcy, death or fraud, where no further interest and fee accruals occur following notification. Credit card and closed-end consumer loan receivables are placed on non-accrual status upon receipt of notification of the bankruptcy or death of a customer or suspected fraudulent activity on an account. Upon completion of the fraud investigation, non-fraudulent credit card and closed-end consumer loan receivables may resume accruing interest. Payments received on non-accrual loans are allocated according to the same payment hierarchy applied to loans that are accruing interest. When loan receivables are charged off, unpaid accrued interest and fees are reversed against the income line items in which they were originally recorded in the consolidated statements of income. Charge-offs and recoveries of amounts that relate to capitalized interest on private student loans are treated as principal charge-offs and recoveries, affecting the provision for credit losses rather than interest income. The Company considers uncollectible interest and fee revenues in assessing the adequacy of the allowance for credit losses. Interest income from loans accounted for as troubled debt restructurings is accounted for in the same manner as other accruing loans. Cash collections on these loans are allocated according to the same payment hierarchy methodology applied to loans that are not in such programs. Discount and Interchange Revenue The Company earns discount revenue from fees charged to merchants with whom it has entered into card acceptance agreements for processing credit card purchase transactions. The Company earns acquirer interchange revenue primarily from merchant acquirers on Discover Network, Diners Club and PULSE transactions made by credit and debit card customers at merchants with whom merchant acquirers have entered into card acceptance agreements for processing payment card transactions. These card acceptance arrangements generally renew automatically and do not have fixed durations. Under these agreements, the Company stands ready to process payment transactions as and when each is presented. The Company earns discount, interchange and similar fees only when transactions are processed. Contractually defined per-transaction fee amounts typically apply to each type of transaction processed and are recognized as revenue at the time each transaction is captured for settlement. These fees are typically collected by the Company as part of the process of settling transactions daily with merchants and acquirers and are fully earned at the time settlement is made. The Company pays issuer interchange to card-issuing entities that have entered into contractual arrangements to issue cards on the Discover Network and on certain transactions on the Diners Club and PULSE networks. This cost is contractually established and is based on the card-issuing organization’s transaction volume. The Company classifies this cost as a reduction of discount and interchange revenue. Costs of cardholder reward arrangements, including the Cashback Bonus reward program, are classified as reductions of discount and interchange revenue pursuant to guidance under Accounting Standards Codification (“ASC”) Topic 606 governing consideration payable to a customer. For both issuer interchange and cardholder rewards, the Company accrues the cost at the time each underlying card transaction is captured for settlement. Customer Rewards The Company offers its customers various reward programs, including the Cashback Bonus reward program, pursuant to which the Company pays certain customers a reward equal to a percentage of their credit card purchase amounts based on the type and volume of the customer’s purchases. The liability for customer rewards, which is included in accrued expenses and other liabilities on the consolidated statements of financial condition, is recorded on an individual customer basis and is accumulated as qualified customers earn rewards through their ongoing credit card purchase activity or other defined actions. The Company recognizes customer rewards costs as a reduction of the related revenue, if any. In instances where a reward is not associated with a revenue-generating transaction, such as when a reward is given for opening an account, the reward cost is recorded as an operating expense. For the years ended December 31, 2020, 2019 and 2018, rewards costs amounted to $1.9 billion, $1.9 billion and $1.8 billion, respectively. The liability for customer rewards was $1.7 billion at both December 31, 2020 and 2019, and is included in accrued expenses and other liabilities on the consolidated statements of financial condition. Protection Products Revenue The Company earns revenue related to fees received for ancillary products and services, including payment protection and identity theft protection services, to its credit card customers. A portion of this revenue comprises amounts earned for arranging for the delivery of products offered by third-party service providers. The amount of revenue recorded is generally based on either a percentage of a customer’s outstanding balance or a flat fee, in either case assessed monthly and recognized as earned. These contracts are month-to-month arrangements that are cancellable at any time. The Company recognizes each monthly fee in the period to which the service or coverage relates. Transaction Processing Revenue Transaction processing revenue represents switch fees charged to financial institutions and merchants under network

Investments

Investments	12 Months Ended
	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Investments	Investments The Company’s other short-term investments and investment securities consist of the following (dollars in millions): December 31, 2020 2019 United States Treasury bills (1) $ 2,200 $ — Total other short-term investments $ 2,200 $ — United States Treasury securities (2) $ 9,354 $ 9,906 Residential mortgage-backed securities - Agency (3) 560 689 Total investment securities $ 9,914 $ 10,595 (1) Includes United States Treasury bills with maturity dates greater than 90 days but less than one year at the time of acquisition. (2) Includes $117 million and $121 million of United States Treasury securities pledged as swap collateral as of December 31, 2020 and 2019, respectively. (3) Consists of residential mortgage-backed securities issued by Fannie Mae, Freddie Mac and Ginnie Mae. The amortized cost, gross unrealized gains and losses and fair value of available-for-sale and held-to-maturity investment securities are as follows (dollars in millions): Amortized Gross Gross Fair Value At December 31, 2020 Available-for-Sale Investment Securities (1) United States Treasury securities $ 8,987 $ 367 $ — $ 9,354 Residential mortgage-backed securities - Agency 290 10 — 300 Total available-for-sale investment securities $ 9,277 $ 377 $ — $ 9,654 Held-to-Maturity Investment Securities (2) Residential mortgage-backed securities - Agency (3) $ 260 $ 9 $ — $ 269 Total held-to-maturity investment securities $ 260 $ 9 $ — $ 269 At December 31, 2019 Available-for-Sale Investment Securities (1) United States Treasury securities $ 9,759 $ 155 $ (8) $ 9,906 Residential mortgage-backed securities - Agency 414 3 — 417 Total available-for-sale investment securities $ 10,173 $ 158 $ (8) $ 10,323 Held-to-Maturity Investment Securities (2) Residential mortgage-backed securities - Agency (3) $ 272 $ 3 $ (1) $ 274 Total held-to-maturity investment securities $ 272 $ 3 $ (1) $ 274 (1) Available-for-sale investment securities are reported at fair value. (2) Held-to-maturity investment securities are reported at amortized cost. (3) Amounts represent residential mortgage-backed securities that were classified as held-to-maturity as they were entered into as a part of the Company’s community reinvestment initiatives. The Company invests in United States Treasury obligations and residential mortgage-backed securities issued by government agencies, which have long histories with no credit losses and are explicitly or implicitly guaranteed by the United States government. Therefore, management has concluded that there is no expectation of non-payment on its investment securities and does not record an allowance for credit losses on these investments. The following table provides information about investment securities with aggregate gross unrealized losses and the length of time that individual investment securities have been in a continuous unrealized loss position (dollars in millions): Number of Securities in a Loss Position Less than 12 months More than 12 months Fair Unrealized Fair Unrealized At December 31, 2019 Available-for-Sale Investment Securities United States Treasury securities 11 $ 1,402 $ (8) $ — $ — Held-to-Maturity Investment Securities Residential mortgage-backed securities - Agency 58 $ 64 $ — $ 19 $ (1) As of December 31, 2020, there were no investment securities with aggregate gross unrealized losses. There were no proceeds from sales or recognized gains and losses on available-for-sale securities during the years ended December 31, 2020, 2019 and 2018. See Note 13: Accumulated Other Comprehensive Income for unrealized gains and losses on available-for-sale securities during the years ended December 31, 2020, 2019 and 2018. Maturities and weighted-average yields of available-for-sale debt securities and held-to-maturity debt securities are provided in the tables below (dollars in millions): At December 31, 2020 One Year After One After Five After Ten Total Available-for-Sale Investment Securities—Amortized Cost United States Treasury securities $ 2,633 $ 6,354 $ — $ — $ 8,987 Residential mortgage-backed securities - Agency (1) — 45 235 10 290 Total available-for-sale investment securities $ 2,633 $ 6,399 $ 235 $ 10 $ 9,277 Held-to-Maturity Investment Securities—Amortized Cost Residential mortgage-backed securities - Agency (1) $ — $ — $ — $ 260 $ 260 Total held-to-maturity investment securities $ — $ — $ — $ 260 $ 260 Available-for-Sale Investment Securities—Fair Values United States Treasury securities $ 2,661 $ 6,693 $ — $ — $ 9,354 Residential mortgage-backed securities - Agency (1) — 47 243 10 300 Total available-for-sale investment securities $ 2,661 $ 6,740 $ 243 $ 10 $ 9,654 Held-to-Maturity Investment Securities—Fair Values Residential mortgage-backed securities - Agency (1) $ — $ — $ — $ 269 $ 269 Total held-to-maturity investment securities $ — $ — $ — $ 269 $ 269 (1) Maturities of residential mortgage-backed securities are reflective of the contractual maturities of the investment. At December 31, 2020 One Year After One After Five After Ten Total Available-for-Sale Investment Securities—Weighted-Average Yields (1) U.S Treasury securities 1.91 % 2.25 % — % — % 2.15 % Residential mortgage-backed securities - Agency — % 1.62 % 2.07 % 0.99 % 1.97 % Total available-for-sale investment securities 1.91 % 2.24 % 2.07 % 0.99 % 2.14 % Held-to-Maturity Investment Securities—Weighted-Average Yields Residential mortgage-backed securities — % — % — % 3.13 % 3.13 % Total held-to-maturity investment securities — % — % — % 3.13 % 3.13 % (1) The weighted-average yield for available-for-sale investment securities is calculated based on the amortized cost. Taxable interest on investment securities was $252 million, $179 million and $40 million for the years ended December 31, 2020, 2019 and 2018, respectively. There was no tax exempt interest on investment securities for the years ended December 31, 2020, 2019 and 2018. Other Investments As a part of the Company’s community reinvestment initiatives, the Company has made equity investments in certain limited partnerships and limited liability companies that finance the construction and rehabilitation of affordable rental housing, as well as stimulate economic development in low to moderate income communities. These investments are accounted for using the equity method of accounting and are recorded within other assets. The related commitment for future investments is recorded in accrued expenses and other liabilities within the consolidated statements of financial condition. The portion of each investment’s operating results allocable to the Company reduces the carrying value of the investments and is recorded in other expense within the consolidated statements of income. The Company further reduces the carrying value of the investments by recognizing any amounts that are in excess of future net tax benefits in other expense. The Company earns a return primarily through the receipt of tax credits allocated to the affordable housing projects and the community revitalization projects. These investments are not consolidated as the Company does not have a controlling financial interest in the investee entities. As of December 31, 2020 and 2019, the Company had outstanding investments in these entities of $353 million and $336 million, respectively, and related contingent liabilities of $93 million and $74 million, respectively. Of the above outstanding equity investments, the Company had $324 million and $298 million of investments related to affordable housing projects as of December 31, 2020 and 2019, respectively, which had $79 million and $59 million related contingent liabilities, respectively. The Company holds non-controlling equity positions in several payments services entities. Most of these investments are not subject to equity method accounting because the Company does not have significant influence over the investee. The common or preferred equity securities that the Company holds typically do not have readily determinable fair values. As a result, the majority of these investments are carried at cost minus impairment, if any. As of December 31, 2020 and 2019, the carrying value of these investments, which is recorded within other assets on the Company’s consolidated statements of financial condition, was $35 million and $42 million, respectively.

Loan Receivables

Loan Receivables	12 Months Ended
	Dec. 31, 2020
Receivables [Abstract]
Loan Receivables	Loan Receivables The Company has two loan portfolio segments: credit card loans and other loans. The Company’s classes of receivables within the two portfolio segments are depicted in the following table (dollars in millions): December 31, 2020 2019 Credit card loans (1)(2) $ 71,472 $ 77,181 Other loans (3) Private student loans (4) 9,954 9,653 Personal loans 7,177 7,687 Other 1,846 1,373 Total other loans 18,977 18,713 Total loan receivables 90,449 95,894 Allowance for credit losses (5) (8,226) (3,383) Net loan receivables $ 82,223 $ 92,511 (1) Amounts include carrying values of $16.7 billion and $18.9 billion underlying investors’ interest in trust debt at December 31, 2020 and 2019, respectively, and $10.6 billion and $12.7 billion in seller’s interest at December 31, 2020 and 2019, respectively. See Note 5: Credit Card and Student Loan Securitization Activities for additional information. (2) Unbilled accrued interest receivable on credit card loans, which is presented as part of other assets in the Company’s consolidated statements of financial condition, was $420 million and $471 million at December 31, 2020 and 2019, respectively. (3) Accrued interest receivable on private student, personal and other loans, which is presented as part of other assets in the Company’s consolidated statements of financial condition, was $469 million, $49 million and $6 million, respectively, at December 31, 2020 and $461 million, $53 million and $4 million, respectively, at December 31, 2019. (4) Amounts include carrying values of $250 million and $292 million in loans pledged as collateral against the note issued from a student loan securitization trust at December 31, 2020 and 2019, respectively. See Note 5: Credit Card and Student Loan Securitization Activities for additional information. (5) Prior to adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach. Credit Quality Indicators As part of credit risk management activities, on an ongoing basis, the Company reviews information related to the performance of a customer's account with the Company as well as information from credit bureaus, such as FICO or other credit scores, relating to the customer's broader credit performance. Key credit quality indicators that are actively monitored for credit card, private student and personal loans include FICO scores and delinquency status. These indicators are important to understand the overall credit performance of the Company's customers and their ability to repay. FICO scores are generally obtained at origination of the account and are refreshed monthly or quarterly thereafter to assist in predicting customer behavior. Historically, the Company has noted that accounts with FICO scores below 660 have larger delinquencies and credit losses than those with higher credit scores. The following table provides the distribution of the amortized cost basis (excluding accrued interest receivable presented in other assets) by the most recent FICO scores available for the Company's customers for credit card, private student and personal loan receivables (dollars in millions): Credit Risk Profile by FICO Score December 31, 2020 2019 660 and Above Less than 660 660 and Above Less than 660 $ % $ % $ % $ % Credit card loans (1) $ 58,950 82 % $ 12,522 18 % $ 61,997 80 % $ 15,184 20 % Private student loans by origination year (2)(3) 2020 $ 1,173 95 % $ 60 5 % 2019 1,659 96 % 61 4 % $ 1,176 93 % $ 92 7 % 2018 1,365 96 % 61 4 % 1,518 95 % 79 5 % 2017 1,052 95 % 57 5 % 1,198 95 % 69 5 % 2016 797 94 % 47 6 % 934 94 % 58 6 % Prior 3,422 94 % 200 6 % 4,229 93 % 300 7 % Total private student loans $ 9,468 95 % $ 486 5 % $ 9,055 94 % $ 598 6 % Personal loans by origination year 2020 $ 2,880 99 % $ 25 1 % 2019 2,183 96 % 90 4 % $ 3,529 98 % $ 62 2 % 2018 1,018 92 % 90 8 % 1,941 93 % 140 7 % 2017 558 89 % 69 11 % 1,167 90 % 136 10 % 2016 189 87 % 28 13 % 475 88 % 65 12 % Prior 38 81 % 9 19 % 145 84 % 27 16 % Total personal loans $ 6,866 96 % $ 311 4 % $ 7,257 94 % $ 430 6 % (1) Amounts include $1.0 billion and $956 million of revolving line-of-credit arrangements that were converted to term loans as a result of a TDR program as of December 31, 2020 and 2019, respectively. (2) A majority of student loan originations occur in the third quarter and disbursements can span multiple calendar years. (3) FICO score represents the higher credit score of the cosigner or borrower. Delinquencies are an indicator of credit quality at a point in time. A loan balance is considered delinquent when contractual payments on the loan become 30 days past due. The amortized cost basis (excluding accrued interest receivable presented in other assets) of delinquent loans in the Company’s loan portfolio is shown below for credit card, private student and personal loan receivables (dollars in millions): December 31, 2020 2019 30-89 Days 90 or Total Past 30-89 Days 90 or Total Past Credit card loans $ 739 $ 739 $ 1,478 $ 999 $ 1,020 $ 2,019 Private student loans by origination year (1)(2) 2020 $ — $ — $ — 2019 3 1 4 $ — $ — $ — 2018 9 3 12 4 1 5 2017 12 4 16 11 3 14 2016 14 3 17 14 5 19 Prior 72 17 89 106 37 143 Total private student loans $ 110 $ 28 $ 138 $ 135 $ 46 $ 181 Personal loans by origination year 2020 $ 5 $ 2 $ 7 2019 18 9 27 $ 11 $ 3 $ 14 2018 15 7 22 27 11 38 2017 10 5 15 22 10 32 2016 4 1 5 10 5 15 Prior 1 1 2 4 2 6 Total personal loans $ 53 $ 25 $ 78 $ 74 $ 31 $ 105 (1) Student loans may include a deferment period, during which customers are not required to make payments while enrolled in school at least half time as determined by the school. During a deferment period, these loans do not advance into delinquency. (2) Includes PCD loans for all periods presented. In response to the COVID-19 pandemic, the Company expanded borrower relief offerings to include Skip-a-Pay (payment deferral) and other loan modification programs, complementing the assistance already available through existing loan modification programs. The accounts using these modifications as a result of the COVID-19 pandemic impact were evaluated for potential exclusion from TDR status either due to the insignificance of the concession or because they qualified for exemption pursuant to the CARES Act. The Skip-a-Pay (payment deferral) programs allowed customers on a monthly or other periodic basis to request approval to skip their payment(s) for that month or period. The utilization of these Skip-a-Pay (payment deferral) programs had a favorable impact on reported credit performance because, pursuant to regulatory guidelines, accounts enrolled in the Skip-a-Pay (payment deferral) programs did not advance through delinquency cycles in the same time frame as would have occurred without the Skip-a-Pay (payment deferral) programs. Specifically, current accounts enrolled in the Skip-a-Pay (payment deferral) programs did not advance to delinquency and delinquent accounts enrolled in the Skip-a-Pay (payment deferral) programs did not advance to the next delinquency cycle or to charge-off. The Skip-a-Pay (payment deferral) programs provided only an insignificant delay in payment on the enrolled accounts or loans and therefore those deferrals were not classified as TDRs. While the Company continues to support and provide assistance to all customers impacted by the COVID-19 pandemic, the Company is no longer offering new enrollments in the Skip-a-Pay (payment deferral) programs or other loan modifications developed specifically for COVID-19 as of August 31, 2020. By the fourth quarter of 2020, there was no material impact to delinquencies from these payment deferrals since delinquent loans were advancing through the delinquency cycles or to charge-off as appropriate after these payment deferrals ceased being offered. Allowance for Credit Losses The following tables provide changes in the Company’s allowance for credit losses (dollars in millions): For the Year Ended December 31, 2020 Credit Card Loans Private Student Personal Loans Other Loans Total Balance at December 31, 2019 (1) $ 2,883 $ 148 $ 348 $ 4 $ 3,383 Cumulative effect of ASU No. 2016-13 adoption (2) 1,667 505 265 24 2,461 Balance at January 1, 2020 4,550 653 613 28 5,844 Additions Provision for credit losses (3) 4,379 251 476 11 5,117 Deductions Charge-offs (3,101) (85) (289) (1) (3,476) Recoveries 663 21 57 — 741 Net charge-offs (2,438) (64) (232) (1) (2,735) Balance at December 31, 2020 $ 6,491 $ 840 $ 857 $ 38 $ 8,226 For the Year Ended December 31, 2019 Credit Card Loans Private Student Personal Loans Other Loans Total Balance at December 31, 2018 (1) $ 2,528 $ 169 $ 338 $ 6 $ 3,041 Additions Provision for credit losses (1) 2,849 51 332 (1) 3,231 Deductions Charge-offs (3,165) (82) (369) (1) (3,617) Recoveries 671 13 47 — 731 Net charge-offs (4) (2,494) (69) (322) (1) (2,886) Other (5) — (3) — — (3) Balance at December 31, 2019 (1) $ 2,883 $ 148 $ 348 $ 4 $ 3,383 For the Year Ended December 31, 2018 Credit Card Loans Private Student Personal Loans Other Loans Total Balance at December 31, 2017 (1) $ 2,147 $ 162 $ 301 $ 11 $ 2,621 Additions Provision for credit losses (1) 2,594 95 345 1 3,035 Deductions Charge-offs (2,734) (97) (345) (6) (3,182) Recoveries 521 12 37 — 570 Net charge-offs (4) (2,213) (85) (308) (6) (2,612) Other (5) — (3) — — (3) Balance at December 31, 2018 (1) $ 2,528 $ 169 $ 338 $ 6 $ 3,041 (1) Prior to the adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach. (2) Represents the adjustment to the allowance for credit losses as a result of the adoption of ASU No. 2016-13 on January 1, 2020. (3) Excludes a $17 million build of the liability for expected credit losses on unfunded commitments for the year ended December 31, 2020, as the liability is recorded in accrued expenses and other liabilities in the Company’s consolidated statements of financial condition. (4) Prior to the 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. (5) 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). The allowance for credit losses was $8.2 billion at December 31, 2020, which reflects a $4.8 billion build over the amount of the allowance for credit losses at December 31, 2019. The allowance build across all loan products was due to (i) a $2.5 billion cumulative-effect adjustment for the adoption of CECL on January 1, 2020, and (ii) a $2.3 billion build that primarily reflects an economic outlook that included the COVID-19 pandemic and resulting economic stress. In estimating the allowance at December 31, 2020, the Company used a macroeconomic forecast that projected (i) a peak unemployment rate of 8.7%, recovering to 8.2% by the end of 2021 with slow recovery over the next few years and (ii) a 2.7% growth in gross domestic product in 2021. The Company also considered the uncertainties associated with some of the assumptions used in the macroeconomic forecast, including the amount and timing of additional government stimulus. Furthermore, the estimate contemplated the impact of previous government stimulus programs and other company-initiated loan modification programs on borrower payment trends. The impact of the COVID-19 pandemic on the economy continues to cause uncertainty in assumptions surrounding factors such as length and depth of economic stresses and longer term impacts on borrower behavior, which has required significant management judgment in estimating the allowance for credit losses. Company-initiated loan modification programs include those offered specifically in response to the COVID-19 pandemic as well as existing programs offered to customers experiencing difficulty making their payments. In addition to Skip-a-Pay (payment deferral) programs, which ended on August 31, 2020, the Company has other modification programs that customers have utilized during the period related to the pandemic. The accounts using these modifications as a result of the pandemic impact were evaluated for potential exclusion from TDR status either due to the insignificance of the concession or because they qualified for exemption under the CARES Act. The effects of all loan modifications, including TDRs, loan modifications exempt from TDR status under the CARES Act and Skip-a-Pay (payment deferral) programs, are considered as part of the process for determining the estimate of expected loss reflected in the allowance for credit losses. The forecast period management deemed to be reasonable and supportable was 18 months for all periods since the adoption of CECL except for the estimate as of March 31, 2020. The decrease to 12 months as of March 31, 2020, was due to the uncertainty caused by the rapidly changing economic environment resulting from the COVID-19 pandemic. The return to an 18-month reasonable and supportable forecast period was based on the view that the present macroeconomic conditions will last for a longer period than previously expected. The reversion period was 12 months for all quarters since the adoption of CECL. During the first quarter of 2020, a straight-line method was used to revert to appropriate historical information. In the second quarter of 2020, the high degree of economic stress led the Company to apply a weighted reversion method for credit card loans that puts more emphasis on the loss forecast model rather than lower historical losses. For similar reasons, the Company determined it was appropriate to apply a weighted reversion method for all loans in the third and fourth quarter. The net charge-offs on credit card loans for the year ended December 31, 2020, decreased when compared to the year ended December 31, 2019, due to decreased loan receivables, government stimulus and disaster relief programs. The net charge-offs on private loans for the year ended December 31, 2020, decreased when compared to the year ended December 31, 2019, due to the impacts of government stimulus and disaster relief programs. The net charge-offs on personal loans for the year ended December 31, 2020, decreased when compared to the year ended December 31, 2019, due to improved underwriting, government stimulus and disaster relief programs. The net charge-offs on other loans for the year ended December 31, 2020, remained flat when compared to the same period in 2019. Net charge-offs of principal are recorded against the allowance for credit losses, as shown in the preceding table. Information regarding net charge-offs of interest and fee revenues on credit card and other loans is as follows (dollars in millions): For the Years Ended December 31, 2020 2019 2018 Interest and fees accrued subsequently charged off, net of recoveries (recorded as a reduction of interest income) $ 484 $ 515 $ 442 Fees accrued subsequently charged off, net of recoveries (recorded as a reduction to other income) $ 117 $ 123 $ 109 Delinquent and Non-Accruing Loans The amortized cost basis (excluding accrued interest receivable presented in other assets) of delinquent and non-accruing loans in the Company’s loan portfolio is shown below for each class of loan receivables (dollars in millions): 30-89 Days 90 or Total Past 90 or Total Non-accruing (1) At December 31, 2020 Credit card loans $ 739 $ 739 $ 1,478 $ 687 $ 209 Other loans Private student loans (2) 110 28 138 27 12 Personal loans 53 25 78 23 12 Other 8 3 11 — 10 Total other loans 171 56 227 50 34 Total loan receivables $ 910 $ 795 $ 1,705 $ 737 $ 243 At December 31, 2019 Credit card loans $ 999 $ 1,020 $ 2,019 $ 940 $ 237 Other loans Private student loans (2) 135 46 181 45 11 Personal loans 74 31 105 29 12 Other 5 2 7 — 6 Total other loans 214 79 293 74 29 Total loan receivables $ 1,213 $ 1,099 $ 2,312 $ 1,014 $ 266 (1) The Company estimates that the gross interest income that would have been recorded in accordance with the original terms of non-accruing credit card loans was $33 million, $45 million and $41 million for the years ended December 31, 2020, 2019 and 2018, respectively. The Company does not separately track the amount of gross interest income that would have been recorded in accordance with the original terms of loans. This amount was estimated based on customers’ current balances and most recent interest rates. (2) Includes PCD loans for all periods presented. Troubled Debt Restructurings The Company has internal loan modification programs that provide relief to credit card, student and personal loan borrowers who may be experiencing financial hardship. The Company considers a modified loan in which a concession has been granted to the borrower to be a TDR based on the cumulative length of the concession period and credit quality of the borrower. New programs are evaluated to determine which of them meet the definition of a TDR, including modification programs provided to customers for temporary relief due to the economic impacts of the COVID-19 pandemic. The internal loan modification programs include both temporary and permanent programs, which vary by product. External loan modification programs are also available for credit card and personal loans. For all temporary modification programs, including those created specifically in response to the COVID-19 pandemic, the modified loans are evaluated for potential exclusion from TDR status either due to the insignificance of the concession or because they qualify for exemption pursuant to the CARES Act. To the extent the accounts do not meet the requirements for exclusion, temporary and permanent modifications on credit card and personal loans, as well as temporary modifications on student loans and certain grants of student loan forbearance, result in the loans being classified as TDRs. In addition, loans that defaulted (see table on loans that defaulted from a TDR program that follows) or graduated from modification programs or forbearance continue to be classified as TDRs, except as noted below. For credit card customers, the Company offers both temporary and permanent hardship programs. The temporary hardship programs consist of an interest rate reduction and in some cases a reduced minimum payment, both lasting for a period no longer than 12 months. Charging privileges on these accounts are generally suspended while in the program and if certain criteria are met, may be reinstated following completion of the program. Beginning in 2020, credit card accounts of borrowers that have previously participated in a temporary interest rate reduction program and that have both demonstrated financial stability and had their charging privileges reinstated at a market-based interest rate, are excluded from the balance of TDRs. The permanent modification program involves closing the account, changing the structure of the loan to a fixed payment loan with a maturity no longer than 60 months and reducing the interest rate on the loan. The permanent modification program does not normally provide for the forgiveness of unpaid principal, but may allow for the reversal of certain unpaid interest or fee assessments. The Company also makes permanent loan modifications for customers who request financial assistance through external sources, such as a consumer credit counseling agency program. These loans typically receive a reduced interest rate but continue to be subject to the original minimum payment terms and do not normally include waiver of unpaid principal, interest or fees. These loans remain in the population of TDRs until they are paid off or charged off. At December 31, 2020 and 2019, there were $5.7 billion and $5.6 billion, respectively, of private student loans in repayment and $117 million and $46 million, respectively, in forbearance. To assist student loan borrowers who are experiencing temporary financial difficulties but are willing to resume making payments, the Company may offer hardship forbearance or programs that include payment deferral, temporary payment reduction, temporary interest rate reduction or extended terms. A modified loan typically meets the definition of a TDR based on the cumulative length of the concession period and a determination of financial distress based on an evaluation of the credit quality of the borrower using FICO scores. For personal loan customers, in certain situations the Company offers various payment programs, including temporary and permanent programs. The temporary programs normally consist of a reduction of the minimum payment for a period of no longer than 12 months with the option of a final balloon payment required at the end of the loan term or an extension of the maturity date with the total term not exceeding nine years. Further, in certain circumstances the interest rate on the loan is reduced. The permanent programs involve changing the terms of the loan in order to pay off the outstanding balance over a longer term and in certain circumstances reducing the interest rate on the loan. Similar to the temporary programs, the total term may not exceed nine years. The Company also allows permanent loan modifications for customers who request financial assistance through external sources, similar to the credit card customers discussed above. Payments are modified based on the new terms agreed upon with the credit counseling agency. Personal loans included in temporary and permanent programs are classified as TDRs. Borrower performance after using payment programs or forbearance is monitored. The Company believes the programs are useful in assisting customers experiencing financial difficulties and allowing them to make timely payments. In addition to helping customers with their credit needs, these programs are designed to maximize collections and ultimately the Company’s profitability. The Company plans to continue to use payment programs and forbearance as a means to provide relief to customers experiencing temporary financial difficulties and, as a result, expects to have additional loans classified as TDRs in the future. In order to evaluate the primary financial effects that resulted from credit card loans entering into a TDR program during the years ended December 31, 2020, 2019 and 2018, the Company quantified the amount by which interest and fees were reduced during the periods. During the years ended December 31, 2020, 2019 and 2018, the Company forgave approximately $66 million, $73 million and $48 million, respectively, of interest and fees as a result of accounts entering into a credit card loan TDR program. For all loan products, interest income on modified loans is recognized based on the modified contractual terms. TDR program balances and number of accounts have been favorably impacted by the exclusion of certain modifications from the TDR designation in accordance with the CARES Act and are lower than they otherwise would have been. The Omnibus and COVID Relief and Response Act extended the loan modification relief provided by the CARES Act through the earlier of January 1, 2022, or the date that is 60 days after the termination of the national emergency declared by the President of the United States of America on March 13, 2020, under the National Emergencies Act related to the outbreak of COVID-19. As such, reported TDRs are expected to remain lower than they otherwise would have been. The following table provides information on loans that entered a TDR program during the period (dollars in millions): For the Years Ended December 31, 2020 2019 2018 Number of Accounts Balances Number of Accounts Balances Number of Accounts Balances Accounts that entered a TDR program during the period Credit card loans (1) 152,055 $ 1,022 368,009 $ 2,364 268,817 $ 1,713 Private student loans 1,916 $ 35 6,742 $ 124 4,057 $ 74 Personal loans 8,805 $ 114 10,945 $ 147 8,260 $ 111 (1) Accounts that entered a credit card TDR program include $670 million, $741 million and $491 million that were converted from revolving line-of-credit arrangements to term loans during the years ended December 31, 2020, 2019 and 2018, respectively. The following table presents the carrying value of loans that experienced a payment default during the period that had been modified in a TDR during the 15 months preceding the end of each period (dollars in millions): For the Years Ended December 31, 2020 2019 2018 Number of Accounts Aggregated Outstanding Balances Upon Default Number of Accounts Aggregated Outstanding Balances Upon Default Number of Accounts Aggregated Outstanding Balances Upon Default Troubled debt restructurings that subsequently defaulted Credit card loans (1)(2) 48,075 $ 276 71,326 $ 410 42,659 $ 239 Private student loans (3) 1,119 $ 22 1,406 $ 27 1,041 $ 19 Personal loans (2) 3,145 $ 46 4,152 $ 59 2,955 $ 40 (1) Terms revert back to the pre-modification terms for customers who default from a temporary program and charging privileges remain suspended in most cases. (2) For credit card loans and personal loans, a customer defaults from a modification program either after two consecutive missed payments or at charge-off, depending on the program. The outstanding balance upon default is generally the loan balance at the end of the month prior to default. (3) For student loans, defaults have been defined as loans that are 60 or more days delinquent. The outstanding balance upon default is generally the loan balance at the end of the month prior to default. Of the account balances that defaulted as shown above for the years ended December 31, 2020, 2019 and 2018, approximately 53%, 38% and 36%, respectively, of the total balances were charged off at the end of the month in which they defaulted from a TDR program. For accounts that have defaulted from a TDR program and have not been subsequently charged off, the balances are included in the allowance for credit loss analysis discussed above under “— Allowance for Credit Losses.” Geographical Distribution of Loans The Company originates credit card loans throughout the United States. The geographic distribution of the Company’s credit card loan receivables was as follows (dollars in millions): December 31, 2020 2019 $ % $ % California $ 6,273 8.8 % $ 7,110 9.2 % Texas 6,182 8.6 6,543 8.5 Florida 4,931 6.9 5,176 6.7 New York 4,836 6.8 5,335 6.9 Illinois 3,714 5.2 4,084 5.3 Pennsylvania 3,616 5.1 3,873 5.0 Ohio 3,005 4.2 3,207 4.2 New Jersey 2,558 3.6 2,807 3.6 Georgia 2,204 3.1 2,325 3.0 Michigan 1,983 2.8 2,165 2.8 Other 32,170 44.9 34,556 44.8 Total credit card loans $ 71,472 100 % $ 77,181 100 % The Company originates private student, personal and other loans throughout the United States. The geographic distribution of private student, personal and other loan receivables was as follows (dollars in millions): December 31, 2020 2019 $ % $ % New York $ 1,797 9.5 % $ 1,859 9.9 % California 1,706 9.0 1,764 9.4 Pennsylvania 1,317 6.9 1,275 6.8 Texas 1,224 6.4 1,151 6.2 Illinois 1,163 6.1 1,157 6.2 New Jersey 1,002 5.3 980 5.2 Florida 975 5.1 930 5.0 Ohio 758 4.0 739 4.0 Massachusetts 588 3.1 594 3.2 Michigan 585 3.1 585 3.1 Other 7,862 41.5 7,679 41.0 Total other loans $ 18,977 100 % $ 18,713 100 %

Credit Card and Student Loan Se

Credit Card and Student Loan Securitization Activities	12 Months Ended
	Dec. 31, 2020
Variable Interest Entities Disclosure [Abstract]
Credit Card and Student Loan Securitization Activities	Credit Card and Student Loan Securitization Activities The Company’s securitizations are accounted for as secured borrowings and the related trusts are treated as consolidated subsidiaries of the Company. For a description of the Company’s principles of consolidation with respect to VIEs, see Note 1: Background and Basis of Presentation. Credit Card Securitization Activities The Company accesses the term asset securitization market through DCMT and DCENT. Credit card loan receivables are transferred into DCMT and beneficial interests in DCMT are transferred into DCENT. DCENT issues debt securities to investors that are reported in long-term borrowings. The DCENT debt structure consists of four classes of securities (DiscoverSeries Class A, B, C and D notes), with the most senior class generally receiving a triple-A rating. In order to issue senior, higher rated classes of notes, it is necessary to obtain the appropriate amount of credit enhancement, generally through the issuance of junior, lower rated or more highly subordinated classes of notes. The subordinated classes are held by wholly-owned subsidiaries of Discover Bank. The Company is exposed to credit-related risk of loss associated with trust assets as of the balance sheet date through the retention of these subordinated interests. The current expected credit loss on trust assets is included in the allowance for credit losses estimate. The Company’s retained interests in the assets of the trusts, consisting of investments in DCENT notes held by subsidiaries of Discover Bank, constitute intercompany positions, which are eliminated in the preparation of the Company’s consolidated statements of financial condition. Upon transfer of credit card loan receivables to the trust, the receivables and certain cash flows derived from them become restricted for use in meeting obligations to the trusts’ creditors. Further, the transferred credit card loan receivables are owned by the trust and are not available to third-party creditors of the Company. The trusts have ownership of cash balances, the amounts of which are reported in restricted cash. With the exception of the seller’s interest in trust receivables, the Company’s interests in trust assets are generally subordinate to the interests of third-party investors and, as such, may not be realized by the Company if needed to absorb deficiencies in cash flows that are allocated to the investors in the trusts’ debt. Apart from the restricted assets related to securitization activities, the investors and the securitization trusts have no recourse to the Company’s other assets or the Company’s general credit for a shortage in cash flows. The carrying values of these restricted assets, which are presented on the Company’s consolidated statements of financial condition as relating to securitization activities, are shown in the following table (dollars in millions): December 31, 2020 2019 Restricted cash $ 16 $ 28 Investors’ interests held by third-party investors 10,600 14,100 Investors’ interests held by wholly-owned subsidiaries of Discover Bank 6,121 4,796 Seller’s interest 10,575 12,652 Loan receivables (1) 27,296 31,548 Allowance for credit losses allocated to securitized loan receivables (1)(2) (1,936) (1,179) Net loan receivables 25,360 30,369 Other 3 5 Carrying value of assets of consolidated variable interest entities $ 25,379 $ 30,402 (1) The Company maintains its allowance for credit losses at an amount equal to lifetime expected credit losses associated with all loan receivables, which includes all loan receivables in the trusts. Therefore, credit risk associated with the transferred receivables is fully reflected on the Company’s balance sheet in accordance with GAAP. (2) Prior to the adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach. The debt securities issued by the consolidated trusts are subject to credit, payment and interest rate risks on the transferred credit card loan receivables. To protect investors in the securities, there are certain features or triggering events that could cause an early amortization of the debt securities, including triggers related to the impact of the performance of the trust receivables on the availability and adequacy of cash flows to meet contractual requirements. As of December 31, 2020, no economic or other early amortization events have occurred. The Company continues to own and service the accounts that generate the loan receivables held by the trusts. Discover Bank receives servicing fees from the trusts based on a percentage of the monthly investor principal balance outstanding. Although the fee income to Discover Bank offsets the fee expense to the trusts and thus is eliminated in consolidation, failure to service the transferred loan receivables in accordance with contractual requirements could lead to a termination of the servicing rights and the loss of future servicing income, net of related expenses. Student Loan Securitization Activities Private student loan trust receivables are reported in loan receivables and the related debt issued by the trust is reported in long-term borrowings. The assets of the trust are restricted from being sold or pledged as collateral for other borrowings and the cash flows from these restricted assets may be used only to pay obligations of the trust. With the exception of the trust’s restricted assets, the trust and investors have no recourse to the Company’s other assets or the Company’s general credit for a shortage in cash flows. Principal payments on the long-term secured borrowings are made as cash is collected on the underlying loans that are collateral on the secured borrowings. The Company does not have access to cash collected by the securitization trust until cash is released in accordance with the trust indenture agreement. Similar to the credit card securitizations, the Company continues to own and service the student loan receivables held by the trust and receives servicing fees from the trust based on a percentage of the principal balance outstanding. Although the servicing fee income offsets the fee expense related to the trust and thus is eliminated in consolidation, failure to service the transferred loan receivables in accordance with contractual requirements could lead to a termination of the servicing rights and the loss of future servicing income, net of related expenses. Under terms of the trust arrangement, the Company has the option, but not the obligation, to provide financial support to the trust, but has never provided such support. A substantial portion of the credit risk associated with the securitized loans has been transferred to a third party under an indemnification arrangement. The carrying values of these restricted assets, which are presented on the Company’s consolidated statements of financial condition as relating to securitization activities, are shown in the following table (dollars in millions): December 31, 2020 2019 Restricted cash $ 9 $ 12 Student loan receivables 250 292 Carrying value of assets of consolidated variable interest entities $ 259 $ 304

Premises and Equipment

Premises and Equipment	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Premises and Equipment	Premises and Equipment A summary of premises and equipment, net is as follows (dollars in millions): December 31, 2020 2019 Land $ 38 $ 42 Buildings and improvements 673 693 Furniture, fixtures and equipment 1,125 1,082 Software 901 851 Premises and equipment 2,737 2,668 Less: accumulated depreciation (1,349) (1,276) Less: accumulated amortization of software (361) (335) Premises and equipment, net $ 1,027 $ 1,057

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill As of December 31, 2020 and 2019, the Company had goodwill of $255 million related to PULSE, which is part of the Payment Services segment. The Company conducted its annual goodwill impairment test as of October 1, 2020 and 2019 and no impairment charges were identified. Intangible Assets The Company’s amortizable intangible assets consisting of customer relationships and trade names resulted from various acquisitions and are primarily included in the Payment Services segment. Non-amortizable intangible assets consist primarily of trade name intangibles and international transaction processing rights included in the Payment Services segment. In the second quarter of 2020, the Company conducted an interim impairment test on its Diners Club trade names and international transaction processing rights non-amortizable intangible assets, due to changes in the international travel and entertainment businesses and a declining revenue outlook for the foreseeable future resulting from the COVID-19 pandemic. The valuation methodology used to value the trade names and international transaction processing rights was based on a discounted cash flow method, consistent with the methodology used for annual impairment testing. As a result of this analysis, the Company determined that the trade names and international transaction processing rights were impaired and recognized a charge in its Payment Services segment of $36 million and $23 million, respectively. The impairment was recorded in other expense on the consolidated statements of income. As of December 31, 2020, the trade names have a remaining net book value of $92 million and the international transaction processing rights have no remaining net book value. The Company conducted its annual impairment test of non-amortizable intangible assets as of October 1, 2020 and 2019 and no additional material impairment charges were identified. The following table summarizes the Company’s intangible assets (dollars in millions): December 31, 2020 2019 Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net Amortizable intangible assets Customer relationships $ 69 $ 69 $ — $ 69 $ 68 $ 1 Trade name and other 8 5 3 8 5 3 Total amortizable intangible assets 77 74 3 77 73 4 Non-amortizable intangible assets Trade names 92 — 92 128 — 128 International transaction processing rights — — — 23 — 23 Total non-amortizable intangible assets 92 — 92 151 — 151 Total intangible assets $ 169 $ 74 $ 95 $ 228 $ 73 $ 155 Amortization expense related to the Company’s intangible assets was not material for the years ended December 31, 2020, 2019 and 2018 and the expected amortization expense for the next five years based on intangible assets at the end of the current period is not material, either individually or in the aggregate.

Deposits

Deposits	12 Months Ended
	Dec. 31, 2020
Deposits [Abstract]
Deposits	Deposits The Company offers its deposit products to customers through two channels: (i) through direct marketing, internet origination and affinity relationships (“direct-to-consumer deposits”) and (ii) indirectly through contractual arrangements with securities brokerage firms (“brokered deposits”). Direct-to-consumer deposits include online savings accounts, certificates of deposit, money market accounts, IRA certificates of deposit and checking accounts, while brokered deposits include certificates of deposit and sweep accounts. The following table provides a summary of interest-bearing deposit accounts (dollars in millions): December 31, 2020 2019 Certificates of deposit in amounts less than $100,000 $ 19,105 $ 25,113 Certificates of deposit in amounts $100,000 or greater (1) 9,164 9,268 Savings deposits, including money market deposit accounts 47,426 37,574 Total interest-bearing deposits $ 75,695 $ 71,955 (1) Includes $2.6 billion in certificates of deposit equal to or greater than $250,000, the Federal Deposit Insurance Corporation (“FDIC”) insurance limit, as of December 31, 2020 and 2019. The following table summarizes certificates of deposit in amounts of $100,000 or greater by contractual maturity (dollars in millions): December 31, 2020 Three months or less $ 2,461 Over three months through six months 1,669 Over six months through twelve months 2,883 Over twelve months 2,151 Total $ 9,164 The following table summarizes certificates of deposit maturing over each of the next five years and thereafter (dollars in millions): December 31, 2020 2021 $ 17,850 2022 4,520 2023 2,259 2024 1,363 2025 866 Thereafter 1,411 Total $ 28,269

Long-Term Borrowings

Long-Term Borrowings	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Long-Term Borrowings	Long-Term Borrowings Long-term borrowings consist of borrowings having original maturities of one year or more. The following table provides a summary of the Company’s long-term borrowings and weighted-average interest rates on outstanding balances (dollars in millions): December 31, 2020 December 31, 2019 Maturity Interest Weighted-Average Interest Rate Outstanding Amount Outstanding Amount Securitized Debt Fixed-rate asset-backed securities (1) 2021-2024 1.85% - 3.32% 2.74% $ 6,041 $ 8,609 Floating-rate asset-backed securities (2)(3) 2021-2024 0.39% - 0.76% 0.56% 4,669 5,515 Total Discover Card Master Trust I and Discover Card Execution Note Trust 10,710 14,124 Floating-rate asset-backed security (4)(5) 2031 4.25% 4.25% 130 160 Total student loan securitization trust 130 160 Total long-term borrowings - owed to securitization investors 10,840 14,284 Discover Financial Services (Parent Company) Fixed-rate senior notes 2022-2027 3.75% - 5.20% 4.16% 3,337 3,296 Fixed-rate retail notes 2021-2031 2.85% - 4.60% 3.73% 336 340 Discover Bank Fixed-rate senior bank notes (1) 2021-2030 2.45% - 4.65% 3.57% 6,213 6,785 Fixed-rate subordinated bank notes (1) 2028 4.68% 4.68% 515 996 Total long-term borrowings $ 21,241 $ 25,701 (1) The Company uses interest rate swaps to hedge portions of these long-term borrowings against changes in fair value attributable to changes in London Interbank Offered Rate (“LIBOR”) or Overnight Index Swap (“OIS”) Rate. Use of these interest rate swaps impacts carrying value of the debt. See Note 21: Derivatives and Hedging Activities. (2) Discover Card Execution Note Trust floating-rate asset-backed securities include issuances with the following interest rate terms: 1-month LIBOR + 23 to 60 basis points as of December 31, 2020. (3) The Company uses interest rate swaps to manage its exposure to changes in interest rates related to future cash flows resulting from interest payments on a portion of these long-term borrowings. There is no impact on debt carrying value from use of these interest rate swaps. See Note 21: Derivatives and Hedging Activities. (4) The student loan securitization trust floating-rate asset-backed security includes an issuance with the following interest rate term: Prime rate + 100 basis points as of December 31, 2020. (5) Repayment of this debt is dependent upon the timing of principal and interest payments on the underlying student loans. The date shown represents final maturity date. The following table summarizes long-term borrowings maturing over each of the next five years and thereafter (dollars in millions): Amount 2021 $ 4,217 2022 5,201 2023 3,402 2024 2,625 2025 533 Thereafter 5,263 Total $ 21,241 The Company has access to committed borrowing capacity through private securitizations to support the funding of its credit card loan receivables. As of December 31, 2020, the total commitment of secured credit facilities through private providers was $6.0 billion, none of which was drawn at December 31, 2020. Access to the unused portions of the secured credit facilities is subject to the terms of the agreements with each of the providers, which have various

Stock-Based Compensation Plans

Stock-Based Compensation Plans	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation Plans	Stock-Based Compensation Plans The Company has two stock-based compensation plans: the Discover Financial Services Omnibus Incentive Plan (“Omnibus Plan”) and the Discover Financial Services Directors’ Compensation Plan (“Directors’ Compensation Plan”). Omnibus Plan The Omnibus Plan, which is stockholder approved, provides for the award of stock options, stock appreciation rights, restricted stock, restricted stock units (“RSUs”), performance stock units (“PSUs”) and other stock-based and/or cash awards (collectively, “awards”). Currently, the Company does not have any stock options, stock appreciation rights or restricted stock outstanding. The total number of shares that may be granted is 45 million shares, subject to adjustments for certain transactions as described in the Omnibus Plan document. Shares granted under the Omnibus Plan may be the following: (i) authorized but unissued shares and (ii) treasury shares that the Company acquires in the open market, in private transactions or otherwise. Directors’ Compensation Plan The Directors’ Compensation Plan, which is stockholder approved, permits the grant of RSUs to non-employee directors. Under the Directors’ Compensation Plan, the Company may issue awards of up to a total of 1 million shares of common stock to non-employee directors. Shares of stock that are issuable pursuant to the awards granted under the Directors’ Compensation Plan may be authorized but unissued shares, treasury shares or shares that the Company acquires in the open market. Annual awards for eligible directors are calculated by dividing $150 thousand by the fair market value of a share of stock on the date of grant and are subject to a restriction period whereby 100% of such units shall vest in full on the earlier of the one year anniversary of the date of grant or immediately prior to the first annual meeting of shareholders following the date of grant. RSUs include the right to receive dividend equivalents in the same amount and at the same time as dividends paid to all Company common shareholders. Stock-Based Compensation The following table details the compensation cost, net of forfeitures (dollars in millions): For the Years Ended December 31, 2020 2019 2018 RSUs $ 49 $ 49 $ 49 PSUs (1) (8) 20 32 Total stock-based compensation expense $ 41 $ 69 $ 81 Income tax benefit $ 9 $ 12 $ 15 (1) Total PSU expense for the year ended December 31, 2020, includes an incremental $2.4 million representing a modification to the 2018 PSU award. The nature of the modification was to adjust the payout to compensate for the 2020 CECL adoption impact on EPS. RSUs The following table sets forth the activity related to vested and unvested RSUs: Number of Units Weighted-Average Remaining Contractual Term (in years) Aggregate RSUs at December 31, 2019 2,148,976 $ 182 Granted 631,692 Conversions to common stock (769,525) Forfeited (76,744) RSUs at December 31, 2020 1,934,399 0.83 $ 175 Vested and convertible RSUs at December 31, 2020 728,787 0.00 $ 66 The following table sets forth the activity related to unvested RSUs: Number of Units Weighted-Average Grant-Date Fair Value Unvested RSUs at December 31, 2019 1) 1,104,562 $ 72.33 Granted 631,692 $ 76.58 Vested (705,427) $ 72.56 Forfeited (76,744) $ 77.19 Unvested RSUs at December 31, 2020 (1) 954,083 $ 74.58 (1) Unvested RSUs represent awards where recipients have yet to satisfy either explicit vesting terms or retirement-eligibility requirements. Compensation cost associated with RSUs is determined based on the number of units granted and the fair value on the date of grant. The fair value is amortized on a straight-line basis, net of estimated forfeitures over the requisite service period for each separately vesting tranche of the award. The requisite service period is generally the vesting period. The following table summarizes the total intrinsic value of the RSUs converted to common stock and the total grant-date fair value of RSUs vested (dollars in millions, except weighted-average grant-date fair value amounts): For the Years Ended December 31, 2020 2019 2018 Intrinsic value of RSUs converted to common stock $ 55 $ 93 $ 67 Grant-date fair value of RSUs vested $ 51 $ 48 $ 54 Weighted-average grant-date fair value of RSUs granted $ 76.58 $ 73.52 $ 77.53 As of December 31, 2020, there was $23 million of total unrecognized compensation cost related to non-vested RSUs. The cost is expected to be recognized over a weighted-average period of 0.84 years. RSUs provide for accelerated vesting if there is a change in control or upon certain terminations (as defined in the Omnibus Plan or the award certificate). RSUs include the right to receive dividend equivalents in the same amount and at the same time as dividends paid to all Company common shareholders. PSUs The following table sets forth the activity related to vested and unvested PSUs: Number of Units Weighted-Average Grant-Date Fair Value Weighted-Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in millions) PSUs at December 31, 2019 (1) 723,533 $ 73.56 $ 61 Granted 299,936 $ 85.25 Conversions to common stock (243,100) $ 71.17 Forfeited (51,641) $ 75.81 PSUs at December 31, 2020 (1)(2)(3)(4) 728,728 $ 79.01 1.18 $ 66 (1) All PSUs outstanding at December 31, 2020 and December 31, 2019, are unvested PSUs. (2) Includes 225,182 PSUs granted in 2018 that are earned based on the Company’s achievement of earnings per share (“EPS”) during the three-year performance period which ends December 31, 2020, and are subject to the requisite service period which ended February 1, 2021. (3) Includes 211,799 PSUs granted in 2019 that are earned based on the Company’s achievement of EPS during the three-year performance period which ends December 31, 2021, and are subject to the requisite service period which ends February 1, 2022. (4) Includes 291,747 PSUs granted in 2020 that may be earned based on the Company’s achievement of EPS during the three-year performance period which ends December 31, 2022, and are subject to the requisite service period which ends February 1, 2023. Compensation cost associated with PSUs is determined based on the number of instruments granted, the fair value on the date of grant and the performance factor. The fair value is amortized on a straight-line basis, net of estimated forfeitures, over the requisite service period. Each PSU outstanding at December 31, 2020, is a restricted stock instrument that is subject to additional conditions and constitutes a contingent and unsecured promise by the Company to pay up to 1.5 shares per unit of the Company’s common stock on the conversion date for the PSU, contingent on the number of PSUs to be issued. PSUs have a performance period of three years and a vesting period of three years. The requisite service period of an award having both performance and service conditions is the longest of the explicit, implicit and derived service periods. The following table summarizes the total intrinsic value of the PSUs converted to common stock and the total grant-date fair value of PSUs vested (dollars in millions, except weighted-average grant-date fair value amounts): For the Years Ended December 31, 2020 2019 2018 Intrinsic value of PSUs converted to common stock $ 21 $ 33 $ 30 Grant-date fair value of PSUs vested $ 17 $ 21 $ 17 Weighted-average grant-date fair value of PSUs granted $ 85.25 $ 71.62 $ 77.75 As of December 31, 2020, there was $4 million of total unrecognized compensation cost related to non-vested PSUs. The cost is expected to be recognized over a weighted-average period of 1.4 years. PSUs provide for accelerated vesting if there is a change in control or upon certain terminations (as defined in the Omnibus Plan or the award certificate). PSUs include the right to receive dividend equivalents, which will accumulate and pay out in cash if and when the underlying shares are issued.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Employee Benefit Plans	Employee Benefit Plans The Company sponsors the Discover Financial Services Pension Plan (the “Discover Pension Plan”), which is a non-contributory defined benefit plan that is qualified under Section 401(a) of the Internal Revenue Code, for eligible employees in the United States. Effective December 31, 2008, the Discover Pension Plan was amended to discontinue the accrual of future benefits. The Company also sponsors the Discover Financial Services 401(k) Plan (the “Discover 401(k) Plan”), which is a defined contribution plan that is qualified under Section 401(a) of the Internal Revenue Code, for its eligible United States employees. Discover Pension Plan The Discover Pension Plan generally provides retirement benefits that are based on each participant’s years of credited service prior to 2009 and on compensation specified in the Discover Pension Plan. The Company’s policy is to fund at least the amounts sufficient to meet minimum funding requirements under the Employee Retirement Income Security Act of 1974, as amended. Net Periodic Benefit Cost (Income) Net periodic benefit cost expensed by the Company included the following components (dollars in millions): For the Years Ended December 31, 2020 2019 2018 Interest cost on projected benefit obligation $ 21 $ 23 $ 22 Expected return on plan assets (25) (29) (26) Net amortization 7 4 5 Net periodic benefit cost (income) $ 3 $ (2) $ 1 Accumulated Other Comprehensive Income Pretax amounts recognized in AOCI that have not yet been recognized as components of net periodic benefit cost consist of (dollars in millions): December 31, 2020 Net loss $ (299) Total $ (299) Benefit Obligations and Funded Status The following table provides a reconciliation of the changes in the benefit obligation and fair value of plan assets as well as a summary of the Discover Pension Plan’s funded status (dollars in millions): For the Years Ended December 31, 2020 2019 Reconciliation of benefit obligation Benefit obligation at beginning of year $ 650 $ 550 Interest cost 21 23 Actuarial losses 98 98 Benefits paid (21) (21) Benefit obligation at end of year 748 650 Reconciliation of fair value of plan assets Fair value of plan assets at beginning of year 525 455 Actual return on plan assets 110 91 Benefits paid (21) (21) Fair value of plan assets at end of year 614 525 Unfunded status (recorded in accrued expenses and other liabilities) $ (134) $ (125) Actuarial losses on the benefit obligation were primarily driven by changes in the discount rate for the years ended December 31, 2020 and 2019. Assumptions The following table presents the assumptions used to determine the benefit obligation: December 31, 2020 2019 Discount rate 2.47 % 3.30 % The following table presents the assumptions used to determine net periodic benefit cost: For the Years Ended December 31, 2020 2019 2018 Discount rate 3.30 % 4.27 % 3.68 % Expected long-term rate of return on plan assets 5.08 % 6.15 % 6.15 % The expected long-term rate of return on plan assets was estimated by computing a weighted-average return of the underlying long-term expected returns on the different asset classes, based on the target asset allocations. Asset class return assumptions are created by integrating information on past capital market performance, current levels of key economic indicators and the market insights of investment professionals. Individual asset classes are analyzed as part of a larger system, acknowledging both the interaction between asset classes and the influence of larger macroeconomic variables such as inflation and economic growth on the entire structure of capital markets. Medium and long-term economic outlooks for the United States and other major industrial economies are forecast in order to understand the range of possible economic scenarios and evaluate their likelihood. Historical relationships between key economic variables and asset class performance patterns are analyzed using empirical models. Finally, comprehensive asset class performance projections are created by blending descriptive asset class characteristics with capital market insight and the initial economic analyses. The expected long-term return on plan assets is a long-term assumption that generally is expected to remain the same from one year to the next but is adjusted if there is a material change in the target asset allocation and/or significant changes in fees and expenses paid by the Discover Pension Plan. Discover Pension Plan Assets The targeted asset allocation for 2021 by asset class is 72% and 28% for fixed income securities and equity securities, respectively. The Discover Financial Services Retirement Plan Investment Committee (the “Investment Committee”) determined the asset allocation targets for the Discover Pension Plan based on its assessment of business and financial conditions, demographic and actuarial data, funding characteristics and related risk factors. Other relevant factors, including industry practices and long-term historical and prospective capital market returns were considered as well. The Discover Pension Plan return objectives provide long-term measures for monitoring the investment performance against growth in the pension obligations. The overall allocation is expected to help protect the Discover Pension Plan’s funded status while generating sufficiently stable real returns (net of inflation) to help cover current and future benefit payments and to improve the Discover Pension Plan’s funded status. Total Discover Pension Plan portfolio performance is assessed by comparing actual returns with relevant benchmarks, such as the S&P 500 Index, the S&P 500 Total Return Index, the Russell 2000 Index and the MSCI All Country World Index. Both the fixed income and equity portions of the asset allocation use a combination of active and passive investment strategies and different investment styles. The fixed income asset allocation consists of longer duration fixed income securities in order to help reduce plan exposure to interest rate variation and to better correlate assets with obligations. The longer duration fixed income allocation is expected to help stabilize the funding status ratio over the long term. The asset mix of the Discover Pension Plan is reviewed by the Investment Committee on a regular basis. The asset allocation strategy will change over time in response to changes in the Discover Pension Plan’s funded status. Fair Value Measurements The Discover Pension Plan’s assets are stated at fair value. Quoted market prices in active markets are the best evidence of fair value and are used as the basis for the measurement, if available. If a quoted market price is not available, the estimate of the fair value is based on the best information available in the circumstances. The table below presents information about the Discover Pension Plan assets and indicates the level within the fair value hierarchy, as defined by ASC Topic 820, with which each item is associated as of the end of the current period. For a description of the fair value hierarchy, see Note 20: Fair Value Measurements (dollars in millions): Level 1 Level 2 Level 3 Net Asset Value Total Net Asset Allocation Balance at December 31, 2020 Assets Cash $ 15 $ — $ — $ — $ 15 3 % Domestic small/mid cap equity fund — 8 — — 8 1 % Emerging markets equity fund — — — 20 20 3 % Global equity fund — 83 4 49 136 22 % Domestic large cap equity fund — 10 — — 10 2 % Long duration credit fund — 243 — — 243 40 % Non-core fixed income fund — — 72 — 72 12 % United States Treasury securities 81 — — — 81 13 % Temporary investment fund — 31 — — 31 5 % Total assets 96 375 76 69 616 Liabilities Futures contracts — 2 — — 2 1 % Total liabilities — 2 — — 2 Net assets $ 96 $ 373 $ 76 $ 69 $ 614 100 % Balance at December 31, 2019 Assets Cash $ 7 $ — $ — $ — $ 7 1 % Domestic small/mid cap equity fund — 6 — — 6 1 % Emerging markets equity fund — — — 16 16 3 % Global equity fund — 73 3 45 121 23 % Domestic large cap equity fund — 8 — — 8 2 % Long duration credit fund — 205 — — 205 39 % Non-core fixed income fund — — 64 — 64 12 % United States Treasury securities 87 — — — 87 17 % Temporary investment fund — 15 — — 15 3 % Total assets 94 307 67 61 529 Liabilities Futures contracts — 4 — — 4 1 % Total liabilities — 4 — — 4 Net assets $ 94 $ 303 $ 67 $ 61 $ 525 100 % Cash Flows The Company does not expect to make any contributions to the Discover Pension Plan in 2021. Expected benefit payments associated with the Discover Pension Plan for each of the next five years and in aggregate for the years thereafter are as follows (dollars in millions): December 31, 2020 2021 $ 18 2022 $ 19 2023 $ 20 2024 $ 22 2025 $ 23 Following five years thereafter $ 140 Discover 401(k) Plan Under the Discover 401(k) Plan, eligible United States employees receive 401(k) matching contributions. Eligible employees also receive fixed employer contributions. The pretax expense associated with the Company contributions for the years ended December 31, 2020, 2019 and 2018 was $99 million, $87 million and $69 million, respectively.

Common and Preferred Stock

Common and Preferred Stock	12 Months Ended
	Dec. 31, 2020
Class of Stock Disclosures [Abstract]
Common and Preferred Stock	Common and Preferred Stock Preferred Stock Series C Preferred Stock At December 31, 2020, the Company had 5,700 shares of Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred Stock, Series C (“Series C preferred stock”), outstanding with a par value of $0.01 per share that were issued on October 31, 2017. Each share of Series C preferred stock has a liquidation preference of $100,000 and is represented by 100 depositary shares. Proceeds received from the Series C preferred stock issuance, net of underwriting discount, totaled approximately $563 million. The Series C preferred stock is redeemable at the Company’s option, subject to regulatory approval, either (i) in whole or in part on any dividend payment date on or after October 30, 2027 or (ii) in whole but not in part, at any time within 90 days following a regulatory capital event (as defined in the certificate of designations for the Series C preferred stock), in each case at a redemption price equal to $100,000 per share of Series C preferred stock plus declared and unpaid dividends. Any dividends declared on the Series C preferred stock will be payable semi-annually in arrears at a rate of 5.50% per annum through October 30, 2027. Thereafter, dividends declared on the Series C preferred stock will be payable quarterly in arrears at a floating rate equal to three-month LIBOR plus a spread of 3.076% per annum. Series D Preferred Stock On June 22, 2020, the Company issued and sold 5,000 shares of 6.125% Fixed-Rate Reset Non-Cumulative Perpetual Preferred Stock, Series D (“Series D preferred stock”), with a par value of $0.01 per share. Each share of Series D preferred stock has a liquidation preference of $1,000 and is represented by 100 depositary shares. Proceeds received from the Series D preferred stock issuance, net of underwriting discount and expenses, totaled approximately $493 million. The Series D preferred stock is redeemable at the Company’s option, subject to regulatory approval, either (i) in whole or in part during the three-month period prior to, and including, each reset date (as defined in the certificate of designations for the Series D preferred stock) or (ii) in whole but not in part, at any time within 90 days following a regulatory capital event (as defined in the certificate of designations for the Series D Preferred Stock), in each case at a redemption price equal to $1,000 per share of Series D preferred stock plus declared and unpaid dividends. Any dividends declared on the Series D preferred stock will be payable semi-annually in arrears at a rate of 6.125% per annum until September 23, 2025, after which the dividend rate will reset every five years to a fixed annual rate equal to the 5-year Treasury plus a spread of 5.783%. Common Stock Repurchase Program On July 18, 2019, the Company’s Board of Directors approved a share repurchase program authorizing the repurchase of up to $2.2 billion of its outstanding shares of common stock. The program expired on September 30, 2020. In January 2021, the Board of Directors approved a new share repurchase program authorizing up to $1.1 billion of share repurchases. The program expires on December 31, 2021. During the year ended December 31, 2020, the Company repurchased approximately 4 million shares for $320 million. The Company did not repurchase shares for the three months ended December 31, 2020.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income	12 Months Ended
	Dec. 31, 2020
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income	Accumulated Other Comprehensive Income Changes in each component of AOCI were as follows (dollars in millions): Unrealized Gains (Losses) on Available-for-Sale Investment Securities, Net of Tax (Losses) Gains on Cash Flow Hedges, Net of Tax Losses on Pension Plan, Net of Tax AOCI For the Year Ended December 31, 2020 Balance at December 31, 2019 $ 112 $ (17) $ (214) $ (119) Net change 172 5 (13) 164 Balance at December 31, 2020 $ 284 $ (12) $ (227) $ 45 For the Year Ended December 31, 2019 Balance at December 31, 2018 $ 10 $ 22 $ (188) $ (156) Net change 102 (39) (26) 37 Balance at December 31, 2019 $ 112 $ (17) $ (214) $ (119) For the Year Ended December 31, 2018 Balance at December 31, 2017 $ (5) $ 10 $ (157) $ (152) Cumulative effect of ASU No. 2018-02 adoption (1) (1) 3 (31) (29) Net change 16 9 — 25 Balance at December 31, 2018 $ 10 $ 22 $ (188) $ (156) (1) Represents the adjustment to AOCI as a result of adoption of ASU No. 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income, in the second quarter of 2018. The following table presents each component of OCI before reclassifications and amounts reclassified from AOCI for each component of OCI before- and after-tax (dollars in millions): Before Tax Tax (Expense) Benefit Net of Tax For the Year Ended December 31, 2020 Available-for-Sale Investment Securities Net unrealized holding gains arising during the period $ 227 $ (55) $ 172 Net change $ 227 $ (55) $ 172 Cash Flow Hedges Net unrealized losses arising during the period $ (7) $ 3 $ (4) Amounts reclassified from AOCI 12 (3) 9 Net change $ 5 $ — $ 5 Pension Plan Unrealized losses arising during the period $ (17) $ 4 $ (13) Net change $ (17) $ 4 $ (13) For the Year Ended December 31, 2019 Available-for-Sale Investment Securities Net unrealized holding gains arising during the period $ 135 $ (33) $ 102 Net change $ 135 $ (33) $ 102 Cash Flow Hedges Net unrealized losses arising during the period $ (42) $ 7 $ (35) Amounts reclassified from AOCI (5) 1 (4) Net change $ (47) $ 8 $ (39) Pension Plan Unrealized losses arising during the period $ (34) $ 8 $ (26) Net change $ (34) $ 8 $ (26) For the Year Ended December 31, 2018 Available-for-Sale Investment Securities Net unrealized holding gains arising during the period $ 23 $ (7) $ 16 Net change $ 23 $ (7) $ 16 Cash Flow Hedges Net unrealized gains arising during the period $ 17 $ (4) $ 13 Amounts reclassified from AOCI (6) 2 (4) Net change $ 11 $ (2) $ 9

Other Expense

Other Expense	12 Months Ended
	Dec. 31, 2020
Other Income and Expenses [Abstract]
Other Expense	Other Expense Total other expense includes the following components (dollars in millions): For the Years Ended December 31, 2020 2019 2018 Postage $ 93 $ 93 $ 86 Fraud losses and other charges 96 96 83 Supplies 51 34 29 Incentive expense 57 84 85 Impairment charges 59 — — Other expense 240 196 186 Total other expense $ 596 $ 503 $ 469

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income tax expense consisted of the following (dollars in millions): For the Years Ended December 31, 2020 2019 2018 Current United States federal $ 807 $ 836 $ 839 United States state and local 159 175 206 Total 966 1,011 1,045 Deferred United States federal (585) (116) (163) United States state and local (87) (17) (27) Total (672) (133) (190) Income tax expense $ 294 $ 878 $ 855 The following table reconciles the Company’s effective tax rate to the United States federal statutory income tax rate: For the Years Ended December 31, 2020 2019 2018 United States federal statutory income tax rate 21.0 % 21.0 % 21.0 % United States state, local and other income taxes, net of United States federal income tax benefits 3.4 3.5 3.6 Tax credits (4.4) (1.4) (1.3) Other 0.5 (0.2) 0.5 Effective income tax rate 20.5 % 22.9 % 23.8 % For the year ended December 31, 2020, income tax expense decreased $584 million, or 66.5%, and the effective income tax rate decreased 2.4 percentage points as compared to the year ended December 31, 2019. The decrease in income tax expense was primarily driven by a decrease in pretax income. The effective tax rate decreased primarily due to tax credits having a higher rate benefit on lower pretax income. Income tax expense increased $23 million, or 2.7%, and the effective tax rate decreased 0.9 percentage points for the year ended December 31, 2019, as compared to the year ended December 31, 2018. The increase in income tax expense was primarily driven by increased pretax income. The effective tax rate decreased primarily due to the resolution of certain tax matters. Deferred income taxes reflect the net tax effects of temporary differences between the financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when such differences are expected to reverse. Valuation allowances are provided to reduce deferred tax assets to an amount that is more likely than not to be realized. The Company evaluates the likelihood of realizing its deferred tax assets by estimating sources of future taxable income and the impact of tax planning strategies. Significant components of the Company’s net deferred income taxes, which are included in other assets in the Company’s consolidated statements of financial condition, were as follows (dollars in millions): December 31, 2020 2019 Deferred tax assets Allowance for credit losses $ 1,997 $ 819 Compensation and benefits 84 65 Other 73 50 Total deferred tax assets before valuation allowance 2,154 934 Valuation allowance (1) (1) Total deferred tax assets, net of valuation allowance 2,153 933 Deferred tax liabilities Depreciation and software amortization (172) (167) Unrealized gains (90) (33) Customer fees and rewards (37) (81) Deferred loan origination costs (21) (28) Debt exchange premium (17) (26) Intangibles (15) (28) Other (26) (19) Total deferred tax liabilities (378) (382) Net deferred tax assets $ 1,775 $ 551 A reconciliation of beginning and ending unrecognized tax benefits is as follows (dollars in millions): For the Years Ended December 31, 2020 2019 2018 Balance at beginning of period $ 61 $ 83 $ 123 Additions Current year tax positions 5 4 5 Prior year tax positions 3 — 6 Reductions Prior year tax positions — (22) (17) Settlements with taxing authorities (2) — (25) Expired statute of limitations (11) (4) (9) Balance at end of period (1) $ 56 $ 61 $ 83 (1) For the years ended December 31, 2020, 2019 and 2018, amounts included $51 million, $54 million and $74 million, respectively, of unrecognized tax benefits, which, if recognized, would favorably affect the effective tax rate. The Company recognizes accrued interest and penalties related to unrecognized tax benefits as a component of income tax expense. Interest and penalties related to unrecognized tax benefits were $12 million and $14 million for the years ended December 31, 2020 and 2019, respectively. The Company is subject to examination by the Internal Revenue Service (“IRS”) and tax authorities in various state, local and foreign tax jurisdictions. Currently the IRS Office of Appeals is reviewing years 2011 – 2015 and the IRS is examining 2018. The Company regularly assesses the likelihood of additional assessments or settlements in each of the taxing jurisdictions resulting from these and subsequent years' examinations. It is reasonably possible that settlements of the IRS appeal of the years 2011 – 2015 and certain state audits may be made within 12 months of the reporting date. At this time, the Company believes it is reasonably possible that a reduction of unrecognized tax benefits of $24 million could be recognized. The Company believes that its reserves are sufficient to cover any tax, penalties and interest that would result from such examinations.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share The following table presents the calculation of basic and diluted earnings per share (dollars in millions, except per share amounts): For the Years Ended December 31, 2020 2019 2018 Numerator Net income $ 1,141 $ 2,957 $ 2,742 Preferred stock dividends (31) (31) (31) Net income available to common stockholders 1,110 2,926 2,711 Income allocated to participating securities (6) (18) (22) Net income allocated to common stockholders $ 1,104 $ 2,908 $ 2,689 Denominator Weighted-average shares of common stock outstanding 307 320 344 Effect of dilutive common stock equivalents — — 1 Weighted-average shares of common stock outstanding and common stock equivalents 307 320 345 Basic earnings per common share $ 3.60 $ 9.09 $ 7.81 Diluted earnings per common share $ 3.60 $ 9.08 $ 7.79 Anti-dilutive securities were not material and had no impact on the computation of diluted EPS for the years ended December 31, 2020, 2019 and 2018.

Capital Adequacy

Capital Adequacy	12 Months Ended
	Dec. 31, 2020
Broker-Dealer, Net Capital Requirement, SEC Regulation [Abstract]
Capital Adequacy	Capital Adequacy The Company is subject to the capital adequacy guidelines of the Federal Reserve and Discover Bank, the Company’s banking subsidiary, is subject to various regulatory capital requirements as administered by the FDIC. Failure to meet minimum capital requirements can result in the initiation of certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the financial position and operating results of the Company and Discover Bank. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, the Company and Discover Bank must meet specific capital guidelines that involve quantitative measures of assets, liabilities and certain off-balance sheet items, as calculated under regulatory guidelines. Capital amounts and classification are also subject to qualitative judgments by the regulators about components, risk weightings and other factors. The Company and Discover Bank are subject to regulatory and capital rules issued by the Federal Reserve and FDIC, respectively, under the Basel Committee’s December 2010 framework (“Basel III rules”). The Basel III rules, which became effective for the Company in January 2015, were subject to phase-in periods through the end of 2018, based on the Company being classified as a “Standardized Approach” entity. As of January 1, 2019, the Basel III rules subject to transition have all been fully phased in with the exception of certain transition provisions that were frozen pursuant to regulation issued in November 2017. Pursuant to a final rule issued in July 2019, the transition provisions that were previously frozen have been replaced with new permanent rules which became effective in April 2020. Additionally, on March 27, 2020, federal bank regulatory agencies announced an interim final rule, which has since been adopted as a final rule, that allows banks that have implemented CECL the option to delay for two years the estimated impact of CECL on regulatory capital, followed by a three-year transition period. For purposes of calculating regulatory capital, the Company has elected to defer recognition of the estimated impact of CECL on regulatory capital for two years in accordance with the federal bank regulatory agencies’ final rule published on September 30, 2020. Pursuant to the final rule, the estimated impact of CECL on regulatory capital will be phased in over a three-year period beginning in 2022. As of December 31, 2020, the Company and Discover Bank met all Basel III minimum capital ratio requirements to which they were subject. The Company and Discover Bank also met the requirements to be considered “well-capitalized” under Regulation Y and prompt corrective action regulations, respectively, and there have been no conditions or events that management believes have changed the Company’s or Discover Bank’s category. To be categorized as “well-capitalized,” the Company and Discover Bank must maintain minimum capital ratios as set forth in the table below. The following table shows the actual capital amounts and ratios of the Company and Discover Bank and comparisons of each to the regulatory minimum and “well-capitalized” requirements (dollars in millions): Actual Minimum Capital Capital Requirements Amount Ratio (1) Amount Ratio Amount (2) Ratio (2) December 31, 2020 Total capital (to risk-weighted assets) Discover Financial Services $ 14,711 16.1 % $ 7,298 ≥8.0% $ 9,123 ≥10.0% Discover Bank $ 14,507 16.1 % $ 7,214 ≥8.0% $ 9,018 ≥10.0% Tier 1 capital (to risk-weighted assets) Discover Financial Services $ 13,006 14.3 % $ 5,474 ≥6.0% $ 5,474 ≥6.0% Discover Bank $ 12,415 13.8 % $ 5,411 ≥6.0% $ 7,214 ≥8.0% Tier 1 capital (to average assets) Discover Financial Services $ 13,006 10.9 % $ 4,757 ≥4.0% N/A N/A Discover Bank $ 12,415 10.5 % $ 4,709 ≥4.0% $ 5,886 ≥5.0% Common Equity Tier 1 (to risk-weighted assets) Discover Financial Services $ 11,950 13.1 % $ 4,105 ≥4.5% N/A N/A Discover Bank $ 12,415 13.8 % $ 4,058 ≥4.5% $ 5,862 ≥6.5% December 31, 2019 Total capital (to risk-weighted assets) Discover Financial Services $ 13,250 13.5 % $ 7,860 ≥8.0% $ 9,825 ≥10.0% Discover Bank $ 13,441 13.8 % $ 7,776 ≥8.0% $ 9,720 ≥10.0% Tier 1 capital (to risk-weighted assets) Discover Financial Services $ 11,595 11.8 % $ 5,895 ≥6.0% $ 5,895 ≥6.0% Discover Bank $ 11,203 11.5 % $ 5,832 ≥6.0% $ 7,776 ≥8.0% Tier 1 capital (to average assets) Discover Financial Services $ 11,595 10.3 % $ 4,482 ≥4.0% N/A N/A Discover Bank $ 11,203 10.1 % $ 4,435 ≥4.0% $ 5,544 ≥5.0% Common Equity Tier 1 (to risk-weighted assets) Discover Financial Services $ 11,032 11.2 % $ 4,421 ≥4.5% N/A N/A Discover Bank $ 11,203 11.5 % $ 4,374 ≥4.5% $ 6,318 ≥6.5% (1) Capital ratios are calculated based on the Basel III Standardized Approach rules, subject to applicable transition provisions, including CECL transition provisions. (2) The Basel III rules do not establish well-capitalized thresholds for these measures for bank holding companies. Existing well-capitalized thresholds established in the Federal Reserve’s Regulation Y have been included where available.

Commitments, Contingencies and

Commitments, Contingencies and Guarantees	12 Months Ended
	Dec. 31, 2020
Commitments Contingencies and Guarantees [Abstract]
Commitments, Contingencies and Guarantees	Commitments, Contingencies and Guarantees In the normal course of business, the Company enters into a number of off-balance sheet commitments, transactions and obligations under guarantee arrangements that expose the Company to varying degrees of risk. The Company’s commitments, contingencies and guarantee relationships are described below. Commitments Unused Credit Arrangements At December 31, 2020, the Company had unused credit arrangements for loans of approximately $213.7 billion. Such arrangements arise primarily from agreements with customers for unused lines of credit on certain credit cards and certain other loan products, provided there is no violation of conditions in the related agreements. These arrangements, substantially all of which the Company can terminate at any time and which do not necessarily represent future cash requirements, are periodically reviewed based on account usage, customer creditworthiness and loan qualification. As the Company’s credit card loans are unconditionally cancellable, no liability for expected credit losses is required for unused lines of credit. For all other loans, the Company records a liability for expected credit losses for unfunded commitments, which is presented as part of accrued expenses and other liabilities in the consolidated statements of financial condition. Contingencies See Note 19: Litigation and Regulatory Matters for a description of potential liability arising from pending litigation or regulatory proceedings involving the Company. Guarantees The Company has obligations under certain guarantee arrangements, including contracts, indemnification agreements and representations and warranties, which contingently require the Company to make payments to the guaranteed party based on changes in an underlying asset, liability or equity security of a guaranteed party, rate or index. Also included as guarantees are contracts that contingently require the Company to make payments to a guaranteed party based on another entity’s failure to perform under an agreement. The Company’s use of guarantees is disclosed below by type of guarantee. Securitizations Representations and Warranties As part of the Company’s financing activities, the Company provides representations and warranties that certain assets pledged as collateral in secured borrowing arrangements conform to specified guidelines. Due diligence is performed by the Company, which is intended to ensure that asset guideline qualifications are met. If the assets pledged as collateral do not meet certain conforming guidelines, the Company may be required to replace, repurchase or sell such assets. In its credit card securitization activities, the Company would replace nonconforming receivables through the allocation of excess seller’s interest or from additional transfers from the unrestricted pool of receivables. If the Company could not add enough receivables to satisfy the requirement, an early amortization (or repayment) of investors’ interests would be triggered. In its student loan securitizations, the Company would generally repurchase the loans from the trust at the outstanding principal amount plus interest. The maximum potential amount of future payments the Company could be required to make would be equal to the current outstanding balances of third-party investor interests in credit card asset-backed securities and the principal amount of any student loan secured borrowings, plus any unpaid interest for the corresponding secured borrowings. The Company has recorded substantially all of the maximum potential amount of future payments in long-term borrowings on the Company’s consolidated statements of financial condition. The Company has not recorded any incremental contingent liability associated with its secured borrowing representations and warranties. Management believes that the probability of having to replace, repurchase or sell assets pledged as collateral under secured borrowing arrangements, including an early amortization event, is low. Counterparty Settlement Guarantees Diners Club and DFS Services LLC (on behalf of PULSE) have various counterparty exposures, which are listed below: • Merchant Guarantee . Diners Club has entered into contractual relationships with certain international merchants, which generally include travel-related businesses, for the benefit of all Diners Club licensees. The licensees hold the primary liability to settle the transactions of their customers with these merchants. However, Diners Club retains a counterparty exposure if a licensee fails to meet its financial payment obligation to one of these merchants. • ATM Guarantee. PULSE entered into contractual relationships with certain international ATM acquirers in which DFS Services LLC retains counterparty exposure if an issuer fails to fulfill its settlement obligation. • Global Network Alliance Guarantee. Discover Network, Diners Club and PULSE have entered into contractual relationships with certain international payment networks in which DFS Services LLC retains the counterparty exposure if a network fails to fulfill its settlement obligation. The maximum potential amount of future payments related to such contingent obligations is dependent upon the transaction volume processed between the time a potential counterparty defaults on its settlement and the time at which the Company disables the settlement of any further transactions for the defaulting party. The Company has some contractual remedies to offset these counterparty settlement exposures (such as letters of credit or pledged deposits), however, there is no limitation on the maximum amount the Company may be liable to pay. The actual amount of the potential exposure cannot be quantified as the Company cannot determine whether particular counterparties will fail to meet their settlement obligations. In the event that all licensees and/or issuers were to become unable to settle their transactions, the Company estimates its maximum potential counterparty exposures to these settlement guarantees would be approximately $60 million as of December 31, 2020. The Company believes that the estimated amounts of maximum potential future payments are not representative of the Company’s actual potential loss exposure given Diners Club’s and PULSE’s insignificant historical losses from these counterparty exposures. As of December 31, 2020, the Company had not recorded any contingent liability in the consolidated financial statements for these counterparty exposures and management believes that the probability of any payments under these arrangements is low. Discover Network Merchant Chargeback Guarantees The Company operates the Discover Network, issues payment cards and permits third parties to issue payment cards. The Company is contingently liable for certain transactions processed on the Discover Network in the event of a dispute between the payment card customer and a merchant. The contingent liability arises if the disputed transaction involves a merchant or merchant acquirer with whom the Discover Network has a direct relationship. If a dispute is resolved in the customer’s favor, the Discover Network will credit or refund the disputed amount to the Discover Network card issuer, who in turn credits its customer’s account. The Discover Network will then charge back the disputed amount of the payment card transaction to the merchant or merchant acquirer, where permitted by the applicable agreement, to seek recovery of amounts already paid to the merchant for payment card transactions. If the Discover Network is unable to collect the amount subject to dispute from the merchant or merchant acquirer (e.g., in the event of merchant default or dissolution or after expiration of the time period for chargebacks in the applicable agreement), the Discover Network will bear the loss for the amount credited or refunded to the customer. In most instances, a loss by the Discover Network is unlikely to arise in connection with payments on card transactions because most products or services are delivered when purchased and credits are issued by merchants on returned items in a timely fashion, thus minimizing the likelihood of cardholder disputes with respect to amounts paid by the Discover Network. However, where the product or service is not scheduled to be provided to the customer until a later date following the purchase, the likelihood of a contingent payment obligation by the Discover Network increases. Losses related to merchant chargebacks were not material for the years ended December 31, 2020, 2019 and 2018. The maximum potential amount of obligations of the Discover Network arising as a result of such contingent obligations is estimated to be the portion of the total Discover Network transaction volume processed to date for which timely and valid disputes may be raised under applicable law and relevant issuer and customer agreements. There is no limitation on the maximum amount the Company may be liable to pay to issuers. However, the Company believes that such amount is not representative of the Company’s actual potential loss exposure based on the Company’s historical experience. The actual amount of the potential exposure cannot be quantified as the Company cannot determine whether the current or cumulative transaction volumes may include or result in disputed transactions. The following table summarizes certain information regarding merchant chargeback guarantees (dollars in millions): For the Years Ended December 31, 2020 2019 2018 Aggregate sales transaction volume (1) $ 175,026 $ 172,463 $ 158,910 (1) Represents transactions processed on the Discover Network for which a potential liability exists that, in aggregate, can differ from credit card sales volume. The Company did not record any contingent liability in the consolidated financial statements for merchant chargeback guarantees as of December 31, 2020 or 2019. The Company mitigates the risk of potential loss exposure by withholding settlement from merchants, obtaining third-party guarantees, or obtaining escrow deposits or letters of credit from certain merchant acquirers or merchants that are considered higher risk due to various factors such as time delays in the delivery of products or services. As of December 31, 2020 and 2019, the Company had escrow deposits and settlement withholdings of $16 million and $8 million, respectively, which are recorded in interest-bearing deposit accounts and accrued expenses and other liabilities on the Company’s consolidated statements of financial condition.

Litigation and Regulatory Matte

Litigation and Regulatory Matters	12 Months Ended
	Dec. 31, 2020
Loss Contingency [Abstract]
Litigation and Regulatory Matters	Litigation and Regulatory Matters In the normal course of business, from time to time, the Company has been named as a defendant in various legal actions, including arbitrations, class actions and other litigation, arising in connection with its activities. Certain of the actual or threatened legal actions include claims for substantial compensatory and/or punitive damages or claims for indeterminate amounts of damages. The litigation process is not predictable and can lead to unexpected results. The Company contests liability and/or the amount of damages as appropriate in each pending matter. The Company has historically offered its customers an arbitration clause in its customer agreements. The arbitration clause allows the Company and its customers to quickly and economically resolve disputes. Additionally, the arbitration clause has in some instances limited the costs of, and the Company’s exposure to, litigation. Future legal and regulatory challenges and prohibitions may cause the Company to discontinue its offering and use of such clauses. From time to time, the Company is involved in legal actions challenging its arbitration clause. Bills may be periodically introduced in Congress to directly or indirectly prohibit the use of pre-dispute arbitration clauses. The Company is also involved, from time to time, in other reviews, investigations and proceedings (both formal and informal) by governmental agencies regarding the Company’s business including, among other matters, consumer regulatory, accounting, tax and other operational matters, some of which may result in significant adverse judgments, settlements, fines, penalties, injunctions, decreases in regulatory ratings, customer restitution or other relief, which could materially impact the Company’s consolidated financial statements, increase its cost of operations, or limit its ability to execute its business strategies and engage in certain business activities. Certain subsidiaries of the Company are subject to a consent order with the Consumer Financial Protection Bureau (the “CFPB”) regarding certain student loan servicing practices, as described below. Pursuant to powers granted under federal banking laws, regulatory agencies have broad and sweeping discretion and may assess civil money penalties, require changes to certain business practices or require customer restitution at any time. In accordance with applicable accounting guidance, the Company establishes an accrued liability for legal and regulatory matters when those matters present loss contingencies that are both probable and estimable. Litigation and regulatory settlement related expense was $31 million for the year ended December 31, 2020, and not material for the years ended December 31, 2019 and 2018. There may be an exposure to loss in excess of any amounts accrued. The Company believes the estimate of the aggregate range of reasonably possible losses (meaning those losses the likelihood of which is more than remote but less than likely) in excess of the amounts that the Company has accrued for legal and regulatory proceedings is up to $220 million. This estimated range of reasonably possible losses is based upon currently available information for those proceedings in which the Company is involved and takes into account the Company’s best estimate of such losses for those matters for which an estimate can be made. It does not represent the Company’s maximum potential loss exposure. Various aspects of the legal proceedings underlying the estimated range will change from time to time and actual results may vary significantly from the estimate. The Company’s estimated range noted above involves significant judgment, given the varying stages of the proceedings, the existence of numerous yet to be resolved issues, the breadth of the claims (often spanning multiple years and, in some cases, a wide range of business activities), unspecified damages and/or the novelty of the legal issues presented. The outcome of pending matters could adversely affect the Company’s reputation and be material to the Company’s consolidated financial condition, operating results and cash flows for a particular future period, depending on, among other things, the level of the Company’s income for such period. On July 22, 2015, the Company announced that its subsidiaries, Discover Bank, SLC and Discover Products Inc. (the “Discover Subsidiaries”), agreed to a consent order with the CFPB with respect to certain student loan servicing practices (the “2015 Order”). The 2015 Order expired in July 2020. On December 22, 2020, the Discover Subsidiaries agreed to a consent order (the “2020 Order”) with the CFPB resolving the agency’s investigation into Discover Bank’s compliance with the 2015 Order. In connection with the 2020 order, Discover is required to implement a redress and compliance plan and must pay at least $10 million in consumer redress to consumers who may have been harmed and paid $25 million civil money penalty to the CFPB. On March 8, 2016, a class action lawsuit was filed against the Company, other credit card networks, other issuing banks and EMVCo in the United States District Court for the Northern District of California (B&R Supermarket, Inc., d/b/a Milam’s Market, et al. v. Visa, Inc. et al.) alleging a conspiracy by the defendants to shift fraud liability to merchants with the migration to the EMV security standard and chip technology. The plaintiffs assert joint and several liability among the defendants and seek unspecified damages, including treble damages, attorneys’ fees, costs and injunctive relief. In May 2017, the Court entered an order transferring the entire action to a federal court in New York that is presiding over certain related claims that are pending in the actions consolidated as MDL 1720. On August 28, 2020, the Court granted the plaintiffs’ Motion to Certify a Class. The defendants appealed the ruling on September 11, 2020. The Company filed a Motion to Compel Arbitration on October 30, 2020. The Company is not in a position at this time to assess the likely outcome or its exposure, if any, with respect to this matter, but will seek to vigorously defend against all claims asserted by the plaintiffs.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. ASC Topic 820, Fair Value Measurement , provides a three-level hierarchy for classifying financial instruments, which is based on whether the inputs to the valuation techniques used to measure the fair value of each financial instrument are observable or unobservable. It also requires certain disclosures about those measurements. The three-level valuation hierarchy is as follows: • Level 1 : Fair values determined by Level 1 inputs are defined as those that utilize quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company has the ability to access. • Level 2 : Fair values determined by Level 2 inputs are those that utilize inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices for similar assets and liabilities in active or inactive markets, quoted prices for the identical assets in an inactive market and inputs other than quoted prices that are observable for the asset or liability, such as interest rates and yield curves that are observable at commonly quoted intervals. The Company evaluates factors such as the frequency of transactions, the size of the bid-ask spread and the significance of adjustments made when considering transactions involving similar assets or liabilities to assess the relevance of those observed prices. If relevant and observable prices are available, the fair values of the related assets or liabilities would be classified as Level 2. • Level 3 : Fair values determined by Level 3 inputs are those based on unobservable inputs and include situations where there is little, if any, market activity for the asset or liability being valued. In instances in which the inputs used to measure fair value may fall into different levels of the fair value hierarchy, the level in the fair value hierarchy within which the fair value measurement in its entirety is classified is based on the lowest level input that is significant to the fair value measurement in its entirety. The Company may utilize both observable and unobservable inputs in determining the fair values of financial instruments classified within the Level 3 category. The determination of classification of its financial instruments within the fair value hierarchy is performed at least quarterly by the Company. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires judgment and involves consideration of factors specific to the asset or liability. Furthermore, certain techniques used to measure fair value involve some degree of judgment and, as a result, are not necessarily indicative of the amounts the Company would realize in a current market exchange. Assets and Liabilities Measured at Fair Value on a Recurring Basis Assets and liabilities measured at fair value on a recurring basis are as follows (dollars in millions): Quoted Price in Active Markets Significant Other Observable Inputs Significant Unobservable Inputs Total Balance at December 31, 2020 Assets Fair value - OCI United States Treasury securities $ 9,354 $ — $ — $ 9,354 Residential mortgage-backed securities - Agency — 300 — 300 Available-for-sale investment securities $ 9,354 $ 300 $ — $ 9,654 Fair value - Net income Derivative financial instruments - fair value hedges (1) $ — $ 1 $ — $ 1 Balance at December 31, 2019 Assets Fair value - OCI United States Treasury securities $ 9,906 $ — $ — $ 9,906 Residential mortgage-backed securities - Agency — 417 — 417 Available-for-sale investment securities $ 9,906 $ 417 $ — $ 10,323 Liabilities Fair value - OCI Derivative financial instruments - cash flow hedges (1) $ — $ 2 $ — $ 2 Fair value - Net income Derivative financial instruments - fair value hedges (1) $ — $ 4 $ — $ 4 Derivative financial instruments - foreign exchange forward contracts (1) $ — $ 1 $ — $ 1 (1) Derivative instrument carrying values in an asset or liability position are presented as part of other assets or accrued expenses and other liabilities, respectively, in the Company’s consolidated statements of financial condition. Available-for-Sale Investment Securities Investment securities classified as available-for-sale consist of United States Treasury securities and residential mortgage-backed securities. The fair value estimates of investment securities classified as Level 1, consisting of United States Treasury securities, are determined based on quoted market prices for the same securities. The Company classifies residential mortgage-backed securities as Level 2, the fair value estimates of which are based on the best information available. This data may consist of observed market prices, broker quotes or discounted cash flow models that incorporate assumptions such as benchmark yields, issuer spreads, prepayment speeds, credit ratings and losses, the priority of which may vary based on availability of information. The Company validates the fair value estimates provided by pricing services primarily by comparison to valuations obtained through other pricing sources. The Company evaluates pricing variances among different pricing sources to ensure that the valuations utilized are reasonable. The Company also corroborates the reasonableness of the fair value estimates with analysis of trends of significant inputs, such as market interest rate curves. The Company further performs due diligence in understanding the procedures and techniques performed by the pricing services to derive fair value estimates. At December 31, 2020, amounts reported in residential mortgage-backed securities reflect government-rated obligations issued by Fannie Mae, Freddie Mac and Ginnie Mae with an aggregate par value of $286 million, a weighted-average coupon of 2.77% and a weighted-average remaining maturity of three years. Derivative Financial Instruments The Company’s derivative financial instruments consist of interest rate swaps and foreign exchange forward contracts. These instruments are classified as Level 2 as their fair values are estimated using proprietary pricing models, containing certain assumptions based on readily observable market-based inputs, including interest rate curves, option volatility and foreign currency forward and spot rates. In determining fair values, the pricing models use widely accepted valuation techniques including discounted cash flow analysis on the expected cash flows of each derivative. This analysis reflects the contractual terms of the derivatives, including the period to maturity and the observable market-based inputs. The fair values of the interest rate swaps are determined using the market standard methodology of netting the discounted future fixed cash receipts (or payments) and the discounted expected variable cash payments (or receipts). The variable cash payments are based on an expectation of future interest rates derived from the observable market interest rate curves. The Company considers collateral and master netting agreements that mitigate credit exposure to counterparties in determining the counterparty credit risk valuation adjustment. The fair values of the currency instruments are valued comparing the contracted forward exchange rate pertaining to the specific contract maturities to the current market exchange rate. The Company validates the fair value estimates of interest rate swaps primarily through comparison to the fair value estimates computed by the counterparties to each of the derivative transactions. The Company evaluates pricing variances among different pricing sources to ensure that the valuations utilized are reasonable. The Company also corroborates the reasonableness of the fair value estimates with analysis of trends of significant inputs, such as market interest rate curves. The Company performs due diligence in understanding the impact to any changes to the valuation techniques performed by proprietary pricing models prior to implementation, working closely with the third-party valuation service, and reviews the control objectives of the service at least annually. The Company corroborates the fair value of foreign exchange forward contracts through independent calculation of the fair value estimates. As of October 16, 2020, the Company revised its valuation methodology to reflect changes made by central clearinghouses that changed the discounting methodology and interest calculation of cash variation margin from OIS to the Secured Overnight Financing Rate (“SOFR”) for USD cleared interest rate swaps. Accordingly, the adjustments to the Company’s valuation methodology will result in valuations for cleared interest rate swaps that better reflect prices obtainable in the markets in which the Company transacts. Pursuant to ASC Topic 848, the Company has elected and applied certain optional expedients and exceptions that provide contract modification and hedge accounting relief to eligible interest rate swaps affected by the change in the discounting methodology. The changes in valuation methodology are applied prospectively as a change in accounting estimate and are immaterial to the Company’s financial statements. Assets and Liabilities Measured at Fair Value on a Non-Recurring Basis The Company also has assets that under certain conditions are subject to measurement at fair value on a non-recurring basis. These assets include those associated with acquired businesses, including goodwill and other intangible assets. For these assets, measurement at fair value in periods subsequent to the initial recognition of the assets is applicable if one or more of the assets is determined to be impaired. The Company recognized $59 million of impairments to intangible assets for the year ended December 31, 2020. See Note 7: Goodwill and Intangible Assets for more information on the impact of COVID-19 on intangible assets. The Company had no material impairments related to these assets during the year ended December 31, 2019. Financial Instruments Measured at Other Than Fair Value The following tables disclose the estimated fair value of the Company’s financial assets and financial liabilities that are not required to be carried at fair value (dollars in millions): Balance at December 31, 2020 Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Carrying Value Assets Amortized cost Residential mortgage-backed securities - Agency $ — $ 269 $ — $ 269 $ 260 Held-to-maturity investment securities $ — $ 269 $ — $ 269 $ 260 Net loan receivables $ — $ — $ 91,200 $ 91,200 $ 82,223 Carrying value approximates fair value (1) Cash and cash equivalents $ 13,564 $ — $ — $ 13,564 $ 13,564 Restricted cash $ 25 $ — $ — $ 25 $ 25 Other short-term investments $ 2,200 $ — $ — $ 2,200 $ 2,200 Accrued interest receivables (2) $ — $ 992 $ — $ 992 $ 992 Liabilities Amortized cost Time deposits (3) $ — $ 29,090 $ — $ 29,090 $ 28,269 Long-term borrowings - owed to securitization investors $ — $ 10,794 $ 130 $ 10,924 $ 10,840 Other long-term borrowings — 11,418 — 11,418 10,401 Long-term borrowings $ — $ 22,212 $ 130 $ 22,342 $ 21,241 Carrying value approximates fair value (1) Accrued interest payables (2) $ — $ 233 $ — $ 233 $ 233 (1) The carrying values of these assets and liabilities approximate fair value due to their short-term nature. (2) Accrued interest receivable and payable carrying values are presented as part of other assets or accrued expenses and other liabilities, respectively, in the Company’s consolidated statements of financial condition. (3) Excludes deposits without contractually defined maturities for all periods presented. Balance at December 31, 2019 Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Carrying Value Assets Amortized cost Residential mortgage-backed securities - Agency $ — $ 274 $ — $ 274 $ 272 Held-to-maturity investment securities $ — $ 274 $ — $ 274 $ 272 Net loan receivables $ — $ — $ 96,094 $ 96,094 $ 92,511 Carrying value approximates fair value (1) Cash and cash equivalents $ 6,924 $ — $ — $ 6,924 $ 6,924 Restricted cash $ 40 $ — $ — $ 40 $ 40 Accrued interest receivables (2) $ — $ 1,044 $ — $ 1,044 $ 1,044 Liabilities Amortized cost Time deposits (3) $ — $ 34,910 $ — $ 34,910 $ 34,381 Long-term borrowings - owed to securitization investors $ — $ 14,211 $ 172 $ 14,383 $ 14,284 Other long-term borrowings — 12,189 — 12,189 11,417 Long-term borrowings $ — $ 26,400 $ 172 $ 26,572 $ 25,701 Carrying value approximates fair value (1) Accrued interest payables (2) $ — $ 283 $ — $ 283 $ 283 (1) The carrying values of these assets and liabilities approximate fair value due to their short-term nature. (2) Accrued interest receivable and payable carrying values are presented as part of other assets or accrued expenses and other liabilities, respectively, in the Company’s consolidated statements of financial condition. (3) Excludes deposits without contractually defined maturities for all periods presented.

Derivatives and Hedging Activit

Derivatives and Hedging Activities	12 Months Ended
	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives and Hedging Activities	Derivatives and Hedging Activities The Company uses derivatives to manage its exposure to various financial risks. The Company does not enter into derivatives for trading or speculative purposes. Certain derivatives used to manage the Company’s exposure to foreign currency are not designated as hedges and do not qualify for hedge accounting. Derivatives may give rise to counterparty credit risk, which generally is addressed through collateral arrangements as described under the sub-heading “— Collateral Requirements and Credit-Risk Related Contingency Features.” The Company enters into derivative transactions with established dealers that meet minimum credit criteria established by the Company. All counterparties must be pre-approved prior to engaging in any transaction with the Company. Counterparties are monitored on a regular basis by the Company to ensure compliance with the Company’s risk policies and limits. In determining the counterparty credit risk valuation adjustment for the fair values of derivatives, the Company considers collateral and legally enforceable master netting agreements that mitigate credit exposure to related counterparties. All derivatives are recorded in other assets at their gross positive fair values and in accrued expenses and other liabilities at their gross negative fair values. See Note 20: Fair Value Measurements for a description of the valuation methodologies used for derivatives. Cash collateral amounts associated with derivative positions that are cleared through an exchange are legally characterized as settlement of the derivative positions. Such collateral amounts are reflected as offsets to the associated derivatives balances recorded in other assets or in accrued expenses and other liabilities. Other cash collateral posted and held balances are recorded in other assets and deposits, respectively, in the consolidated statements of financial condition. Collateral amounts recorded in the consolidated statements of financial condition are based on the net collateral posted or held position for each applicable legal entity’s master netting arrangement with each counterparty. Derivatives Designated as Hedges Derivatives designated and qualifying as a hedge of the exposure to variability in expected future cash flows arising from changes in interest rates, or other types of forecasted transactions, are considered cash flow hedges. Derivatives designated and qualifying as a hedge of the exposure to changes in the fair value of an asset, liability, or firm commitment attributable to a particular risk, such as interest rate risk, are considered fair value hedges. Cash Flow Hedges The Company uses interest rate swaps to manage its exposure to changes in interest rates related to future cash flows resulting from interest receipts from credit card receivables and interest payments on credit card securitized debt and deposits. The Company’s outstanding cash flow hedges are for an initial maximum period of two years for credit card receivables. The derivatives are designated as hedges of the risk of changes in cash flows on the Company’s Prime rate-based interest receipts and Federal Funds rate-based interest payments and qualify for hedge accounting in accordance with ASC Topic 815, Derivatives and Hedging (“ASC 815”). The change in the fair value of derivatives designated as cash flow hedges is recorded in OCI and is subsequently reclassified into earnings in the period that the hedged forecasted cash flows affect earnings. Amounts reported in AOCI related to derivatives at December 31, 2020, will be reclassified to interest income and interest expense as interest receipts and payments are accrued on the Company’s then outstanding credit card receivables and certain floating-rate securitized debt, respectively. During the next 12 months, the Company estimates it will reclassify $3 million of pretax income and expense to earnings related to its derivatives designated as cash flow hedges. Fair Value Hedges The Company is exposed to changes in fair value of its fixed-rate debt obligations due to changes in interest rates. The Company uses interest rate swaps to manage its exposure to changes in fair value of certain fixed-rate long-term borrowings, including securitized debt and bank notes, attributable to changes in LIBOR or OIS rate, benchmark interest rates as defined by ASC 815. These interest rate swaps qualify as fair value hedges in accordance with ASC 815. Changes in both (i) the fair values of the derivatives and (ii) the hedged long-term borrowings relating to the risk being hedged are recorded in interest expense. The changes generally provide substantial offset to one another. Derivatives Not Designated as Hedges Foreign Exchange Forward Contracts The Company has foreign exchange forward contracts that are economic hedges and are not designated as accounting hedges. The Company enters into foreign exchange forward contracts to manage foreign currency risk. Changes in the fair value of these contracts are recorded in other income. Derivatives Cleared Through an Exchange Cash variation margin payments on derivatives cleared through an exchange are legally considered settlement payments and are accounted for with corresponding derivative positions as one unit of account and not presented separately as collateral. With settlement payments on derivative positions cleared through this exchange reflected as offsets to the associated derivative asset and liability balances, the fair values of derivative instruments and collateral balances shown are generally reduced. Derivatives Activity The following table summarizes the fair value (including accrued interest) and outstanding notional amounts of derivative instruments and related collateral balances (dollars in millions): December 31, 2020 December 31, 2019 Notional Number of Derivative Assets Derivative Liabilities Notional Derivative Assets Derivative Liabilities Derivatives designated as hedges Interest rate swaps—cash flow hedge $ 250 1 $ — $ — $ 900 $ — $ 2 Interest rate swaps—fair value hedge $ 11,625 15 1 — $ 14,275 — 4 Derivatives not designated as hedges Foreign exchange forward contracts (1) $ 24 6 — — $ 38 — 1 Total gross derivative assets/liabilities (2) 1 — — 7 Less: collateral held/posted (3) — — — (7) Total net derivative assets/liabilities $ 1 $ — $ — $ — (1) The foreign exchange forward contracts have notional amounts of EUR 6 million, GBP 6 million, SGD 1 million and INR 596 million as of December 31, 2020, and notional amounts of EUR 9 million, GBP 14 million, SGD 1 million and INR 596 million as of December 31, 2019. (2) In addition to the derivatives disclosed in the table, the Company enters into forward contracts to purchase when-issued mortgage-backed securities as part of its community reinvestment initiatives. At December 31, 2020, the Company had one outstanding contract with a total notional amount of $27 million and immaterial fair value. At December 31, 2019, the Company had two outstanding contracts with a total notional amount of $42 million and immaterial fair value. (3) Collateral amounts, which consist of both cash and investment securities, are limited to the related derivative asset/liability balance and do not include excess collateral received/pledged. The following amounts were recorded on the statements of financial condition related to cumulative basis adjustments for fair value hedges (dollars in millions): December 31, 2020 December 31, 2019 Carrying Amount of Hedged Assets/Liabilities Cumulative Amount of Fair Value Hedging Adjustment Increasing the Carrying Amount of Hedged Assets/Liabilities Carrying Amount of Hedged Assets/Liabilities Cumulative Amount of Fair Value Hedging Adjustment Increasing the Carrying Amount of Hedged Assets/Liabilities Long-term borrowings $ 11,881 $ 281 $ 14,244 $ 13 The following table summarizes the impact of the derivative instruments on income and indicates where within the consolidated financial statements such impact is reported (dollars in millions): Location and Amount of (Losses) Gains Recognized in Income Interest Expense Other Income Deposits Long-Term Borrowings For the Year Ended December 31, 2020 Total amounts of income and expense line items presented in the statements of income in which the effects of fair value or cash flow hedges are recorded $ (1,231) $ (602) $ 56 The effects of cash flow and fair value hedging (Losses) Gains on cash flow hedging relationship Amounts reclassified from OCI into earnings $ (9) $ (3) $ — Gains (losses) on fair value hedging relationships Gains (losses) on hedged items $ — $ (268) $ — Gains on interest rate swaps — 423 — Total gains on fair value hedges $ — $ 155 $ — For the Year Ended December 31, 2019 Total amounts of income and expense line items presented in the statements of income in which the effects of fair value or cash flow hedges are recorded $ (1,587) $ (943) $ 93 The effects of cash flow and fair value hedging Gains on cash flow hedging relationship Amounts reclassified from OCI into earnings $ 3 $ 2 $ — Gains (losses) on fair value hedging relationships Gains (losses) on hedged items $ — $ (104) $ — Gains on interest rate swaps — 72 — Total gains (losses) on fair value hedges $ — $ (32) $ — The effects of derivatives not designated in hedging relationships Gains (losses) on derivatives not designated as hedges $ — $ — $ (1) Location and Amount of (Losses) Gains Recognized in Income Interest Expense Deposits Long-Term Borrowings Other Income For the Year Ended December 31, 2018 Total amounts of income and expense line items presented in the statements of income in which the effects of fair value or cash flow hedges are recorded $ (1,238) $ (901) $ 97 The effects of cash flow and fair value hedging Gains on cash flow hedging relationship Amounts reclassified from OCI into earnings $ — $ 6 $ — Gains (losses) on fair value hedging relationship Gains (losses) on hedged items $ — $ (18) $ — Gains (losses) on interest rate swaps — (23) — Total gains (losses) on fair value hedges $ — $ (41) $ — The effects of derivatives not designated in hedging relationships Gains on derivatives not designated as hedges $ — $ — $ 1 For the impact of the derivative instruments on OCI, see Note 13: Accumulated Other Comprehensive Income. Collateral Requirements and Credit-Risk Related Contingency Features The Company has master netting arrangements and minimum collateral posting thresholds with its counterparties for its fair value and cash flow hedge interest rate swaps and foreign exchange forward contracts. The Company has not sought a legal opinion in relation to the enforceability of its master netting arrangements and, as such, does not report any of these positions on a net basis. Collateral is required by either the Company or its subsidiaries or the counterparty depending on the net fair value position of these derivatives held with that counterparty. The Company may also be required to post collateral with a counterparty for its fair value and cash flow hedge interest rate swaps depending on the credit rating it or Discover Bank receives from specified major credit rating agencies. These collateral receivable or payable amounts are generally not offset against the fair value of these derivatives, but are recorded separately in other assets or deposits. Most of the Company’s cash collateral amounts relate to positions cleared through an exchange and are reflected as offsets to the associated derivatives balances recorded in other assets and accrued expenses and other liabilities. At December 31, 2020, Discover Bank’s credit rating met specified thresholds set by its counterparties. However, if its credit rating is reduced below investment grade, Discover Bank would be required to post additional collateral. The amount of additional collateral as of December 31, 2020, would have been $0 million. DFS (Parent Company) had no outstanding derivatives as of December 31, 2020, and therefore, no collateral was required. The Company also has agreements with certain of its derivative counterparties that contain a provision where if the Company defaults on any of its indebtedness, including default where repayment of the indebtedness has not been accelerated by the lender, then the Company could also be declared in default on its derivative obligations.

Segment Disclosures

Segment Disclosures	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Segment Disclosures	Segment Disclosures The Company’s business activities are managed in two segments: Digital Banking and Payment Services. • Digital Banking: The Digital Banking segment includes Discover-branded credit cards issued to individuals on the Discover Network and other consumer products and services, including private student loans, personal loans, home loans and other consumer lending and deposit products. The majority of Digital Banking revenues relate to interest income earned on the segment’s loan products. Additionally, the Company’s credit card products generate substantially all revenues related to discount and interchange, protection products and loan fee income. • Payment Services: The Payment Services segment includes PULSE, an automated teller machine, debit and electronic funds transfer network; Diners Club, a global payments network; and the Company’s Network Partners business, which provides payment transaction processing and settlement services on the Discover Network. The majority of Payment Services revenues relate to transaction processing revenue from PULSE and royalty and licensee revenue from Diners Club. The business segment reporting provided to and used by the Company’s chief operating decision maker is prepared using the following principles and allocation conventions: • The Company aggregates operating segments when determining reportable segments. • Corporate overhead is not allocated between segments; all corporate overhead is included in the Digital Banking segment. • Through its operation of the Discover Network, the Digital Banking segment incurs fixed marketing, servicing and infrastructure costs that are not specifically allocated among the segments, with the exception of an allocation of direct and incremental costs driven by the Company’s Payment Services segment. • The assets of the Company are not allocated among the operating segments in the information reviewed by the Company’s chief operating decision maker. • The revenues of each segment are derived from external sources. The segments do not earn revenue from intercompany sources. • Income taxes are not specifically allocated between the operating segments in the information reviewed by the Company’s chief operating decision maker. The following table presents segment data (dollars in millions): Digital Payment Total For the Year Ended December 31, 2020 Interest income Credit card loans $ 8,985 $ — $ 8,985 Private student loans 754 — 754 Personal loans 958 — 958 Other 398 — 398 Total interest income 11,095 — 11,095 Interest expense 1,865 — 1,865 Net interest income 9,230 — 9,230 Provision for credit losses 5,134 — 5,134 Other income 1,459 399 1,858 Other expense 4,292 227 4,519 Income before income tax expense $ 1,263 $ 172 $ 1,435 For the Year Ended December 31, 2019 Interest income Credit card loans $ 9,690 $ — $ 9,690 Private student loans 817 — 817 Personal loans 983 — 983 Other 502 1 503 Total interest income 11,992 1 11,993 Interest expense 2,530 — 2,530 Net interest income 9,462 1 9,463 Provision for credit losses (1) 3,233 (2) 3,231 Other income 1,648 348 1,996 Other expense 4,231 162 4,393 Income before income tax expense $ 3,646 $ 189 $ 3,835 For the Year Ended December 31, 2018 Interest income Credit card loans $ 8,835 $ — $ 8,835 Private student loans 753 — 753 Personal loans 935 — 935 Other 369 1 370 Total interest income 10,892 1 10,893 Interest expense 2,139 — 2,139 Net interest income 8,753 1 8,754 Provision for credit losses (1) 3,035 — 3,035 Other income 1,645 310 1,955 Other expense 3,918 159 4,077 Income before income tax expense $ 3,445 $ 152 $ 3,597 (1) Prior to the adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach.

Revenue from Contracts with Cus

Revenue from Contracts with Customers	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers	Revenue from Contracts with Customers ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”), generally applies to the sales of any good or service for which no other specific accounting guidance is provided. ASC 606 defines a principles-based model under which revenue from a contract is allocated to the distinct performance obligations within the contract and recognized in income as each performance obligation is satisfied. The Company’s revenue that is subject to this model includes discount and interchange, protection products fees, transaction processing revenue and amounts classified as other income. The following table presents revenue from contracts with customers disaggregated by business segment and reconciles revenue from contracts with customers to total other income (dollars in millions): Digital Payment Total For the Year Ended December 31, 2020 Other income subject to ASC 606 Discount and interchange revenue, net (1) $ 871 $ 62 $ 933 Protection products revenue 180 — 180 Transaction processing revenue — 195 195 Other (loss) income (7) 63 56 Total other income subject to ASC 606 (2) 1,044 320 1,364 Other income not subject to ASC 606 Loan fee income 414 — 414 Other income 1 79 80 Total other income not subject to ASC 606 415 79 494 Total other income by operating segment $ 1,459 $ 399 $ 1,858 For the Year Ended December 31, 2019 Other income subject to ASC 606 Discount and interchange revenue, net (1) $ 1,000 $ 66 $ 1,066 Protection products revenue 194 — 194 Transaction processing revenue — 197 197 Other income 8 85 93 Total other income subject to ASC 606 (2) 1,202 348 1,550 Other income not subject to ASC 606 Loan fee income 449 — 449 Other (loss) income (3) — (3) Total other income not subject to ASC 606 446 — 446 Total other income by operating segment $ 1,648 $ 348 $ 1,996 For the Year Ended December 31, 2018 Other income subject to ASC 606 Discount and interchange revenue, net (1) $ 1,022 $ 52 $ 1,074 Protection products revenue 204 — 204 Transaction processing revenue — 178 178 Other income 17 80 97 Total other income subject to ASC 606 (2) 1,243 310 1,553 Other income not subject to ASC 606 Loan fee income 402 — 402 Total other income not subject to ASC 606 402 — 402 Total other income by operating segment $ 1,645 $ 310 $ 1,955 (1) Net of rewards, including Cashback Bonus rewards, of $1.9 billion, $1.9 billion and $1.8 billion for the years ended December 31, 2020, 2019 and 2018, respectively. (2) Excludes $2 million, $3 million and $3 million deposit product fees that are reported within net interest income for the years ended December 31, 2020, 2019 and 2018, respectively. For a detailed description of the Company’s significant revenue recognition accounting policies, see Note 2: Summary of Significant Accounting Policies.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	Related Party TransactionsIn the ordinary course of business, the Company offers consumer financial products to its directors, executive officers and certain members of their families. These products are offered on substantially the same terms as those prevailing at the time for comparable transactions with unrelated parties and these receivables are included in the loan receivables in the Company’s consolidated statements of financial condition. They were not material to the Company’s financial position or results of operations.

Parent Company Condensed Financ

Parent Company Condensed Financial Information	12 Months Ended
	Dec. 31, 2020
Condensed Financial Information Disclosure [Abstract]
Parent Company Condensed Financial Information	Parent Company Condensed Financial Information The following Parent Company financial statements are provided in accordance with SEC rules, which require such disclosure when the restricted net assets of consolidated subsidiaries exceed 25% of consolidated net assets. Discover Financial Services (Parent Company Only) Condensed Statements of Financial Condition December 31, 2020 2019 (dollars in millions) Assets Cash and cash equivalents (1) $ 2,802 $ 2,511 Restricted cash 20 20 Notes receivable from subsidiaries (2) 891 877 Investments in bank subsidiaries 10,188 11,319 Investments in non-bank subsidiaries 727 820 Other assets 567 600 Total assets $ 15,195 $ 16,147 Liabilities and Stockholders’ Equity Non-interest bearing deposit accounts $ 2 $ 2 Short-term borrowings from subsidiaries 283 283 Long-term borrowings 3,673 3,636 Accrued expenses and other liabilities 353 367 Total liabilities 4,311 4,288 Stockholders’ equity 10,884 11,859 Total liabilities and stockholders’ equity $ 15,195 $ 16,147 (1) The Parent Company had $2.7 billion and $2.4 billion in a money market deposit account at Discover Bank as of December 31, 2020 and 2019, respectively, which is included in cash and cash equivalents. These funds are available to the Parent for liquidity purposes. (2) The Parent Company advanced $500 million to Discover Bank as of December 31, 2020 and 2019, which is included in notes receivable from subsidiaries. These funds are available to the Parent for liquidity purposes. Discover Financial Services (Parent Company Only) Condensed Statements of Income For the Years Ended December 31, 2020 2019 2018 (dollars in millions) Interest income $ 44 $ 82 $ 67 Interest expense 205 212 189 Net interest expense (161) (130) (122) Dividends from bank subsidiaries 555 2,530 2,375 Dividends from non-bank subsidiaries 200 100 450 Total income 594 2,500 2,703 Other expense (16) 1 — Income before income tax benefit and equity in undistributed net income of subsidiaries 610 2,499 2,703 Income tax benefit 30 25 33 Equity in undistributed net income of subsidiaries 501 433 6 Net income 1,141 2,957 2,742 Other comprehensive income, net 164 37 25 Comprehensive income $ 1,305 $ 2,994 $ 2,767 Discover Financial Services (Parent Company Only) Condensed Statements of Cash Flows For the Years Ended December 31, 2020 2019 2018 (dollars in millions) Cash flows provided by operating activities Net income $ 1,141 $ 2,957 $ 2,742 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed net income of subsidiaries (501) (433) (6) Stock-based compensation expense 42 69 81 Deferred income taxes (5) (8) (5) Depreciation and amortization 41 38 34 Changes in assets and liabilities: Decrease (increase) in other assets 42 92 (416) (Decrease) increase in other liabilities and accrued expenses (30) 50 (129) Net cash provided by operating activities 730 2,765 2,301 Cash flows used for investing activities Decrease (increase) in investment in subsidiaries — — (3) Increase in loans to subsidiaries (15) (55) (62) Net cash used for investing activities (15) (55) (65) Cash flows used for financing activities Net increase (decrease) in short-term borrowings from subsidiaries — 42 (110) Proceeds from issuance of common stock 10 7 6 Proceeds from issuance of long-term borrowings — 595 49 Maturities and repayment of long-term borrowings (3) (86) (6) Purchases of treasury stock (348) (1,768) (2,065) Net increase (decrease) in deposits — (2) 1 Proceeds from issuance of preferred stock 493 — — Dividends paid on common and preferred stock (576) (573) (552) Net cash used for financing activities (424) (1,785) (2,677) Increase (decrease) in cash, cash equivalents and restricted cash 291 925 (441) Cash, cash equivalents and restricted cash, at beginning of period 2,531 1,606 2,047 Cash, cash equivalents and restricted cash, at end of period $ 2,822 $ 2,531 $ 1,606 Reconciliation of cash, cash equivalents and restricted cash Cash and cash equivalents $ 2,802 $ 2,511 $ 1,586 Restricted cash 20 20 20 Cash, cash equivalents and restricted cash, at end of period $ 2,822 $ 2,531 $ 1,606 Supplemental disclosure of cash flow information Cash paid during the period for: Interest expense $ 168 $ 170 $ 156 Income taxes, net of income tax refunds $ (31) $ 20 $ (22)

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	Subsequent EventsThe Company has evaluated events and transactions that have occurred subsequent to December 31, 2020, and determined that there were no subsequent events that would require recognition or disclosure in the consolidated financial statements.

Quarterly Results

Quarterly Results	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Data [Abstract]
Quarterly Results	Quarterly Results The following table provides unaudited quarterly results (dollars in millions, except per share data): December 31, 2020 September 30, 2020 June 30, 2020 March 31, 2020 December 31, 2019 September 30, 2019 June 30, 2019 March 31, 2019 Interest income $ 2,760 $ 2,681 $ 2,672 $ 2,982 $ 3,039 $ 3,040 $ 2,977 $ 2,937 Interest expense 383 416 482 584 615 638 645 632 Net interest income 2,377 2,265 2,190 2,398 2,424 2,402 2,332 2,305 Provision for credit losses 531 750 2,046 1,807 836 799 787 809 Other income 447 449 472 490 520 498 520 458 Other expense 1,278 1,005 1,077 1,159 1,184 1,107 1,078 1,024 Income (loss) before income tax expense 1,015 959 (461) (78) 924 994 987 930 Income tax expense (benefit) 216 188 (93) (17) 216 224 234 204 Net income (loss) $ 799 $ 771 $ (368) $ (61) $ 708 $ 770 $ 753 $ 726 Net income (loss) allocated to common stockholders (1) $ 794 $ 751 $ (369) $ (78) $ 704 $ 749 $ 747 $ 705 Basic earnings (loss) per common share (1) $ 2.59 $ 2.45 $ (1.20) $ (0.25) $ 2.25 $ 2.36 $ 2.32 $ 2.15 Diluted earnings (loss) per common share (1) $ 2.59 $ 2.45 $ (1.20) $ (0.25) $ 2.25 $ 2.36 $ 2.32 $ 2.15 (1) Because the inputs to net income allocated to common stockholders and earnings per share are calculated using weighted averages for the quarter, the sum of all four quarters may differ from the year to date amounts in the consolidated statements of income.

Background and Basis of Prese_2

Background and Basis of Presentation (Policies)	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Significant Accounting Policies	Basis of PresentationThe accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”).
Use of Estimates	The preparation of financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and related disclosures. These estimates are based on information available as of the date of the consolidated financial statements. The Company believes that the estimates used in the preparation of the consolidated financial statements are reasonable. Actual results could differ from these estimates.
Consolidation	Principles of Consolidation The accompanying consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. The Company’s policy is to consolidate all entities in which it owns more than 50% of the outstanding voting stock unless it does not control the entity. However, the Company did not have a controlling voting interest in any entity other than its wholly-owned subsidiaries in the periods presented in the accompanying consolidated financial statements. It is also the Company’s policy to consolidate any VIEs for which the Company is the primary beneficiary, as defined by GAAP. On this basis, the Company consolidates the Discover Card Master Trust I (“DCMT”) and the Discover Card Execution Note Trust (“DCENT”) as well as the student loan securitization trust. The Company is deemed to be the primary beneficiary of each of these trusts since it is, for each, the trust Servicer and the holder of both the residual interest and the majority of the most subordinated interests. Because of those involvements, the Company has, for each trust, (i) the power to direct the activities that most significantly impact the economic performance of the trust and (ii) the obligation (or right) to absorb losses (or receive benefits) of the trust that could potentially be significant. The Company has determined that it was not the primary beneficiary of any other VIE during the years ended December 31, 2020, 2019 and 2018. For investments in any entities in which the Company owns 50% or less of the outstanding voting stock but in which the Company has significant influence over operating and financial decisions, the Company applies the equity method of accounting. The Company also applies the equity method to its investments in qualified affordable housing projects and similar tax credit partnerships. In cases where the Company’s equity investment is less than 20% and significant influence does not exist, such investments are carried at cost as they typically do not have readily determinable fair values, and are adjusted for any impairment in value.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Cash and Cash Equivalents	Cash and Cash EquivalentsCash and cash equivalents is defined by the Company as cash on deposit with banks, including time deposits and other highly liquid investments, with maturities of 90 days or less when purchased, excluding amounts restricted by certain contractual or other obligations. Cash and cash equivalents included $1.1 billion and $959 million of cash and due from banks and $12.5 billion and $6.0 billion of interest-earning deposits at other banks at December 31, 2020 and 2019, respectively.
Restricted Cash	Restricted CashRestricted cash includes cash for which the Company’s ability to withdraw funds at any time is contractually limited. Restricted cash is generally designated for specific purposes arising out of certain contractual or other obligations.
Investment Securities	Investment Securities At December 31, 2020, investment securities consisted of United States Treasury obligations and mortgage-backed securities issued by government agencies. Investment securities that the Company has the positive intent and ability to hold to maturity are classified as held-to-maturity and are reported at amortized cost. All other investment securities are classified as available-for-sale, as the Company does not hold investment securities for trading purposes. Available-for-sale investment securities are reported at fair value with unrealized gains and losses, net of tax, reported as a component of accumulated other comprehensive income (“AOCI”) included in stockholders’ equity. The Company estimates the fair value of available-for-sale investment securities as more fully discussed in Note 20: Fair Value Measurements. The amortized cost for each held-to-maturity and available-for-sale investment security is adjusted for amortization of premiums or accretion of discounts, as appropriate. Such amortization or accretion is included in interest income. The United States Treasury obligations and residential mortgage-backed securities issued by government agencies in which the Company invests have long histories with no credit losses and are explicitly or implicitly guaranteed by the United States government. Therefore, management has concluded that there is no expectation of non-payment on its investment securities and does not record an allowance for credit losses on these investments.
Loan Receivables	Loan Receivables Loan receivables consist of credit card receivables and other loan receivables. Loan receivables also include unamortized net deferred loan origination fees and costs (also see “— Significant Revenue Recognition Accounting Policies — Loan Interest and Fee Income”). Credit card loan receivables are reported at their principal amounts outstanding and include uncollected billed interest and fees and are reduced for unearned revenue related to balance transfer fees (also see “— Significant Revenue Recognition Accounting Policies — Loan Interest and Fee Income”). Other loans consist of private student loans, personal loans and other loans and are reported at their principal amounts outstanding. For private student loans, principal amounts outstanding also include accrued interest that has been capitalized. The Company’s loan receivables are deemed to be held for investment at origination or acquisition because management has the intent and ability to hold them for the foreseeable future. Cash flows associated with loans originated or acquired for investment are classified as cash flows from investing activities, regardless of a subsequent change in intent.
Delinquent Loans and Charge-Offs	Delinquent Loans and Charge-Offs The entire balance of an account is contractually past due if the minimum payment is not received by the specified date on the customer’s billing statement. Delinquency is reported on loans that are 30 days or more past due. Credit card loans are charged off at the end of the month during which an account becomes 180 days past due. Closed-end unsecured consumer loan receivables are charged off at the end of the month during which an account becomes 120 days contractually past due. Customer bankruptcies and probate accounts are charged off by the end of the month 60 days following the receipt of notification of the bankruptcy or death, but not later than the 180-day or 120-day time frame described above. Receivables associated with alleged or potential fraudulent transactions are adjusted to their net realizable value upon receipt of notification of such fraud through a charge to other expense and are subsequently written off at the end of the month 90 days following notification, but not later than the contractual 180-day or 120-day time frame described above. The Company’s charge-off policies are designed to comply with guidelines established by the Federal Financial Institutions Examination Council (“FFIEC”). The Company’s net charge-offs include the principal amount of loans charged off less principal recoveries and exclude charged-off interest and fees, recoveries of interest and fees and fraud losses.
Allowance for Credit Losses	Allowance for Credit Losses The Company maintains an allowance for credit losses at a level that is appropriate to absorb net credit losses anticipated over the remaining expected life of loan receivables as of the balance sheet date. The estimate of expected credit losses considers uncollectible principal, interest and fees associated with the Company's loan receivables existing as of the balance sheet date. Additionally, the estimate includes expected recoveries of amounts that were either previously charged off or are expected to be charged off. The allowance is evaluated quarterly for appropriateness and is maintained through an adjustment to the provision for credit losses. Charge-offs of principal amounts of loans outstanding are deducted from the allowance and subsequent recoveries of such amounts increase the allowance. Charge-offs of loan balances representing unpaid interest and fees result in a reversal of interest and fee income, respectively, which is effectively a reclassification of the provision for credit losses. The Company calculates its allowance for credit losses by estimating expected credit losses separately for classes of receivables with similar risk characteristics. This results in segmenting the portfolio by loan product type, which is the level that the Company develops and documents its methodology for determining the allowance for credit losses. The estimate of expected credit losses for each loan product type is based on: (i) a reasonable and supportable forecast period; (ii) a reversion period; and (iii) a post-reversion period based on historical information covering the remaining life of the loan, all of which is netted with expected recoveries. The lengths of the reasonable and supportable forecast and reversion periods can vary and are subject to a quarterly assessment that considers the economic outlook and level of variability among macroeconomic forecasts. Generally, a straight-line method is used to revert from the reasonable and supportable forecast period to the post-reversion period, but in certain stressed scenarios, a weighted approach may be deemed more appropriate. Several analyses are used to help estimate credit losses anticipated over the remaining expected life of loan receivables as of the balance sheet date. The Company's estimation process includes models that predict customer losses based on risk characteristics and portfolio attributes, macroeconomic variables and historical data and analysis. There is a significant amount of judgment applied in selecting inputs and analyzing the results produced by the models to determine the allowance. For credit card loans, the Company uses a modeling framework that includes the following components for estimating expected credit losses: • Probability of default: this component estimates the probability of charge-off at different points in time over the life of each loan. • Exposure at default: this component estimates the portion of the balance sheet date balance remaining at any given time of charge-off for each loan. Given that there is no stated life of a receivable balance on a revolving credit card account, the Company applies a percentage of expected payments to estimate the portion of the balance that would remain at the time of charge-off. • Loss given default: this component estimates the percentage of exposure (i.e., net loss) at time of charge-off that cannot be recovered, with the offsetting forecast recoveries being the driver of this estimate. • Recoveries from previously charged-off accounts are estimated separately and are netted as part of the aggregation of all of the components of the card loss modeling framework. For private student loans and personal loans, the Company uses vintage-based models that estimate expected credit losses over the life of the loan, net of recovery estimates, impacted mainly by time elapsed since origination, credit quality of origination vintages and macroeconomic forecasts. The components described above for credit card, private student and personal loans are developed utilizing historical data and applicable macroeconomic variable inputs based on statistical analysis and customer behavioral relationships with credit performance. Expected recoveries from loans charged off as of the balance sheet date are modeled separately and included in the allowance estimate. The Company leverages these models and recent macroeconomic forecasts for the portion of the estimate associated with the reasonable and supportable forecast period. To estimate expected credit losses for the remainder of the life of the credit card loans, the Company reverts to historical experience of credit card loans with characteristics similar to those as of the balance sheet date and observed over various phases of a credit cycle. To estimate expected credit losses for the remainder of the life of private student and personal loans, the Company reverts to use of average macroeconomic variables over an appropriate historical period. The considerations in these models include past and current loan performance, loan growth and seasoning, risk management practices, account collection strategies, economic conditions, bankruptcy filings, policy changes and forecasting uncertainties. Consideration of past and current loan performance includes the post-modification performance of loans modified in a troubled debt restructuring. For the credit card loan portfolio, the Company estimates its credit losses on a loan-level basis, which includes loans that are delinquent and/or no longer accruing interest and/or loans that have been restructured. For the remainder of its portfolio, including private student, personal and other loans, the Company estimates its credit losses on a pooled basis. For all loan types, recoveries are estimated at a pooled level based on estimates of future cash flows derived using historical experience. Accrued interest receivable on credit card loans is included in the estimate of expected credit losses once billed to the customer (i.e., once the interest becomes part of the loan balance). Except as noted in the following sentence, an allowance for credit losses is not recorded for unbilled credit card interest or accrued interest receivable on other loan classes as the impact to the allowance for credit losses is not material. Accrued interest receivable on student loans that have not yet entered repayment is included in the estimate of expected credit losses. No liability for expected credit losses is required for unused lines of credit on the Company’s credit card loans because they are unconditionally cancellable. The Company records a liability for expected credit losses for unfunded commitments on all other loans, which is presented as part of accrued expenses and other liabilities in the consolidated statements of financial condition. This liability is evaluated quarterly for appropriateness and is maintained through an adjustment to the provision for credit losses. As part of certain collection strategies, the Company may modify the terms of loans to customers experiencing financial hardship. Temporary and permanent modifications on credit card and personal loans, as well as temporary modifications on private student loans and certain grants of private student loan forbearance are accounted for as troubled debt restructurings. The Company classifies a modified loan in which a concession has been granted to the borrower as a troubled debt restructuring based on the cumulative length of the concession period and credit quality of the borrower. Loan receivables that have been modified are subject to the same requirements for the accrual of expected credit loss over their expected remaining lives as described above for unmodified loans. The effects of all loan modifications, including TDRs, loan modifications exempt from TDR status pursuant to the Coronavirus Aid, Relief, and Economic Security Act ("CARES Act”) and Skip-a-Pay (payment deferral) programs, are reflected in the allowance for credit losses. An adjustment to the allowance for credit losses is not recorded for reasonably expected TDRs as the impact is not material. When the impact of the concession can only be captured by use of a discounted cash flow method (or a reconcilable method), such method is used to measure the allowance for credit losses.
Premises and Equipment, net	Premises and Equipment, net Premises and equipment, net, are stated at cost less provisions for impairment and accumulated depreciation and amortization. Accumulated depreciation and amortization is computed using the straight-line method over the estimated useful lives of the assets. The Company periodically reviews the estimated useful lives and may adjust them as necessary. Buildings are depreciated over a period of thirty-nine years. The costs of improvements are capitalized and depreciated either over the asset’s estimated useful life, typically ten years to fifteen years, or over the remaining term of the lease, when applicable. Furniture and fixtures are depreciated over a period of five years to ten years. Equipment is depreciated over three years to ten years. Maintenance and repairs are immediately expensed when incurred, while the costs of significant improvements are capitalized. Purchased software and capitalized costs related to internally developed software are amortized over their useful lives of three years to ten years. Costs incurred during the application development stage related to internally developed software are capitalized. Costs are expensed as incurred during the preliminary project stage and post implementation stage. Once the capitalization criteria as defined in GAAP have been met, external direct costs incurred for materials and services used in developing or obtaining internal-use computer software and payroll and payroll-related costs for employees who are directly associated with the internal-use computer software project (to the extent those employees devoted time directly to the project) are capitalized. Amortization of capitalized costs begins when the software is ready for its intended use. Capitalized software is included in premises and equipment, net in the Company’s consolidated statements of financial condition. See Note 6: Premises and Equipment for further information about the Company’s premises and equipment. Cloud computing arrangements involving the licensing of software that meet certain criteria are recognized as the acquisition of software. Such assets are measured at the present value of the license obligation, if the license is to be paid over time, in addition to any capitalized upfront costs and amortized over the life of the arrangement. Cloud computing arrangements that do not meet the criteria to be recognized as acquired software are accounted for as service contracts. To date, none of the Company’s cloud computing arrangements have met the criteria to be recognized as acquired software. Premises and equipment are subject to impairment testing when events or conditions indicate that the carrying value of the asset may not be fully recoverable from future cash flows. See “— Intangible Assets” for additional details on impairment testing.
Goodwill	Goodwill Goodwill is recorded as part of the Company’s acquisitions of businesses when the purchase price exceeds the fair value of the net tangible and separately identifiable intangible assets acquired. The Company’s goodwill is not
Intangible Assets	Intangible Assets The Company’s identifiable intangible assets consist of both amortizable and non-amortizable intangible assets. The Company’s amortizable intangible assets consist primarily of acquired customer relationships and certain trade name intangibles. All of the Company’s amortizable intangible assets are carried at net book value and are amortized over their estimated useful lives. The amortization periods approximate the periods over which the Company expects to generate future net cash inflows from the use of these assets. The Company’s policy is to amortize intangibles in a manner that reflects the pattern in which the projected net cash inflows to the Company are expected to occur, where such pattern can be reasonably determined, as opposed to the straight-line basis. This method of amortization typically results in a greater portion of the intangible asset being amortized in the earlier years of its useful life. All of the Company’s amortizable intangible assets, as well as other amortizable or depreciable long-lived assets such as premises and equipment, are subject to impairment testing when events or conditions indicate that the carrying value of the asset may not be fully recoverable from future cash flows. A test for recoverability is done by comparing the asset’s carrying value to the sum of the undiscounted future net cash inflows expected to be generated from the use of the asset over its remaining useful life. Impairment exists if the sum of the undiscounted expected future net cash inflows is less than the carrying amount of the asset. Impairment would result in a write-down of the asset to its estimated fair value. The estimated fair values of these assets are based on the discounted present value of the stream of future net cash inflows expected to be derived over the remaining useful lives of the assets. If an impairment write-down is recorded, the remaining useful life of the asset will be evaluated to determine whether revision of the remaining amortization or depreciation period is appropriate. The Company’s non-amortizable intangible assets consist primarily of the brand-related intangibles and international transaction processing rights included in the acquisition of Diners Club. These assets are deemed to have indefinite useful lives and are therefore not subject to amortization. All of the Company’s non-amortizable intangible assets are subject to a test for impairment annually as of October 1, or more frequently if events or changes in circumstances indicate that the asset might be impaired. As required by GAAP, if the carrying value of a non-amortizable intangible asset is in excess of its fair value, the asset must be written down to its fair value through the recognition of an impairment charge to earnings. In contrast to amortizable intangibles, there is no test for recoverability associated with the impairment test for non-amortizable intangible assets. No significant impairment concerns were identified during the annual impairment test conducted as of October 1, 2020. See Note 7: Goodwill and Intangibles for additional details on the Company’s intangible assets.
Stock-based Compensation	Stock-based CompensationThe Company measures the cost of employee services received in exchange for an award of stock-based compensation based on the grant-date fair value of the award. The cost, net of estimated forfeitures, is recognized over the requisite service period. Awards to employees who are retirement-eligible at any point during the year are amortized over 12 months in accordance with the vesting terms that apply under those circumstances. No compensation cost is recognized for awards that are subsequently forfeited.
Advertising Costs	Advertising CostsThe Company expenses television and radio advertising costs in the period in which the advertising is first aired and all other advertising costs as incurred. Advertising costs are recorded in marketing and business development and were $212 million, $264 million and $258 million for the years ended December 31, 2020, 2019 and 2018, respectively.
Income Taxes	Income TaxesIncome tax expense is provided for using the asset and liability method, under which deferred tax assets and liabilities are determined based on the temporary differences between the financial reporting and income tax bases of assets and liabilities using currently enacted tax rates. Deferred tax assets are recognized when their realization is determined to be more likely than not. A valuation allowance is provided if the Company believes it is more likely than not that all or some portion of the deferred tax asset will not be realized. An increase or decrease in the valuation allowance that results in a change in circumstances and which causes a change in management’s judgement about the realizability of the related deferred tax asset is included in the current tax provision. Uncertain tax positions are measured at the highest amount of tax benefit for which realization is judged to be more likely than not. Tax benefits that do not meet these criteria are unrecognized tax benefits. The Company recognizes and reports interest and penalties, if necessary, related to uncertain tax positions within its provision for income tax expense. See Note 15: Income Taxes for more information about the Company’s income taxes.
Accumulated Other Comprehensive Income	Accumulated Other Comprehensive IncomeThe Company records unrealized gains and losses on available-for-sale securities, changes in the fair value of cash flow hedges and certain pension and foreign currency translation adjustments in other comprehensive income (“OCI”) on an after-tax basis where applicable. The Company’s policy is to adjust the tax effects of a component of AOCI in the same period in which the item is sold or otherwise derecognized, or when the carrying value of the item is remeasured. Details of OCI, net of tax, are presented in the statement of comprehensive income and a rollforward of AOCI is presented in the consolidated statements of changes in stockholders’ equity and Note 13: Accumulated Other Comprehensive Income.
Significant Revenue Recognition Accounting Policies, Loan Interest and Fee Income	Significant Revenue Recognition Accounting Policies Loan Interest and Fee Income Interest on loans is comprised largely of interest on credit card loans and is recognized based on the amount of loans outstanding and their contractual interest rate. Interest on credit card loans is included in loan receivables when billed to the customer. The Company accrues unbilled interest revenue each month from a customer’s billing cycle date to the end of the month. The Company applies an estimate of the percentage of loans that will revolve in the next cycle in the estimation of the accrued unbilled portion of interest revenue that is included in accrued interest receivable on the consolidated statements of financial condition. Interest on other loan receivables is accrued each month in accordance with their contractual terms and recorded in accrued interest receivable, which is included in other assets in the consolidated statements of financial condition. The Company recognizes fees (except balance transfer fees and certain product fees) on loan receivables in interest income or loan fee income as the fees are assessed. Balance transfer fees and certain product fees are recognized in interest income or loan fee income ratably over the periods to which they relate. Balance transfer fees are accreted to interest income over the estimated life of the related balance. As of December 31, 2020 and 2019, deferred revenues related to balance transfer fees, recorded as a reduction of loan receivables, were $62 million and $67 million, respectively. Loan fee income consists of fees on credit card loans and includes late, cash advance, returned check and other miscellaneous fees and is reflected net of waivers and charge-offs. Direct loan origination costs on credit card loans are deferred and amortized on a straight-line basis over a one year period and recorded in interest income from credit card loans. Direct loan origination costs on other loan receivables are deferred and amortized over the life of the loan using the interest method and are recorded in interest income from other loans. As of December 31, 2020 and 2019, the remaining unamortized deferred costs related to loan origination were $157 million and $178 million, respectively, and were recorded in loan receivables. The Company accrues interest and fees on loan receivables until the loans are paid or charged off, except in instances of customer bankruptcy, death or fraud, where no further interest and fee accruals occur following notification. Credit card and closed-end consumer loan receivables are placed on non-accrual status upon receipt of notification of the bankruptcy or death of a customer or suspected fraudulent activity on an account. Upon completion of the fraud investigation, non-fraudulent credit card and closed-end consumer loan receivables may resume accruing interest. Payments received on non-accrual loans are allocated according to the same payment hierarchy applied to loans that are accruing interest. When loan receivables are charged off, unpaid accrued interest and fees are reversed against the income line items in which they were originally recorded in the consolidated statements of income. Charge-offs and recoveries of amounts that relate to capitalized interest on private student loans are treated as principal charge-offs and recoveries, affecting the provision for credit losses rather than interest income. The Company considers uncollectible interest and fee revenues in assessing the adequacy of the allowance for credit losses. Interest income from loans accounted for as troubled debt restructurings is accounted for in the same manner as other accruing loans. Cash collections on these loans are allocated according to the same payment hierarchy methodology applied to loans that are not in such programs.
Significant Revenue Recognition Accounting Policies, Other	Discount and Interchange Revenue The Company earns discount revenue from fees charged to merchants with whom it has entered into card acceptance agreements for processing credit card purchase transactions. The Company earns acquirer interchange revenue primarily from merchant acquirers on Discover Network, Diners Club and PULSE transactions made by credit and debit card customers at merchants with whom merchant acquirers have entered into card acceptance agreements for processing payment card transactions. These card acceptance arrangements generally renew automatically and do not have fixed durations. Under these agreements, the Company stands ready to process payment transactions as and when each is presented. The Company earns discount, interchange and similar fees only when transactions are processed. Contractually defined per-transaction fee amounts typically apply to each type of transaction processed and are recognized as revenue at the time each transaction is captured for settlement. These fees are typically collected by the Company as part of the process of settling transactions daily with merchants and acquirers and are fully earned at the time settlement is made. The Company pays issuer interchange to card-issuing entities that have entered into contractual arrangements to issue cards on the Discover Network and on certain transactions on the Diners Club and PULSE networks. This cost is contractually established and is based on the card-issuing organization’s transaction volume. The Company classifies this cost as a reduction of discount and interchange revenue. Costs of cardholder reward arrangements, including the Cashback Bonus reward program, are classified as reductions of discount and interchange revenue pursuant to guidance under Accounting Standards Codification (“ASC”) Topic 606 governing consideration payable to a customer. For both issuer interchange and cardholder rewards, the Company accrues the cost at the time each underlying card transaction is captured for settlement. Customer Rewards The Company offers its customers various reward programs, including the Cashback Bonus reward program, pursuant to which the Company pays certain customers a reward equal to a percentage of their credit card purchase amounts based on the type and volume of the customer’s purchases. The liability for customer rewards, which is included in accrued expenses and other liabilities on the consolidated statements of financial condition, is recorded on an individual customer basis and is accumulated as qualified customers earn rewards through their ongoing credit card purchase activity or other defined actions. The Company recognizes customer rewards costs as a reduction of the related revenue, if any. In instances where a reward is not associated with a revenue-generating transaction, such as when a reward is given for opening an account, the reward cost is recorded as an operating expense. For the years ended December 31, 2020, 2019 and 2018, rewards costs amounted to $1.9 billion, $1.9 billion and $1.8 billion, respectively. The liability for customer rewards was $1.7 billion at both December 31, 2020 and 2019, and is included in accrued expenses and other liabilities on the consolidated statements of financial condition. Protection Products Revenue The Company earns revenue related to fees received for ancillary products and services, including payment protection and identity theft protection services, to its credit card customers. A portion of this revenue comprises amounts earned for arranging for the delivery of products offered by third-party service providers. The amount of revenue recorded is generally based on either a percentage of a customer’s outstanding balance or a flat fee, in either case assessed monthly and recognized as earned. These contracts are month-to-month arrangements that are cancellable at any time. The Company recognizes each monthly fee in the period to which the service or coverage relates. Transaction Processing Revenue Transaction processing revenue represents switch fees charged to financial institutions and merchants under network participation agreements for processing ATM, debit and point-of-sale transactions over the PULSE network, as well as various participation and membership fees. Network participation agreements generally renew automatically and do not have fixed durations, although the Company does enter into fixed-term pricing or incentive arrangements with certain network participants. The impact of such incentives is not material to the Company’s consolidated statements of income. Similar to discount and interchange fees, switch fees are contractually defined per-transaction fee amounts and are assessed and recognized as revenue at the time each transaction is captured for settlement. These fees are typically collected by the Company as part of the process of settling transactions with network participants. Membership and other participation fees are recognized over the periods to which each fee relates. Other Income Other income includes sales-based royalty revenues earned by Diners Club, merchant fees, certain payments from merchants related to reward programs, revenues from network partners and other miscellaneous revenue items. Sales-based royalty revenues are recognized as the related sales are reported by Diners franchisees. All remaining items of other income are recognized as the related performance obligations are satisfied. Future Revenue Associated with Customer Contracts For contracts under which the Company processes payment card transactions, the Company has the right to assess fees for services performed and to collect those fees through the settlement process. The Company generates essentially all of its discount and interchange revenue and transaction processing revenue, as well as some revenue reported as other income, through such contracts. There is no specified quantity of service promised in these contracts as the number of payment transactions is dependent upon cardholder behavior, which is outside the control of the Company and its network customers (i.e., merchants, acquirers, issuers and other network participants). As noted above, these contracts are typically without fixed durations and renew automatically. For these reasons, the Company does not make or disclose an estimate of revenue associated with performance obligations attributable to the remaining terms of these contracts. Future revenue associated with the Company’s sales-based royalty revenues earned from Diners Club licensees is similarly variable and open-ended and therefore the Company does not make or disclose an estimate of royalties associated with performance obligations attributable to the remaining terms of the licensing and royalty arrangements. Because of the nature of the services and the manner of collection associated with the majority of the Company’s revenue from contracts with customers, material receivables or deferred revenues are not generated. Incentive Payments

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Schedule of Investment Securities	The Company’s other short-term investments and investment securities consist of the following (dollars in millions): December 31, 2020 2019 United States Treasury bills (1) $ 2,200 $ — Total other short-term investments $ 2,200 $ — United States Treasury securities (2) $ 9,354 $ 9,906 Residential mortgage-backed securities - Agency (3) 560 689 Total investment securities $ 9,914 $ 10,595 (1) Includes United States Treasury bills with maturity dates greater than 90 days but less than one year at the time of acquisition. (2) Includes $117 million and $121 million of United States Treasury securities pledged as swap collateral as of December 31, 2020 and 2019, respectively. (3) Consists of residential mortgage-backed securities issued by Fannie Mae, Freddie Mac and Ginnie Mae.
Schedule of Amortized Cost, Gross Unrealized Gains, Gross Unrealized Losses and Fair Value	The amortized cost, gross unrealized gains and losses and fair value of available-for-sale and held-to-maturity investment securities are as follows (dollars in millions): Amortized Gross Gross Fair Value At December 31, 2020 Available-for-Sale Investment Securities (1) United States Treasury securities $ 8,987 $ 367 $ — $ 9,354 Residential mortgage-backed securities - Agency 290 10 — 300 Total available-for-sale investment securities $ 9,277 $ 377 $ — $ 9,654 Held-to-Maturity Investment Securities (2) Residential mortgage-backed securities - Agency (3) $ 260 $ 9 $ — $ 269 Total held-to-maturity investment securities $ 260 $ 9 $ — $ 269 At December 31, 2019 Available-for-Sale Investment Securities (1) United States Treasury securities $ 9,759 $ 155 $ (8) $ 9,906 Residential mortgage-backed securities - Agency 414 3 — 417 Total available-for-sale investment securities $ 10,173 $ 158 $ (8) $ 10,323 Held-to-Maturity Investment Securities (2) Residential mortgage-backed securities - Agency (3) $ 272 $ 3 $ (1) $ 274 Total held-to-maturity investment securities $ 272 $ 3 $ (1) $ 274 (1) Available-for-sale investment securities are reported at fair value. (2) Held-to-maturity investment securities are reported at amortized cost. (3) Amounts represent residential mortgage-backed securities that were classified as held-to-maturity as they were entered into as a part of the Company’s community reinvestment initiatives.
Schedule of Fair Value of Securities in a Continuous Unrealized Loss Position for Less Than Twelve Months and More Than Twelve Months	The following table provides information about investment securities with aggregate gross unrealized losses and the length of time that individual investment securities have been in a continuous unrealized loss position (dollars in millions): Number of Securities in a Loss Position Less than 12 months More than 12 months Fair Unrealized Fair Unrealized At December 31, 2019 Available-for-Sale Investment Securities United States Treasury securities 11 $ 1,402 $ (8) $ — $ — Held-to-Maturity Investment Securities Residential mortgage-backed securities - Agency 58 $ 64 $ — $ 19 $ (1)
Schedule of Maturities and Weighted Average Yields of Available-for-Sale Debt Securities and Held-to-Maturity Debt Securities	Maturities and weighted-average yields of available-for-sale debt securities and held-to-maturity debt securities are provided in the tables below (dollars in millions): At December 31, 2020 One Year After One After Five After Ten Total Available-for-Sale Investment Securities—Amortized Cost United States Treasury securities $ 2,633 $ 6,354 $ — $ — $ 8,987 Residential mortgage-backed securities - Agency (1) — 45 235 10 290 Total available-for-sale investment securities $ 2,633 $ 6,399 $ 235 $ 10 $ 9,277 Held-to-Maturity Investment Securities—Amortized Cost Residential mortgage-backed securities - Agency (1) $ — $ — $ — $ 260 $ 260 Total held-to-maturity investment securities $ — $ — $ — $ 260 $ 260 Available-for-Sale Investment Securities—Fair Values United States Treasury securities $ 2,661 $ 6,693 $ — $ — $ 9,354 Residential mortgage-backed securities - Agency (1) — 47 243 10 300 Total available-for-sale investment securities $ 2,661 $ 6,740 $ 243 $ 10 $ 9,654 Held-to-Maturity Investment Securities—Fair Values Residential mortgage-backed securities - Agency (1) $ — $ — $ — $ 269 $ 269 Total held-to-maturity investment securities $ — $ — $ — $ 269 $ 269 (1) Maturities of residential mortgage-backed securities are reflective of the contractual maturities of the investment. At December 31, 2020 One Year After One After Five After Ten Total Available-for-Sale Investment Securities—Weighted-Average Yields (1) U.S Treasury securities 1.91 % 2.25 % — % — % 2.15 % Residential mortgage-backed securities - Agency — % 1.62 % 2.07 % 0.99 % 1.97 % Total available-for-sale investment securities 1.91 % 2.24 % 2.07 % 0.99 % 2.14 % Held-to-Maturity Investment Securities—Weighted-Average Yields Residential mortgage-backed securities — % — % — % 3.13 % 3.13 % Total held-to-maturity investment securities — % — % — % 3.13 % 3.13 % (1) The weighted-average yield for available-for-sale investment securities is calculated based on the amortized cost.

Loan Receivables (Tables)

Loan Receivables (Tables)	12 Months Ended
	Dec. 31, 2020
Receivables [Abstract]
Schedule of Loan Receivables	The Company’s classes of receivables within the two portfolio segments are depicted in the following table (dollars in millions): December 31, 2020 2019 Credit card loans (1)(2) $ 71,472 $ 77,181 Other loans (3) Private student loans (4) 9,954 9,653 Personal loans 7,177 7,687 Other 1,846 1,373 Total other loans 18,977 18,713 Total loan receivables 90,449 95,894 Allowance for credit losses (5) (8,226) (3,383) Net loan receivables $ 82,223 $ 92,511 (1) Amounts include carrying values of $16.7 billion and $18.9 billion underlying investors’ interest in trust debt at December 31, 2020 and 2019, respectively, and $10.6 billion and $12.7 billion in seller’s interest at December 31, 2020 and 2019, respectively. See Note 5: Credit Card and Student Loan Securitization Activities for additional information. (2) Unbilled accrued interest receivable on credit card loans, which is presented as part of other assets in the Company’s consolidated statements of financial condition, was $420 million and $471 million at December 31, 2020 and 2019, respectively. (3) Accrued interest receivable on private student, personal and other loans, which is presented as part of other assets in the Company’s consolidated statements of financial condition, was $469 million, $49 million and $6 million, respectively, at December 31, 2020 and $461 million, $53 million and $4 million, respectively, at December 31, 2019. (4) Amounts include carrying values of $250 million and $292 million in loans pledged as collateral against the note issued from a student loan securitization trust at December 31, 2020 and 2019, respectively. See Note 5: Credit Card and Student Loan Securitization Activities for additional information. (5) Prior to adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach.
Schedule of Credit Risk Profile by FICO Score and Origination Year	The following table provides the distribution of the amortized cost basis (excluding accrued interest receivable presented in other assets) by the most recent FICO scores available for the Company's customers for credit card, private student and personal loan receivables (dollars in millions): Credit Risk Profile by FICO Score December 31, 2020 2019 660 and Above Less than 660 660 and Above Less than 660 $ % $ % $ % $ % Credit card loans (1) $ 58,950 82 % $ 12,522 18 % $ 61,997 80 % $ 15,184 20 % Private student loans by origination year (2)(3) 2020 $ 1,173 95 % $ 60 5 % 2019 1,659 96 % 61 4 % $ 1,176 93 % $ 92 7 % 2018 1,365 96 % 61 4 % 1,518 95 % 79 5 % 2017 1,052 95 % 57 5 % 1,198 95 % 69 5 % 2016 797 94 % 47 6 % 934 94 % 58 6 % Prior 3,422 94 % 200 6 % 4,229 93 % 300 7 % Total private student loans $ 9,468 95 % $ 486 5 % $ 9,055 94 % $ 598 6 % Personal loans by origination year 2020 $ 2,880 99 % $ 25 1 % 2019 2,183 96 % 90 4 % $ 3,529 98 % $ 62 2 % 2018 1,018 92 % 90 8 % 1,941 93 % 140 7 % 2017 558 89 % 69 11 % 1,167 90 % 136 10 % 2016 189 87 % 28 13 % 475 88 % 65 12 % Prior 38 81 % 9 19 % 145 84 % 27 16 % Total personal loans $ 6,866 96 % $ 311 4 % $ 7,257 94 % $ 430 6 % (1) Amounts include $1.0 billion and $956 million of revolving line-of-credit arrangements that were converted to term loans as a result of a TDR program as of December 31, 2020 and 2019, respectively. (2) A majority of student loan originations occur in the third quarter and disbursements can span multiple calendar years. (3) FICO score represents the higher credit score of the cosigner or borrower.
Schedule of Delinquent Loans by Origination Year	The amortized cost basis (excluding accrued interest receivable presented in other assets) of delinquent loans in the Company’s loan portfolio is shown below for credit card, private student and personal loan receivables (dollars in millions): December 31, 2020 2019 30-89 Days 90 or Total Past 30-89 Days 90 or Total Past Credit card loans $ 739 $ 739 $ 1,478 $ 999 $ 1,020 $ 2,019 Private student loans by origination year (1)(2) 2020 $ — $ — $ — 2019 3 1 4 $ — $ — $ — 2018 9 3 12 4 1 5 2017 12 4 16 11 3 14 2016 14 3 17 14 5 19 Prior 72 17 89 106 37 143 Total private student loans $ 110 $ 28 $ 138 $ 135 $ 46 $ 181 Personal loans by origination year 2020 $ 5 $ 2 $ 7 2019 18 9 27 $ 11 $ 3 $ 14 2018 15 7 22 27 11 38 2017 10 5 15 22 10 32 2016 4 1 5 10 5 15 Prior 1 1 2 4 2 6 Total personal loans $ 53 $ 25 $ 78 $ 74 $ 31 $ 105 (1) Student loans may include a deferment period, during which customers are not required to make payments while enrolled in school at least half time as determined by the school. During a deferment period, these loans do not advance into delinquency. (2) Includes PCD loans for all periods presented.
Schedule of Changes in the Allowance for Credit Losses	The following tables provide changes in the Company’s allowance for credit losses (dollars in millions): For the Year Ended December 31, 2020 Credit Card Loans Private Student Personal Loans Other Loans Total Balance at December 31, 2019 (1) $ 2,883 $ 148 $ 348 $ 4 $ 3,383 Cumulative effect of ASU No. 2016-13 adoption (2) 1,667 505 265 24 2,461 Balance at January 1, 2020 4,550 653 613 28 5,844 Additions Provision for credit losses (3) 4,379 251 476 11 5,117 Deductions Charge-offs (3,101) (85) (289) (1) (3,476) Recoveries 663 21 57 — 741 Net charge-offs (2,438) (64) (232) (1) (2,735) Balance at December 31, 2020 $ 6,491 $ 840 $ 857 $ 38 $ 8,226 For the Year Ended December 31, 2019 Credit Card Loans Private Student Personal Loans Other Loans Total Balance at December 31, 2018 (1) $ 2,528 $ 169 $ 338 $ 6 $ 3,041 Additions Provision for credit losses (1) 2,849 51 332 (1) 3,231 Deductions Charge-offs (3,165) (82) (369) (1) (3,617) Recoveries 671 13 47 — 731 Net charge-offs (4) (2,494) (69) (322) (1) (2,886) Other (5) — (3) — — (3) Balance at December 31, 2019 (1) $ 2,883 $ 148 $ 348 $ 4 $ 3,383 For the Year Ended December 31, 2018 Credit Card Loans Private Student Personal Loans Other Loans Total Balance at December 31, 2017 (1) $ 2,147 $ 162 $ 301 $ 11 $ 2,621 Additions Provision for credit losses (1) 2,594 95 345 1 3,035 Deductions Charge-offs (2,734) (97) (345) (6) (3,182) Recoveries 521 12 37 — 570 Net charge-offs (4) (2,213) (85) (308) (6) (2,612) Other (5) — (3) — — (3) Balance at December 31, 2018 (1) $ 2,528 $ 169 $ 338 $ 6 $ 3,041 (1) Prior to the adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach. (2) Represents the adjustment to the allowance for credit losses as a result of the adoption of ASU No. 2016-13 on January 1, 2020. (3) Excludes a $17 million build of the liability for expected credit losses on unfunded commitments for the year ended December 31, 2020, as the liability is recorded in accrued expenses and other liabilities in the Company’s consolidated statements of financial condition. (4) Prior to the 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. (5) 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).
Schedule of Net Charge-offs of Interest and Fee Revenues on Loan Receivables	Net charge-offs of principal are recorded against the allowance for credit losses, as shown in the preceding table. Information regarding net charge-offs of interest and fee revenues on credit card and other loans is as follows (dollars in millions): For the Years Ended December 31, 2020 2019 2018 Interest and fees accrued subsequently charged off, net of recoveries (recorded as a reduction of interest income) $ 484 $ 515 $ 442 Fees accrued subsequently charged off, net of recoveries (recorded as a reduction to other income) $ 117 $ 123 $ 109
Schedule of Delinquent and Non-Accruing Loans	The amortized cost basis (excluding accrued interest receivable presented in other assets) of delinquent and non-accruing loans in the Company’s loan portfolio is shown below for each class of loan receivables (dollars in millions): 30-89 Days 90 or Total Past 90 or Total Non-accruing (1) At December 31, 2020 Credit card loans $ 739 $ 739 $ 1,478 $ 687 $ 209 Other loans Private student loans (2) 110 28 138 27 12 Personal loans 53 25 78 23 12 Other 8 3 11 — 10 Total other loans 171 56 227 50 34 Total loan receivables $ 910 $ 795 $ 1,705 $ 737 $ 243 At December 31, 2019 Credit card loans $ 999 $ 1,020 $ 2,019 $ 940 $ 237 Other loans Private student loans (2) 135 46 181 45 11 Personal loans 74 31 105 29 12 Other 5 2 7 — 6 Total other loans 214 79 293 74 29 Total loan receivables $ 1,213 $ 1,099 $ 2,312 $ 1,014 $ 266 (1) The Company estimates that the gross interest income that would have been recorded in accordance with the original terms of non-accruing credit card loans was $33 million, $45 million and $41 million for the years ended December 31, 2020, 2019 and 2018, respectively. The Company does not separately track the amount of gross interest income that would have been recorded in accordance with the original terms of loans. This amount was estimated based on customers’ current balances and most recent interest rates. (2) Includes PCD loans for all periods presented.
Schedule of Loans That Entered a Modification Program During the Period	The following table provides information on loans that entered a TDR program during the period (dollars in millions): For the Years Ended December 31, 2020 2019 2018 Number of Accounts Balances Number of Accounts Balances Number of Accounts Balances Accounts that entered a TDR program during the period Credit card loans (1) 152,055 $ 1,022 368,009 $ 2,364 268,817 $ 1,713 Private student loans 1,916 $ 35 6,742 $ 124 4,057 $ 74 Personal loans 8,805 $ 114 10,945 $ 147 8,260 $ 111 (1) Accounts that entered a credit card TDR program include $670 million, $741 million and $491 million that were converted from revolving line-of-credit arrangements to term loans during the years ended December 31, 2020, 2019 and 2018, respectively.
Schedule of Troubled Debt Restructurings That Subsequently Defaulted	The following table presents the carrying value of loans that experienced a payment default during the period that had been modified in a TDR during the 15 months preceding the end of each period (dollars in millions): For the Years Ended December 31, 2020 2019 2018 Number of Accounts Aggregated Outstanding Balances Upon Default Number of Accounts Aggregated Outstanding Balances Upon Default Number of Accounts Aggregated Outstanding Balances Upon Default Troubled debt restructurings that subsequently defaulted Credit card loans (1)(2) 48,075 $ 276 71,326 $ 410 42,659 $ 239 Private student loans (3) 1,119 $ 22 1,406 $ 27 1,041 $ 19 Personal loans (2) 3,145 $ 46 4,152 $ 59 2,955 $ 40 (1) Terms revert back to the pre-modification terms for customers who default from a temporary program and charging privileges remain suspended in most cases. (2) For credit card loans and personal loans, a customer defaults from a modification program either after two consecutive missed payments or at charge-off, depending on the program. The outstanding balance upon default is generally the loan balance at the end of the month prior to default.
Schedule of Geographic Distribution of Loan Receivables	The Company originates credit card loans throughout the United States. The geographic distribution of the Company’s credit card loan receivables was as follows (dollars in millions): December 31, 2020 2019 $ % $ % California $ 6,273 8.8 % $ 7,110 9.2 % Texas 6,182 8.6 6,543 8.5 Florida 4,931 6.9 5,176 6.7 New York 4,836 6.8 5,335 6.9 Illinois 3,714 5.2 4,084 5.3 Pennsylvania 3,616 5.1 3,873 5.0 Ohio 3,005 4.2 3,207 4.2 New Jersey 2,558 3.6 2,807 3.6 Georgia 2,204 3.1 2,325 3.0 Michigan 1,983 2.8 2,165 2.8 Other 32,170 44.9 34,556 44.8 Total credit card loans $ 71,472 100 % $ 77,181 100 % The Company originates private student, personal and other loans throughout the United States. The geographic distribution of private student, personal and other loan receivables was as follows (dollars in millions): December 31, 2020 2019 $ % $ % New York $ 1,797 9.5 % $ 1,859 9.9 % California 1,706 9.0 1,764 9.4 Pennsylvania 1,317 6.9 1,275 6.8 Texas 1,224 6.4 1,151 6.2 Illinois 1,163 6.1 1,157 6.2 New Jersey 1,002 5.3 980 5.2 Florida 975 5.1 930 5.0 Ohio 758 4.0 739 4.0 Massachusetts 588 3.1 594 3.2 Michigan 585 3.1 585 3.1 Other 7,862 41.5 7,679 41.0 Total other loans $ 18,977 100 % $ 18,713 100 %

Credit Card and Student Loan _2

Credit Card and Student Loan Securitization Activities (Tables)	12 Months Ended
	Dec. 31, 2020
Variable Interest Entities Disclosure [Abstract]
Schedule of Restricted Credit Card Securitized Assets	The carrying values of these restricted assets, which are presented on the Company’s consolidated statements of financial condition as relating to securitization activities, are shown in the following table (dollars in millions): December 31, 2020 2019 Restricted cash $ 16 $ 28 Investors’ interests held by third-party investors 10,600 14,100 Investors’ interests held by wholly-owned subsidiaries of Discover Bank 6,121 4,796 Seller’s interest 10,575 12,652 Loan receivables (1) 27,296 31,548 Allowance for credit losses allocated to securitized loan receivables (1)(2) (1,936) (1,179) Net loan receivables 25,360 30,369 Other 3 5 Carrying value of assets of consolidated variable interest entities $ 25,379 $ 30,402 (1) The Company maintains its allowance for credit losses at an amount equal to lifetime expected credit losses associated with all loan receivables, which includes all loan receivables in the trusts. Therefore, credit risk associated with the transferred receivables is fully reflected on the Company’s balance sheet in accordance with GAAP. (2) Prior to the adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach.
Schedule of Restricted Student Loan Securitized Assets	The carrying values of these restricted assets, which are presented on the Company’s consolidated statements of financial condition as relating to securitization activities, are shown in the following table (dollars in millions): December 31, 2020 2019 Restricted cash $ 9 $ 12 Student loan receivables 250 292 Carrying value of assets of consolidated variable interest entities $ 259 $ 304

Premises and Equipment (Tables)

Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Schedule of Premises and Equipment	A summary of premises and equipment, net is as follows (dollars in millions): December 31, 2020 2019 Land $ 38 $ 42 Buildings and improvements 673 693 Furniture, fixtures and equipment 1,125 1,082 Software 901 851 Premises and equipment 2,737 2,668 Less: accumulated depreciation (1,349) (1,276) Less: accumulated amortization of software (361) (335) Premises and equipment, net $ 1,027 $ 1,057

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets	The following table summarizes the Company’s intangible assets (dollars in millions): December 31, 2020 2019 Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net Amortizable intangible assets Customer relationships $ 69 $ 69 $ — $ 69 $ 68 $ 1 Trade name and other 8 5 3 8 5 3 Total amortizable intangible assets 77 74 3 77 73 4 Non-amortizable intangible assets Trade names 92 — 92 128 — 128 International transaction processing rights — — — 23 — 23 Total non-amortizable intangible assets 92 — 92 151 — 151 Total intangible assets $ 169 $ 74 $ 95 $ 228 $ 73 $ 155

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2020
Deposits [Abstract]
Schedule of Interest Bearing Deposit Accounts	The following table provides a summary of interest-bearing deposit accounts (dollars in millions): December 31, 2020 2019 Certificates of deposit in amounts less than $100,000 $ 19,105 $ 25,113 Certificates of deposit in amounts $100,000 or greater (1) 9,164 9,268 Savings deposits, including money market deposit accounts 47,426 37,574 Total interest-bearing deposits $ 75,695 $ 71,955 (1) Includes $2.6 billion in certificates of deposit equal to or greater than $250,000, the Federal Deposit Insurance Corporation (“FDIC”) insurance limit, as of December 31, 2020 and 2019.
Schedule of $100,000 or More Certificates of Deposit Maturities	The following table summarizes certificates of deposit in amounts of $100,000 or greater by contractual maturity (dollars in millions): December 31, 2020 Three months or less $ 2,461 Over three months through six months 1,669 Over six months through twelve months 2,883 Over twelve months 2,151 Total $ 9,164
Schedule of Certificates of Deposit Maturities	The following table summarizes certificates of deposit maturing over each of the next five years and thereafter (dollars in millions): December 31, 2020 2021 $ 17,850 2022 4,520 2023 2,259 2024 1,363 2025 866 Thereafter 1,411 Total $ 28,269

Long-Term Borrowings (Tables)

Long-Term Borrowings (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Schedule of Long-Term Borrowings and Weighted Average Interest Rates	Long-term borrowings consist of borrowings having original maturities of one year or more. The following table provides a summary of the Company’s long-term borrowings and weighted-average interest rates on outstanding balances (dollars in millions): December 31, 2020 December 31, 2019 Maturity Interest Weighted-Average Interest Rate Outstanding Amount Outstanding Amount Securitized Debt Fixed-rate asset-backed securities (1) 2021-2024 1.85% - 3.32% 2.74% $ 6,041 $ 8,609 Floating-rate asset-backed securities (2)(3) 2021-2024 0.39% - 0.76% 0.56% 4,669 5,515 Total Discover Card Master Trust I and Discover Card Execution Note Trust 10,710 14,124 Floating-rate asset-backed security (4)(5) 2031 4.25% 4.25% 130 160 Total student loan securitization trust 130 160 Total long-term borrowings - owed to securitization investors 10,840 14,284 Discover Financial Services (Parent Company) Fixed-rate senior notes 2022-2027 3.75% - 5.20% 4.16% 3,337 3,296 Fixed-rate retail notes 2021-2031 2.85% - 4.60% 3.73% 336 340 Discover Bank Fixed-rate senior bank notes (1) 2021-2030 2.45% - 4.65% 3.57% 6,213 6,785 Fixed-rate subordinated bank notes (1) 2028 4.68% 4.68% 515 996 Total long-term borrowings $ 21,241 $ 25,701 (1) The Company uses interest rate swaps to hedge portions of these long-term borrowings against changes in fair value attributable to changes in London Interbank Offered Rate (“LIBOR”) or Overnight Index Swap (“OIS”) Rate. Use of these interest rate swaps impacts carrying value of the debt. See Note 21: Derivatives and Hedging Activities. (2) Discover Card Execution Note Trust floating-rate asset-backed securities include issuances with the following interest rate terms: 1-month LIBOR + 23 to 60 basis points as of December 31, 2020. (3) The Company uses interest rate swaps to manage its exposure to changes in interest rates related to future cash flows resulting from interest payments on a portion of these long-term borrowings. There is no impact on debt carrying value from use of these interest rate swaps. See Note 21: Derivatives and Hedging Activities. (4) The student loan securitization trust floating-rate asset-backed security includes an issuance with the following interest rate term: Prime rate + 100 basis points as of December 31, 2020. (5) Repayment of this debt is dependent upon the timing of principal and interest payments on the underlying student loans. The date shown represents final maturity date.
Schedule of Long-Term Borrowings Maturities	The following table summarizes long-term borrowings maturing over each of the next five years and thereafter (dollars in millions): Amount 2021 $ 4,217 2022 5,201 2023 3,402 2024 2,625 2025 533 Thereafter 5,263 Total $ 21,241

Stock-Based Compensation Plans

Stock-Based Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Stock-Based Compensation Plans Compensation Cost, Net of Forfeitures	The following table details the compensation cost, net of forfeitures (dollars in millions): For the Years Ended December 31, 2020 2019 2018 RSUs $ 49 $ 49 $ 49 PSUs (1) (8) 20 32 Total stock-based compensation expense $ 41 $ 69 $ 81 Income tax benefit $ 9 $ 12 $ 15 (1) Total PSU expense for the year ended December 31, 2020, includes an incremental $2.4 million representing a modification to the 2018 PSU award. The nature of the modification was to adjust the payout to compensate for the 2020 CECL adoption impact on EPS.
Schedule of Restricted Stock Unit Activity	The following table sets forth the activity related to vested and unvested RSUs: Number of Units Weighted-Average Remaining Contractual Term (in years) Aggregate RSUs at December 31, 2019 2,148,976 $ 182 Granted 631,692 Conversions to common stock (769,525) Forfeited (76,744) RSUs at December 31, 2020 1,934,399 0.83 $ 175 Vested and convertible RSUs at December 31, 2020 728,787 0.00 $ 66 The following table sets forth the activity related to unvested RSUs: Number of Units Weighted-Average Grant-Date Fair Value Unvested RSUs at December 31, 2019 1) 1,104,562 $ 72.33 Granted 631,692 $ 76.58 Vested (705,427) $ 72.56 Forfeited (76,744) $ 77.19 Unvested RSUs at December 31, 2020 (1) 954,083 $ 74.58 (1) Unvested RSUs represent awards where recipients have yet to satisfy either explicit vesting terms or retirement-eligibility requirements.
Schedule of Intrinsic Value of RSUs Converted to Common Stock and Grant Date Fair Value of RSUs Vested	The following table summarizes the total intrinsic value of the RSUs converted to common stock and the total grant-date fair value of RSUs vested (dollars in millions, except weighted-average grant-date fair value amounts): For the Years Ended December 31, 2020 2019 2018 Intrinsic value of RSUs converted to common stock $ 55 $ 93 $ 67 Grant-date fair value of RSUs vested $ 51 $ 48 $ 54 Weighted-average grant-date fair value of RSUs granted $ 76.58 $ 73.52 $ 77.53
Schedule of Peformance Stock Unit Activity	The following table sets forth the activity related to vested and unvested PSUs: Number of Units Weighted-Average Grant-Date Fair Value Weighted-Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in millions) PSUs at December 31, 2019 (1) 723,533 $ 73.56 $ 61 Granted 299,936 $ 85.25 Conversions to common stock (243,100) $ 71.17 Forfeited (51,641) $ 75.81 PSUs at December 31, 2020 (1)(2)(3)(4) 728,728 $ 79.01 1.18 $ 66 (1) All PSUs outstanding at December 31, 2020 and December 31, 2019, are unvested PSUs. (2) Includes 225,182 PSUs granted in 2018 that are earned based on the Company’s achievement of earnings per share (“EPS”) during the three-year performance period which ends December 31, 2020, and are subject to the requisite service period which ended February 1, 2021. (3) Includes 211,799 PSUs granted in 2019 that are earned based on the Company’s achievement of EPS during the three-year performance period which ends December 31, 2021, and are subject to the requisite service period which ends February 1, 2022. (4) Includes 291,747 PSUs granted in 2020 that may be earned based on the Company’s achievement of EPS during the three-year performance period which ends December 31, 2022, and are subject to the requisite service period which ends February 1, 2023.
Schedule of Intrinsic Value of PSUs Converted to Common Stock and Grant Date Fair Value of PSUs Vested	The following table summarizes the total intrinsic value of the PSUs converted to common stock and the total grant-date fair value of PSUs vested (dollars in millions, except weighted-average grant-date fair value amounts): For the Years Ended December 31, 2020 2019 2018 Intrinsic value of PSUs converted to common stock $ 21 $ 33 $ 30 Grant-date fair value of PSUs vested $ 17 $ 21 $ 17 Weighted-average grant-date fair value of PSUs granted $ 85.25 $ 71.62 $ 77.75

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Schedule of Net Periodic Benefit Cost	Net periodic benefit cost expensed by the Company included the following components (dollars in millions): For the Years Ended December 31, 2020 2019 2018 Interest cost on projected benefit obligation $ 21 $ 23 $ 22 Expected return on plan assets (25) (29) (26) Net amortization 7 4 5 Net periodic benefit cost (income) $ 3 $ (2) $ 1
Schedule of Pretax Amounts Recognized in AOCI Not Recognized as Components of Net Periodic Benefit Cost	Pretax amounts recognized in AOCI that have not yet been recognized as components of net periodic benefit cost consist of (dollars in millions): December 31, 2020 Net loss $ (299) Total $ (299)
Schedule of Funded Status and Changes in Benefit Obligations and Fair Value of Plan Assets	The following table provides a reconciliation of the changes in the benefit obligation and fair value of plan assets as well as a summary of the Discover Pension Plan’s funded status (dollars in millions): For the Years Ended December 31, 2020 2019 Reconciliation of benefit obligation Benefit obligation at beginning of year $ 650 $ 550 Interest cost 21 23 Actuarial losses 98 98 Benefits paid (21) (21) Benefit obligation at end of year 748 650 Reconciliation of fair value of plan assets Fair value of plan assets at beginning of year 525 455 Actual return on plan assets 110 91 Benefits paid (21) (21) Fair value of plan assets at end of year 614 525 Unfunded status (recorded in accrued expenses and other liabilities) $ (134) $ (125)
Schedule of Assumptions Used to Determine Benefit Obligations and Net Periodic Benefit Cost	The following table presents the assumptions used to determine the benefit obligation: December 31, 2020 2019 Discount rate 2.47 % 3.30 % The following table presents the assumptions used to determine net periodic benefit cost: For the Years Ended December 31, 2020 2019 2018 Discount rate 3.30 % 4.27 % 3.68 % Expected long-term rate of return on plan assets 5.08 % 6.15 % 6.15 %
Schedule of Pension Plan Assets by Level Within the Fair Value Hierarchy	The table below presents information about the Discover Pension Plan assets and indicates the level within the fair value hierarchy, as defined by ASC Topic 820, with which each item is associated as of the end of the current period. For a description of the fair value hierarchy, see Note 20: Fair Value Measurements (dollars in millions): Level 1 Level 2 Level 3 Net Asset Value Total Net Asset Allocation Balance at December 31, 2020 Assets Cash $ 15 $ — $ — $ — $ 15 3 % Domestic small/mid cap equity fund — 8 — — 8 1 % Emerging markets equity fund — — — 20 20 3 % Global equity fund — 83 4 49 136 22 % Domestic large cap equity fund — 10 — — 10 2 % Long duration credit fund — 243 — — 243 40 % Non-core fixed income fund — — 72 — 72 12 % United States Treasury securities 81 — — — 81 13 % Temporary investment fund — 31 — — 31 5 % Total assets 96 375 76 69 616 Liabilities Futures contracts — 2 — — 2 1 % Total liabilities — 2 — — 2 Net assets $ 96 $ 373 $ 76 $ 69 $ 614 100 % Balance at December 31, 2019 Assets Cash $ 7 $ — $ — $ — $ 7 1 % Domestic small/mid cap equity fund — 6 — — 6 1 % Emerging markets equity fund — — — 16 16 3 % Global equity fund — 73 3 45 121 23 % Domestic large cap equity fund — 8 — — 8 2 % Long duration credit fund — 205 — — 205 39 % Non-core fixed income fund — — 64 — 64 12 % United States Treasury securities 87 — — — 87 17 % Temporary investment fund — 15 — — 15 3 % Total assets 94 307 67 61 529 Liabilities Futures contracts — 4 — — 4 1 % Total liabilities — 4 — — 4 Net assets $ 94 $ 303 $ 67 $ 61 $ 525 100 %
Schedule of Expected Benefit Payments for Next Five Years and Thereafter	Expected benefit payments associated with the Discover Pension Plan for each of the next five years and in aggregate for the years thereafter are as follows (dollars in millions): December 31, 2020 2021 $ 18 2022 $ 19 2023 $ 20 2024 $ 22 2025 $ 23 Following five years thereafter $ 140

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2020
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Changes in Accumulated Other Comprehensive Income (Loss)	Changes in each component of AOCI were as follows (dollars in millions): Unrealized Gains (Losses) on Available-for-Sale Investment Securities, Net of Tax (Losses) Gains on Cash Flow Hedges, Net of Tax Losses on Pension Plan, Net of Tax AOCI For the Year Ended December 31, 2020 Balance at December 31, 2019 $ 112 $ (17) $ (214) $ (119) Net change 172 5 (13) 164 Balance at December 31, 2020 $ 284 $ (12) $ (227) $ 45 For the Year Ended December 31, 2019 Balance at December 31, 2018 $ 10 $ 22 $ (188) $ (156) Net change 102 (39) (26) 37 Balance at December 31, 2019 $ 112 $ (17) $ (214) $ (119) For the Year Ended December 31, 2018 Balance at December 31, 2017 $ (5) $ 10 $ (157) $ (152) Cumulative effect of ASU No. 2018-02 adoption (1) (1) 3 (31) (29) Net change 16 9 — 25 Balance at December 31, 2018 $ 10 $ 22 $ (188) $ (156) (1) Represents the adjustment to AOCI as a result of adoption of ASU No. 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income, in the second quarter of 2018.
Schedule of Other Comprehensive Income Before Reclassifications and Amounts Reclassified from AOCI	The following table presents each component of OCI before reclassifications and amounts reclassified from AOCI for each component of OCI before- and after-tax (dollars in millions): Before Tax Tax (Expense) Benefit Net of Tax For the Year Ended December 31, 2020 Available-for-Sale Investment Securities Net unrealized holding gains arising during the period $ 227 $ (55) $ 172 Net change $ 227 $ (55) $ 172 Cash Flow Hedges Net unrealized losses arising during the period $ (7) $ 3 $ (4) Amounts reclassified from AOCI 12 (3) 9 Net change $ 5 $ — $ 5 Pension Plan Unrealized losses arising during the period $ (17) $ 4 $ (13) Net change $ (17) $ 4 $ (13) For the Year Ended December 31, 2019 Available-for-Sale Investment Securities Net unrealized holding gains arising during the period $ 135 $ (33) $ 102 Net change $ 135 $ (33) $ 102 Cash Flow Hedges Net unrealized losses arising during the period $ (42) $ 7 $ (35) Amounts reclassified from AOCI (5) 1 (4) Net change $ (47) $ 8 $ (39) Pension Plan Unrealized losses arising during the period $ (34) $ 8 $ (26) Net change $ (34) $ 8 $ (26) For the Year Ended December 31, 2018 Available-for-Sale Investment Securities Net unrealized holding gains arising during the period $ 23 $ (7) $ 16 Net change $ 23 $ (7) $ 16 Cash Flow Hedges Net unrealized gains arising during the period $ 17 $ (4) $ 13 Amounts reclassified from AOCI (6) 2 (4) Net change $ 11 $ (2) $ 9

Other Expense (Tables)

Other Expense (Tables)	12 Months Ended
	Dec. 31, 2020
Other Income and Expenses [Abstract]
Schedule of Other Expense	Total other expense includes the following components (dollars in millions): For the Years Ended December 31, 2020 2019 2018 Postage $ 93 $ 93 $ 86 Fraud losses and other charges 96 96 83 Supplies 51 34 29 Incentive expense 57 84 85 Impairment charges 59 — — Other expense 240 196 186 Total other expense $ 596 $ 503 $ 469

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Schedule of Income Tax Expense	Income tax expense consisted of the following (dollars in millions): For the Years Ended December 31, 2020 2019 2018 Current United States federal $ 807 $ 836 $ 839 United States state and local 159 175 206 Total 966 1,011 1,045 Deferred United States federal (585) (116) (163) United States state and local (87) (17) (27) Total (672) (133) (190) Income tax expense $ 294 $ 878 $ 855
Schedule of Reconciliation the Effective Tax Rate to the U.S. Federal Statutory Income Tax Rate	The following table reconciles the Company’s effective tax rate to the United States federal statutory income tax rate: For the Years Ended December 31, 2020 2019 2018 United States federal statutory income tax rate 21.0 % 21.0 % 21.0 % United States state, local and other income taxes, net of United States federal income tax benefits 3.4 3.5 3.6 Tax credits (4.4) (1.4) (1.3) Other 0.5 (0.2) 0.5 Effective income tax rate 20.5 % 22.9 % 23.8 %
Schedule of Deferred Tax Assets and Liabilities	Significant components of the Company’s net deferred income taxes, which are included in other assets in the Company’s consolidated statements of financial condition, were as follows (dollars in millions): December 31, 2020 2019 Deferred tax assets Allowance for credit losses $ 1,997 $ 819 Compensation and benefits 84 65 Other 73 50 Total deferred tax assets before valuation allowance 2,154 934 Valuation allowance (1) (1) Total deferred tax assets, net of valuation allowance 2,153 933 Deferred tax liabilities Depreciation and software amortization (172) (167) Unrealized gains (90) (33) Customer fees and rewards (37) (81) Deferred loan origination costs (21) (28) Debt exchange premium (17) (26) Intangibles (15) (28) Other (26) (19) Total deferred tax liabilities (378) (382) Net deferred tax assets $ 1,775 $ 551
Schedule of Reconciliation of Beginning and Ending Unrecognized Tax Benefits	A reconciliation of beginning and ending unrecognized tax benefits is as follows (dollars in millions): For the Years Ended December 31, 2020 2019 2018 Balance at beginning of period $ 61 $ 83 $ 123 Additions Current year tax positions 5 4 5 Prior year tax positions 3 — 6 Reductions Prior year tax positions — (22) (17) Settlements with taxing authorities (2) — (25) Expired statute of limitations (11) (4) (9) Balance at end of period (1) $ 56 $ 61 $ 83 (1) For the years ended December 31, 2020, 2019 and 2018, amounts included $51 million, $54 million and $74 million, respectively, of unrecognized tax benefits, which, if recognized, would favorably affect the effective tax rate.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Schedule of Basic and Diluted EPS	The following table presents the calculation of basic and diluted earnings per share (dollars in millions, except per share amounts): For the Years Ended December 31, 2020 2019 2018 Numerator Net income $ 1,141 $ 2,957 $ 2,742 Preferred stock dividends (31) (31) (31) Net income available to common stockholders 1,110 2,926 2,711 Income allocated to participating securities (6) (18) (22) Net income allocated to common stockholders $ 1,104 $ 2,908 $ 2,689 Denominator Weighted-average shares of common stock outstanding 307 320 344 Effect of dilutive common stock equivalents — — 1 Weighted-average shares of common stock outstanding and common stock equivalents 307 320 345 Basic earnings per common share $ 3.60 $ 9.09 $ 7.81 Diluted earnings per common share $ 3.60 $ 9.08 $ 7.79

Capital Adequacy (Tables)

Capital Adequacy (Tables)	12 Months Ended
	Dec. 31, 2020
Broker-Dealer, Net Capital Requirement, SEC Regulation [Abstract]
Schedule of Minimum and Well-Capitalized Requirements	The following table shows the actual capital amounts and ratios of the Company and Discover Bank and comparisons of each to the regulatory minimum and “well-capitalized” requirements (dollars in millions): Actual Minimum Capital Capital Requirements Amount Ratio (1) Amount Ratio Amount (2) Ratio (2) December 31, 2020 Total capital (to risk-weighted assets) Discover Financial Services $ 14,711 16.1 % $ 7,298 ≥8.0% $ 9,123 ≥10.0% Discover Bank $ 14,507 16.1 % $ 7,214 ≥8.0% $ 9,018 ≥10.0% Tier 1 capital (to risk-weighted assets) Discover Financial Services $ 13,006 14.3 % $ 5,474 ≥6.0% $ 5,474 ≥6.0% Discover Bank $ 12,415 13.8 % $ 5,411 ≥6.0% $ 7,214 ≥8.0% Tier 1 capital (to average assets) Discover Financial Services $ 13,006 10.9 % $ 4,757 ≥4.0% N/A N/A Discover Bank $ 12,415 10.5 % $ 4,709 ≥4.0% $ 5,886 ≥5.0% Common Equity Tier 1 (to risk-weighted assets) Discover Financial Services $ 11,950 13.1 % $ 4,105 ≥4.5% N/A N/A Discover Bank $ 12,415 13.8 % $ 4,058 ≥4.5% $ 5,862 ≥6.5% December 31, 2019 Total capital (to risk-weighted assets) Discover Financial Services $ 13,250 13.5 % $ 7,860 ≥8.0% $ 9,825 ≥10.0% Discover Bank $ 13,441 13.8 % $ 7,776 ≥8.0% $ 9,720 ≥10.0% Tier 1 capital (to risk-weighted assets) Discover Financial Services $ 11,595 11.8 % $ 5,895 ≥6.0% $ 5,895 ≥6.0% Discover Bank $ 11,203 11.5 % $ 5,832 ≥6.0% $ 7,776 ≥8.0% Tier 1 capital (to average assets) Discover Financial Services $ 11,595 10.3 % $ 4,482 ≥4.0% N/A N/A Discover Bank $ 11,203 10.1 % $ 4,435 ≥4.0% $ 5,544 ≥5.0% Common Equity Tier 1 (to risk-weighted assets) Discover Financial Services $ 11,032 11.2 % $ 4,421 ≥4.5% N/A N/A Discover Bank $ 11,203 11.5 % $ 4,374 ≥4.5% $ 6,318 ≥6.5% (1) Capital ratios are calculated based on the Basel III Standardized Approach rules, subject to applicable transition provisions, including CECL transition provisions. (2) The Basel III rules do not establish well-capitalized thresholds for these measures for bank holding companies. Existing well-capitalized thresholds established in the Federal Reserve’s Regulation Y have been included where available.

Commitments, Contingencies an_2

Commitments, Contingencies and Guarantees (Tables)	12 Months Ended
	Dec. 31, 2020
Merchant Chargeback Guarantees [Member]
Guarantor Obligations [Line Items]
Schedule of Maximum Potential Counterparty Exposures Related to Settlement Guarantees and Merchant Chargeback Guarantee	The following table summarizes certain information regarding merchant chargeback guarantees (dollars in millions): For the Years Ended December 31, 2020 2019 2018 Aggregate sales transaction volume (1) $ 175,026 $ 172,463 $ 158,910 (1) Represents transactions processed on the Discover Network for which a potential liability exists that, in aggregate, can differ from credit card sales volume.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis	Assets and liabilities measured at fair value on a recurring basis are as follows (dollars in millions): Quoted Price in Active Markets Significant Other Observable Inputs Significant Unobservable Inputs Total Balance at December 31, 2020 Assets Fair value - OCI United States Treasury securities $ 9,354 $ — $ — $ 9,354 Residential mortgage-backed securities - Agency — 300 — 300 Available-for-sale investment securities $ 9,354 $ 300 $ — $ 9,654 Fair value - Net income Derivative financial instruments - fair value hedges (1) $ — $ 1 $ — $ 1 Balance at December 31, 2019 Assets Fair value - OCI United States Treasury securities $ 9,906 $ — $ — $ 9,906 Residential mortgage-backed securities - Agency — 417 — 417 Available-for-sale investment securities $ 9,906 $ 417 $ — $ 10,323 Liabilities Fair value - OCI Derivative financial instruments - cash flow hedges (1) $ — $ 2 $ — $ 2 Fair value - Net income Derivative financial instruments - fair value hedges (1) $ — $ 4 $ — $ 4 Derivative financial instruments - foreign exchange forward contracts (1) $ — $ 1 $ — $ 1 (1) Derivative instrument carrying values in an asset or liability position are presented as part of other assets or accrued expenses and other liabilities, respectively, in the Company’s consolidated statements of financial condition.
Schedule of Financial Instruments Measured at Other Than Fair Value	The following tables disclose the estimated fair value of the Company’s financial assets and financial liabilities that are not required to be carried at fair value (dollars in millions): Balance at December 31, 2020 Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Carrying Value Assets Amortized cost Residential mortgage-backed securities - Agency $ — $ 269 $ — $ 269 $ 260 Held-to-maturity investment securities $ — $ 269 $ — $ 269 $ 260 Net loan receivables $ — $ — $ 91,200 $ 91,200 $ 82,223 Carrying value approximates fair value (1) Cash and cash equivalents $ 13,564 $ — $ — $ 13,564 $ 13,564 Restricted cash $ 25 $ — $ — $ 25 $ 25 Other short-term investments $ 2,200 $ — $ — $ 2,200 $ 2,200 Accrued interest receivables (2) $ — $ 992 $ — $ 992 $ 992 Liabilities Amortized cost Time deposits (3) $ — $ 29,090 $ — $ 29,090 $ 28,269 Long-term borrowings - owed to securitization investors $ — $ 10,794 $ 130 $ 10,924 $ 10,840 Other long-term borrowings — 11,418 — 11,418 10,401 Long-term borrowings $ — $ 22,212 $ 130 $ 22,342 $ 21,241 Carrying value approximates fair value (1) Accrued interest payables (2) $ — $ 233 $ — $ 233 $ 233 (1) The carrying values of these assets and liabilities approximate fair value due to their short-term nature. (2) Accrued interest receivable and payable carrying values are presented as part of other assets or accrued expenses and other liabilities, respectively, in the Company’s consolidated statements of financial condition. (3) Excludes deposits without contractually defined maturities for all periods presented. Balance at December 31, 2019 Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Carrying Value Assets Amortized cost Residential mortgage-backed securities - Agency $ — $ 274 $ — $ 274 $ 272 Held-to-maturity investment securities $ — $ 274 $ — $ 274 $ 272 Net loan receivables $ — $ — $ 96,094 $ 96,094 $ 92,511 Carrying value approximates fair value (1) Cash and cash equivalents $ 6,924 $ — $ — $ 6,924 $ 6,924 Restricted cash $ 40 $ — $ — $ 40 $ 40 Accrued interest receivables (2) $ — $ 1,044 $ — $ 1,044 $ 1,044 Liabilities Amortized cost Time deposits (3) $ — $ 34,910 $ — $ 34,910 $ 34,381 Long-term borrowings - owed to securitization investors $ — $ 14,211 $ 172 $ 14,383 $ 14,284 Other long-term borrowings — 12,189 — 12,189 11,417 Long-term borrowings $ — $ 26,400 $ 172 $ 26,572 $ 25,701 Carrying value approximates fair value (1) Accrued interest payables (2) $ — $ 283 $ — $ 283 $ 283 (1) The carrying values of these assets and liabilities approximate fair value due to their short-term nature. (2) Accrued interest receivable and payable carrying values are presented as part of other assets or accrued expenses and other liabilities, respectively, in the Company’s consolidated statements of financial condition. (3) Excludes deposits without contractually defined maturities for all periods presented.

Derivatives and Hedging Activ_2

Derivatives and Hedging Activities (Tables)	12 Months Ended
	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Fair Value and Outstanding Notional Amounts of Derivative Instruments and Related Collateral Balances	The following table summarizes the fair value (including accrued interest) and outstanding notional amounts of derivative instruments and related collateral balances (dollars in millions): December 31, 2020 December 31, 2019 Notional Number of Derivative Assets Derivative Liabilities Notional Derivative Assets Derivative Liabilities Derivatives designated as hedges Interest rate swaps—cash flow hedge $ 250 1 $ — $ — $ 900 $ — $ 2 Interest rate swaps—fair value hedge $ 11,625 15 1 — $ 14,275 — 4 Derivatives not designated as hedges Foreign exchange forward contracts (1) $ 24 6 — — $ 38 — 1 Total gross derivative assets/liabilities (2) 1 — — 7 Less: collateral held/posted (3) — — — (7) Total net derivative assets/liabilities $ 1 $ — $ — $ — (1) The foreign exchange forward contracts have notional amounts of EUR 6 million, GBP 6 million, SGD 1 million and INR 596 million as of December 31, 2020, and notional amounts of EUR 9 million, GBP 14 million, SGD 1 million and INR 596 million as of December 31, 2019. (2) In addition to the derivatives disclosed in the table, the Company enters into forward contracts to purchase when-issued mortgage-backed securities as part of its community reinvestment initiatives. At December 31, 2020, the Company had one outstanding contract with a total notional amount of $27 million and immaterial fair value. At December 31, 2019, the Company had two outstanding contracts with a total notional amount of $42 million and immaterial fair value. (3) Collateral amounts, which consist of both cash and investment securities, are limited to the related derivative asset/liability balance and do not include excess collateral received/pledged.
Schedule of Hedged Items in Fair Value Hedging Relationship	The following amounts were recorded on the statements of financial condition related to cumulative basis adjustments for fair value hedges (dollars in millions): December 31, 2020 December 31, 2019 Carrying Amount of Hedged Assets/Liabilities Cumulative Amount of Fair Value Hedging Adjustment Increasing the Carrying Amount of Hedged Assets/Liabilities Carrying Amount of Hedged Assets/Liabilities Cumulative Amount of Fair Value Hedging Adjustment Increasing the Carrying Amount of Hedged Assets/Liabilities Long-term borrowings $ 11,881 $ 281 $ 14,244 $ 13
Schedule of Impact of the Derivative Instruments on Income	The following table summarizes the impact of the derivative instruments on income and indicates where within the consolidated financial statements such impact is reported (dollars in millions): Location and Amount of (Losses) Gains Recognized in Income Interest Expense Other Income Deposits Long-Term Borrowings For the Year Ended December 31, 2020 Total amounts of income and expense line items presented in the statements of income in which the effects of fair value or cash flow hedges are recorded $ (1,231) $ (602) $ 56 The effects of cash flow and fair value hedging (Losses) Gains on cash flow hedging relationship Amounts reclassified from OCI into earnings $ (9) $ (3) $ — Gains (losses) on fair value hedging relationships Gains (losses) on hedged items $ — $ (268) $ — Gains on interest rate swaps — 423 — Total gains on fair value hedges $ — $ 155 $ — For the Year Ended December 31, 2019 Total amounts of income and expense line items presented in the statements of income in which the effects of fair value or cash flow hedges are recorded $ (1,587) $ (943) $ 93 The effects of cash flow and fair value hedging Gains on cash flow hedging relationship Amounts reclassified from OCI into earnings $ 3 $ 2 $ — Gains (losses) on fair value hedging relationships Gains (losses) on hedged items $ — $ (104) $ — Gains on interest rate swaps — 72 — Total gains (losses) on fair value hedges $ — $ (32) $ — The effects of derivatives not designated in hedging relationships Gains (losses) on derivatives not designated as hedges $ — $ — $ (1) Location and Amount of (Losses) Gains Recognized in Income Interest Expense Deposits Long-Term Borrowings Other Income For the Year Ended December 31, 2018 Total amounts of income and expense line items presented in the statements of income in which the effects of fair value or cash flow hedges are recorded $ (1,238) $ (901) $ 97 The effects of cash flow and fair value hedging Gains on cash flow hedging relationship Amounts reclassified from OCI into earnings $ — $ 6 $ — Gains (losses) on fair value hedging relationship Gains (losses) on hedged items $ — $ (18) $ — Gains (losses) on interest rate swaps — (23) — Total gains (losses) on fair value hedges $ — $ (41) $ — The effects of derivatives not designated in hedging relationships Gains on derivatives not designated as hedges $ — $ — $ 1

Segment Disclosures (Tables)

Segment Disclosures (Tables)	12 Months Ended
	Dec. 31, 2020
Segment Reporting [Abstract]
Schedule of Segment Disclosures	The following table presents segment data (dollars in millions): Digital Payment Total For the Year Ended December 31, 2020 Interest income Credit card loans $ 8,985 $ — $ 8,985 Private student loans 754 — 754 Personal loans 958 — 958 Other 398 — 398 Total interest income 11,095 — 11,095 Interest expense 1,865 — 1,865 Net interest income 9,230 — 9,230 Provision for credit losses 5,134 — 5,134 Other income 1,459 399 1,858 Other expense 4,292 227 4,519 Income before income tax expense $ 1,263 $ 172 $ 1,435 For the Year Ended December 31, 2019 Interest income Credit card loans $ 9,690 $ — $ 9,690 Private student loans 817 — 817 Personal loans 983 — 983 Other 502 1 503 Total interest income 11,992 1 11,993 Interest expense 2,530 — 2,530 Net interest income 9,462 1 9,463 Provision for credit losses (1) 3,233 (2) 3,231 Other income 1,648 348 1,996 Other expense 4,231 162 4,393 Income before income tax expense $ 3,646 $ 189 $ 3,835 For the Year Ended December 31, 2018 Interest income Credit card loans $ 8,835 $ — $ 8,835 Private student loans 753 — 753 Personal loans 935 — 935 Other 369 1 370 Total interest income 10,892 1 10,893 Interest expense 2,139 — 2,139 Net interest income 8,753 1 8,754 Provision for credit losses (1) 3,035 — 3,035 Other income 1,645 310 1,955 Other expense 3,918 159 4,077 Income before income tax expense $ 3,445 $ 152 $ 3,597 (1) Prior to the adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach.

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Schedule of Revenue from Contracts with Customers Disaggregated by Business Segment	The following table presents revenue from contracts with customers disaggregated by business segment and reconciles revenue from contracts with customers to total other income (dollars in millions): Digital Payment Total For the Year Ended December 31, 2020 Other income subject to ASC 606 Discount and interchange revenue, net (1) $ 871 $ 62 $ 933 Protection products revenue 180 — 180 Transaction processing revenue — 195 195 Other (loss) income (7) 63 56 Total other income subject to ASC 606 (2) 1,044 320 1,364 Other income not subject to ASC 606 Loan fee income 414 — 414 Other income 1 79 80 Total other income not subject to ASC 606 415 79 494 Total other income by operating segment $ 1,459 $ 399 $ 1,858 For the Year Ended December 31, 2019 Other income subject to ASC 606 Discount and interchange revenue, net (1) $ 1,000 $ 66 $ 1,066 Protection products revenue 194 — 194 Transaction processing revenue — 197 197 Other income 8 85 93 Total other income subject to ASC 606 (2) 1,202 348 1,550 Other income not subject to ASC 606 Loan fee income 449 — 449 Other (loss) income (3) — (3) Total other income not subject to ASC 606 446 — 446 Total other income by operating segment $ 1,648 $ 348 $ 1,996 For the Year Ended December 31, 2018 Other income subject to ASC 606 Discount and interchange revenue, net (1) $ 1,022 $ 52 $ 1,074 Protection products revenue 204 — 204 Transaction processing revenue — 178 178 Other income 17 80 97 Total other income subject to ASC 606 (2) 1,243 310 1,553 Other income not subject to ASC 606 Loan fee income 402 — 402 Total other income not subject to ASC 606 402 — 402 Total other income by operating segment $ 1,645 $ 310 $ 1,955 (1) Net of rewards, including Cashback Bonus rewards, of $1.9 billion, $1.9 billion and $1.8 billion for the years ended December 31, 2020, 2019 and 2018, respectively. (2) Excludes $2 million, $3 million and $3 million deposit product fees that are reported within net interest income for the years ended December 31, 2020, 2019 and 2018, respectively.

Parent Company Condensed Fina_2

Parent Company Condensed Financial Information (Tables) - Parent Company [Member]	12 Months Ended
	Dec. 31, 2020
Condensed Financial Statements, Captions [Line Items]
Schedule of Parent Company Condensed Statements of Financial Condition	The following Parent Company financial statements are provided in accordance with SEC rules, which require such disclosure when the restricted net assets of consolidated subsidiaries exceed 25% of consolidated net assets. Discover Financial Services (Parent Company Only) Condensed Statements of Financial Condition December 31, 2020 2019 (dollars in millions) Assets Cash and cash equivalents (1) $ 2,802 $ 2,511 Restricted cash 20 20 Notes receivable from subsidiaries (2) 891 877 Investments in bank subsidiaries 10,188 11,319 Investments in non-bank subsidiaries 727 820 Other assets 567 600 Total assets $ 15,195 $ 16,147 Liabilities and Stockholders’ Equity Non-interest bearing deposit accounts $ 2 $ 2 Short-term borrowings from subsidiaries 283 283 Long-term borrowings 3,673 3,636 Accrued expenses and other liabilities 353 367 Total liabilities 4,311 4,288 Stockholders’ equity 10,884 11,859 Total liabilities and stockholders’ equity $ 15,195 $ 16,147 (1) The Parent Company had $2.7 billion and $2.4 billion in a money market deposit account at Discover Bank as of December 31, 2020 and 2019, respectively, which is included in cash and cash equivalents. These funds are available to the Parent for liquidity purposes. (2) The Parent Company advanced $500 million to Discover Bank as of December 31, 2020 and 2019, which is included in notes receivable from subsidiaries. These funds are available to the Parent for liquidity purposes.
Schedule of Parent Company Condensed Statements of Income	Discover Financial Services (Parent Company Only) Condensed Statements of Income For the Years Ended December 31, 2020 2019 2018 (dollars in millions) Interest income $ 44 $ 82 $ 67 Interest expense 205 212 189 Net interest expense (161) (130) (122) Dividends from bank subsidiaries 555 2,530 2,375 Dividends from non-bank subsidiaries 200 100 450 Total income 594 2,500 2,703 Other expense (16) 1 — Income before income tax benefit and equity in undistributed net income of subsidiaries 610 2,499 2,703 Income tax benefit 30 25 33 Equity in undistributed net income of subsidiaries 501 433 6 Net income 1,141 2,957 2,742 Other comprehensive income, net 164 37 25 Comprehensive income $ 1,305 $ 2,994 $ 2,767
Schedule of Parent Company Condensed Statements of Cash Flows	Discover Financial Services (Parent Company Only) Condensed Statements of Cash Flows For the Years Ended December 31, 2020 2019 2018 (dollars in millions) Cash flows provided by operating activities Net income $ 1,141 $ 2,957 $ 2,742 Adjustments to reconcile net income to net cash provided by operating activities: Equity in undistributed net income of subsidiaries (501) (433) (6) Stock-based compensation expense 42 69 81 Deferred income taxes (5) (8) (5) Depreciation and amortization 41 38 34 Changes in assets and liabilities: Decrease (increase) in other assets 42 92 (416) (Decrease) increase in other liabilities and accrued expenses (30) 50 (129) Net cash provided by operating activities 730 2,765 2,301 Cash flows used for investing activities Decrease (increase) in investment in subsidiaries — — (3) Increase in loans to subsidiaries (15) (55) (62) Net cash used for investing activities (15) (55) (65) Cash flows used for financing activities Net increase (decrease) in short-term borrowings from subsidiaries — 42 (110) Proceeds from issuance of common stock 10 7 6 Proceeds from issuance of long-term borrowings — 595 49 Maturities and repayment of long-term borrowings (3) (86) (6) Purchases of treasury stock (348) (1,768) (2,065) Net increase (decrease) in deposits — (2) 1 Proceeds from issuance of preferred stock 493 — — Dividends paid on common and preferred stock (576) (573) (552) Net cash used for financing activities (424) (1,785) (2,677) Increase (decrease) in cash, cash equivalents and restricted cash 291 925 (441) Cash, cash equivalents and restricted cash, at beginning of period 2,531 1,606 2,047 Cash, cash equivalents and restricted cash, at end of period $ 2,822 $ 2,531 $ 1,606 Reconciliation of cash, cash equivalents and restricted cash Cash and cash equivalents $ 2,802 $ 2,511 $ 1,586 Restricted cash 20 20 20 Cash, cash equivalents and restricted cash, at end of period $ 2,822 $ 2,531 $ 1,606 Supplemental disclosure of cash flow information Cash paid during the period for: Interest expense $ 168 $ 170 $ 156 Income taxes, net of income tax refunds $ (31) $ 20 $ (22)

Quarterly Results (Tables)

Quarterly Results (Tables)	12 Months Ended
	Dec. 31, 2020
Quarterly Financial Data [Abstract]
Schedule of Quarterly Results	The following table provides unaudited quarterly results (dollars in millions, except per share data): December 31, 2020 September 30, 2020 June 30, 2020 March 31, 2020 December 31, 2019 September 30, 2019 June 30, 2019 March 31, 2019 Interest income $ 2,760 $ 2,681 $ 2,672 $ 2,982 $ 3,039 $ 3,040 $ 2,977 $ 2,937 Interest expense 383 416 482 584 615 638 645 632 Net interest income 2,377 2,265 2,190 2,398 2,424 2,402 2,332 2,305 Provision for credit losses 531 750 2,046 1,807 836 799 787 809 Other income 447 449 472 490 520 498 520 458 Other expense 1,278 1,005 1,077 1,159 1,184 1,107 1,078 1,024 Income (loss) before income tax expense 1,015 959 (461) (78) 924 994 987 930 Income tax expense (benefit) 216 188 (93) (17) 216 224 234 204 Net income (loss) $ 799 $ 771 $ (368) $ (61) $ 708 $ 770 $ 753 $ 726 Net income (loss) allocated to common stockholders (1) $ 794 $ 751 $ (369) $ (78) $ 704 $ 749 $ 747 $ 705 Basic earnings (loss) per common share (1) $ 2.59 $ 2.45 $ (1.20) $ (0.25) $ 2.25 $ 2.36 $ 2.32 $ 2.15 Diluted earnings (loss) per common share (1) $ 2.59 $ 2.45 $ (1.20) $ (0.25) $ 2.25 $ 2.36 $ 2.32 $ 2.15 (1) Because the inputs to net income allocated to common stockholders and earnings per share are calculated using weighted averages for the quarter, the sum of all four quarters may differ from the year to date amounts in the consolidated statements of income.

Background and Basis of Prese_3

Background and Basis of Presentation (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)segment		Jan. 01, 2020USD ($)	Dec. 31, 2019USD ($)		Dec. 31, 2018USD ($)	[3]	Dec. 31, 2017USD ($)	[3]
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of reportable segments | segment	2
Consolidation percentage	50.00%
Cost method investment ownership percentage	20.00%
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses	$ 8,226	[1],[2]	$ 5,844	$ 3,383	[1],[2],[3]	$ 3,041		$ 2,621
Other assets	3,586			2,459
Retained earnings	$ 19,955			$ 21,290
Accounting Standards Update 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses			2,500
Other assets			600
Retained earnings			$ (1,900)
[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 the adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Line Items]
Cash and due from banks	$ 1,100	$ 959
Interest-earning deposits in other banks	$ 12,500	6,000
Threshold charge-off period for bankruptcy and probate accounts	60 days
Fraudulent transaction charge off period	90 days
Off-Balance sheet, credit loss, liability	$ 0
Capitalized Computer Software, Gross	0
Impairment of intangible assets, indefinite-lived (excluding goodwill)	59
Advertising costs	212	264	$ 258
Deferred revenues related to balance transfer fees	62	67
Unamortized deferred costs for loan origination	157	178
Credit card rewards cost	1,900	1,900	$ 1,800
Liability for customer rewards	1,700	1,700
Unamortized portion of the deferred incentive payments	33	24
Trade Name and Other [Member]
Accounting Policies [Line Items]
Impairment of intangible assets, indefinite-lived (excluding goodwill)	$ 0	$ 0
Retirement Eligible [Member]
Accounting Policies [Line Items]
Amortization of share-based compensation in accordance with vesting terms	12 months
Building [Member]
Accounting Policies [Line Items]
Premises and equipment, useful life	39 years
Minimum [Member]
Accounting Policies [Line Items]
Delinquent loan qualification period	30 days
Minimum [Member] | Improvements [Member]
Accounting Policies [Line Items]
Premises and equipment, useful life	10 years
Minimum [Member] | Furniture and Fixtures [Member]
Accounting Policies [Line Items]
Premises and equipment, useful life	5 years
Minimum [Member] | Equipment [Member]
Accounting Policies [Line Items]
Premises and equipment, useful life	3 years
Minimum [Member] | Software Development [Member]
Accounting Policies [Line Items]
Premises and equipment, useful life	3 years
Maximum [Member]
Accounting Policies [Line Items]
Cash and cash equivalents maturity period	90 days
Maximum [Member] | Improvements [Member]
Accounting Policies [Line Items]
Premises and equipment, useful life	15 years
Maximum [Member] | Furniture and Fixtures [Member]
Accounting Policies [Line Items]
Premises and equipment, useful life	10 years
Maximum [Member] | Equipment [Member]
Accounting Policies [Line Items]
Premises and equipment, useful life	10 years
Maximum [Member] | Software Development [Member]
Accounting Policies [Line Items]
Premises and equipment, useful life	10 years
Credit Card Loans [Member]
Accounting Policies [Line Items]
Threshold charge-off period for past due accounts (in days)	180 days
Amortization period for loan origination costs	1 year
Personal And Private Student Loan Member [Member]
Accounting Policies [Line Items]
Threshold charge-off period for past due accounts (in days)	120 days

Investments (Narrative) (Detail

Investments (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)securities	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Investment Holdings [Line Items]
Available-for-sale investment securities, continuous unrealized loss position, number of securities | securities	0
Proceeds from sales of available-for-sale securities	$ 0	$ 0	$ 0
Recognized gains (losses) on available-for-sale securities	0	0	0
Taxable interest on investment securities	252	179	40
Tax exempt interest on investment securities	0	0	$ 0
Contingent liabilities related to equity method investments	0
Other Assets [Member] | Payment Services [Member]
Investment Holdings [Line Items]
Equity securities without readily determinable fair value	35	42
Other Assets [Member] | Community Reinvestment Act [Member]
Investment Holdings [Line Items]
Equity method investments	353	336
Investment related to affordable housing projects	324	298
Other Liabilities [Member] | Community Reinvestment Act [Member]
Investment Holdings [Line Items]
Contingent liabilities related to equity method investments	93	74
Contingent liabilities related to affordable housing project investments	$ 79	$ 59

Investments (Schedule of Invest

Investments (Schedule of Investment Securities) (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Investment Holdings [Line Items]
Other short-term investments		$ 2,200	$ 0
Investment securities		9,914	10,595
US Treasury Bill Securities [Member] | Asset Not Pledged as Collateral [Member]
Investment Holdings [Line Items]
Other short-term investments	[1]	2,200	0
U.S. Treasury Securities [Member]
Investment Holdings [Line Items]
Derivative collateral		117	121
U.S. Treasury Securities [Member] | Asset Not Pledged as Collateral [Member]
Investment Holdings [Line Items]
Investment securities	[2]	9,354	9,906
Residential Mortgage Backed Securities - Agency [Member]
Investment Holdings [Line Items]
Investment securities	[3]	$ 560	$ 689
[1]	Includes United States Treasury bills with maturity dates greater than 90 days but less than one year at the time of acquisition.
[2]	Includes $117 million and $121 million of United States Treasury securities pledged as swap collateral as of December 31, 2020 and 2019, respectively.
[3]	Consists of residential mortgage-backed securities issued by Fannie Mae, Freddie Mac and Ginnie Mae.

Investments (Schedule of Amorti

Investments (Schedule of Amortized Cost, Gross Unrealized Gains, Gross Unrealized Losses and Fair Value) (Details) - USD ($) $ in Millions		Dec. 31, 2020		Dec. 31, 2019
Investment Holdings [Line Items]
Available-for-sale investment securities, amortized cost	[1]	$ 9,277		$ 10,173
Available-for-sale investment securities, gross unrealized gains	[1]	377		158
Available-for-sale investment securities, gross unrealized losses	[1]	0		(8)
Available-for-sale investment securities, fair value	[1]	9,654		10,323
Held-to-maturity investment securities, amortized cost	[2]	260		272
Held-to-maturity investment securities, gross unrealized gains	[2]	9		3
Held-to-maturity investment securities, gross unrealized losses	[2]	0		(1)
Held-to-maturity investment securities, fair value	[2]	269		274
U.S. Treasury Securities [Member]
Investment Holdings [Line Items]
Available-for-sale investment securities, amortized cost	[1]	8,987		9,759
Available-for-sale investment securities, gross unrealized gains	[1]	367		155
Available-for-sale investment securities, gross unrealized losses	[1]	0		(8)
Available-for-sale investment securities, fair value	[1]	9,354		9,906
Residential Mortgage Backed Securities - Agency [Member]
Investment Holdings [Line Items]
Available-for-sale investment securities, amortized cost	[1]	290	[3]	414
Available-for-sale investment securities, gross unrealized gains	[1]	10		3
Available-for-sale investment securities, gross unrealized losses	[1]	0		0
Available-for-sale investment securities, fair value	[1]	300	[3]	417
Held-to-maturity investment securities, amortized cost	[2],[4]	260	[3]	272
Held-to-maturity investment securities, gross unrealized gains	[2],[4]	9		3
Held-to-maturity investment securities, gross unrealized losses	[2],[4]	0		(1)
Held-to-maturity investment securities, fair value	[2],[4]	$ 269	[3]	$ 274
[1]	Available-for-sale investment securities are reported at fair value.
[2]	Held-to-maturity investment securities are reported at amortized cost.
[3]	Maturities of residential mortgage-backed securities are reflective of the contractual maturities of the investment.
[4]	Amounts represent residential mortgage-backed securities that were classified as held-to-maturity as they were entered into as a part of the Company’s community reinvestment initiatives.

Investments (Schedule of Fair V

Investments (Schedule of Fair Value of Securities in a Continuous Unrealized Loss Position for Less Than 12 Months and More Than 12 Months) (Details) $ in Millions	Dec. 31, 2020securities	Dec. 31, 2019USD ($)securities
Investment Holdings [Line Items]
Available-for-sale investment securities, continuous unrealized loss position, number of securities | securities	0
U.S. Treasury Securities [Member]
Investment Holdings [Line Items]
Available-for-sale investment securities, continuous unrealized loss position, number of securities | securities		11
Available-for-sale investment securities, continuous unrealized loss position, less than 12 months, fair value		$ 1,402
Available-for-sale investment securities, continuous unrealized loss position, less than 12 months, unrealized losses		(8)
Available-for-sale investment securities, continuous unrealized loss position, more than 12 months, fair value		0
Available-for-sale investment securities, continuous unrealized loss position, more than 12 months, unrealized losses		$ 0
Residential Mortgage Backed Securities - Agency [Member]
Investment Holdings [Line Items]
Held-to-maturity investment securities, continuous unrealized loss position, number of securities | securities		58
Held-to-maturity investment securities, continuous unrealized loss position, less than 12 months, fair value		$ 64
Held-to-maturity investment securities, continuous unrealized loss position, less than 12 months, unrealized losses		0
Held-to-maturity investment securities, continuous unrealized loss position, more than 12 months, fair value		19
Held-to-maturity investment securities, continuous unrealized loss position, more than 12 months, unrealized losses		$ (1)

Investments (Schedule of Maturi

Investments (Schedule of Maturities and Weighted Average Yields of Available-for-Sale Debt Securities and Held-to-Maturity Debt Securities) (Details) - USD ($) $ in Millions		Dec. 31, 2020		Dec. 31, 2019
Investment Holdings [Line Items]
Available-for-sale investment securities, debt maturities, one year or less, amortized cost		$ 2,633
Available-for-sale investment securities, debt maturities, after one year through five years, amortized cost		6,399
Available-for-sale investment securities, debt maturities, after five years through ten years, amortized cost		235
Available-for-sale investment securities, debt maturities, after ten years, amortized cost		10
Available-for-sale investment securities, amortized cost	[1]	9,277		$ 10,173
Held-to-maturity investment securities, debt maturities, one year or less, amortized cost		0
Held-to-maturity investment securities, debt maturities, after one year through five years, amortized cost		0
Held-to-maturity investment securities, debt maturities, after five years through ten years, amortized cost		0
Held-to-maturity investment securities, debt maturities, after ten years, amortized cost		260
Held-to-maturity investment securities, amortized cost	[2]	260		272
Available-for-sale investment securities, debt maturities, one year or less, fair value		2,661
Available-for-sale investment securities, debt maturities, after one year through five years, fair value		6,740
Available-for-sale investment securities, debt maturities, after five years through ten years, fair value		243
Available-for-sale investment securities, debt maturities, after ten years, fair value		10
Available-for-sale investment securities, fair value	[1]	9,654		10,323
Held-to-maturity investment securities, debt maturities, one year or less, fair value		0
Held-to-maturity investment securities, debt maturities, after one year through five years, fair value		0
Held-to-maturity investment securities, debt maturities, after five years through ten years, fair value		0
Held-to-maturity investment securities, debt maturities, after ten years, fair value		269
Held-to-maturity investment securities, fair value	[2]	$ 269		274
Available-for-sale investment securities, debt maturities, one year or less, weighted-average yield	[3]	1.91%
Available-for-sale investment securities, debt maturities, after one year through five years, weighted-average yield	[3]	2.24%
Available-for-sale investment securities, debt maturities, after five years through ten years, weighted-average yield	[3]	2.07%
Available-for-sale investment securities, debt maturities, after ten years, weighted-average yield	[3]	0.99%
Available-for-sale investment securities, weighted-average yield	[3]	2.14%
Held-to-maturity investment securities, debt maturities, one year or less, weighted-average yield		0.00%
Held-to-maturity investment securities, debt maturities, after one year through five years, weighted-average yield		0.00%
Held-to-maturity investment securities, debt maturities, after five years though ten years, weighted-average yield		0.00%
Held-to-maturity investment securities, debt maturities, after ten years, weighted-average yield		3.13%
Held-to-maturity investment securities, weighted-average yield		3.13%
U.S. Treasury Securities [Member]
Investment Holdings [Line Items]
Available-for-sale investment securities, debt maturities, one year or less, amortized cost		$ 2,633
Available-for-sale investment securities, debt maturities, after one year through five years, amortized cost		6,354
Available-for-sale investment securities, debt maturities, after five years through ten years, amortized cost		0
Available-for-sale investment securities, debt maturities, after ten years, amortized cost		0
Available-for-sale investment securities, amortized cost	[1]	8,987		9,759
Available-for-sale investment securities, debt maturities, one year or less, fair value		2,661
Available-for-sale investment securities, debt maturities, after one year through five years, fair value		6,693
Available-for-sale investment securities, debt maturities, after five years through ten years, fair value		0
Available-for-sale investment securities, debt maturities, after ten years, fair value		0
Available-for-sale investment securities, fair value	[1]	$ 9,354		9,906
Available-for-sale investment securities, debt maturities, one year or less, weighted-average yield	[3]	1.91%
Available-for-sale investment securities, debt maturities, after one year through five years, weighted-average yield	[3]	2.25%
Available-for-sale investment securities, debt maturities, after five years through ten years, weighted-average yield	[3]	0.00%
Available-for-sale investment securities, debt maturities, after ten years, weighted-average yield	[3]	0.00%
Available-for-sale investment securities, weighted-average yield	[3]	2.15%
Residential Mortgage Backed Securities - Agency [Member]
Investment Holdings [Line Items]
Available-for-sale investment securities, debt maturities, one year or less, amortized cost	[4]	$ 0
Available-for-sale investment securities, debt maturities, after one year through five years, amortized cost	[4]	45
Available-for-sale investment securities, debt maturities, after five years through ten years, amortized cost	[4]	235
Available-for-sale investment securities, debt maturities, after ten years, amortized cost	[4]	10
Available-for-sale investment securities, amortized cost	[1]	290	[4]	414
Held-to-maturity investment securities, debt maturities, one year or less, amortized cost	[4]	0
Held-to-maturity investment securities, debt maturities, after one year through five years, amortized cost	[4]	0
Held-to-maturity investment securities, debt maturities, after five years through ten years, amortized cost	[4]	0
Held-to-maturity investment securities, debt maturities, after ten years, amortized cost	[4]	260
Held-to-maturity investment securities, amortized cost	[2],[5]	260	[4]	272
Available-for-sale investment securities, debt maturities, one year or less, fair value	[4]	0
Available-for-sale investment securities, debt maturities, after one year through five years, fair value	[4]	47
Available-for-sale investment securities, debt maturities, after five years through ten years, fair value	[4]	243
Available-for-sale investment securities, debt maturities, after ten years, fair value	[4]	10
Available-for-sale investment securities, fair value	[1]	300	[4]	417
Held-to-maturity investment securities, debt maturities, one year or less, fair value	[4]	0
Held-to-maturity investment securities, debt maturities, after one year through five years, fair value	[4]	0
Held-to-maturity investment securities, debt maturities, after five years through ten years, fair value	[4]	0
Held-to-maturity investment securities, debt maturities, after ten years, fair value	[4]	269
Held-to-maturity investment securities, fair value	[2],[5]	$ 269	[4]	$ 274
Available-for-sale investment securities, debt maturities, one year or less, weighted-average yield	[3]	0.00%
Available-for-sale investment securities, debt maturities, after one year through five years, weighted-average yield	[3]	1.62%
Available-for-sale investment securities, debt maturities, after five years through ten years, weighted-average yield	[3]	2.07%
Available-for-sale investment securities, debt maturities, after ten years, weighted-average yield	[3]	0.99%
Available-for-sale investment securities, weighted-average yield	[3]	1.97%
Held-to-maturity investment securities, debt maturities, one year or less, weighted-average yield		0.00%
Held-to-maturity investment securities, debt maturities, after one year through five years, weighted-average yield		0.00%
Held-to-maturity investment securities, debt maturities, after five years though ten years, weighted-average yield		0.00%
Held-to-maturity investment securities, debt maturities, after ten years, weighted-average yield		3.13%
Held-to-maturity investment securities, weighted-average yield		3.13%
[1]	Available-for-sale investment securities are reported at fair value.
[2]	Held-to-maturity investment securities are reported at amortized cost.
[3]	The weighted-average yield for available-for-sale investment securities is calculated based on the amortized cost.
[4]	Maturities of residential mortgage-backed securities are reflective of the contractual maturities of the investment.
[5]	Amounts represent residential mortgage-backed securities that were classified as held-to-maturity as they were entered into as a part of the Company’s community reinvestment initiatives.

Loan Receivables (Narrative) (D

Loan Receivables (Narrative) (Details) $ in Millions

Dec. 31, 2020USD ($)

Sep. 30, 2020

Jun. 30, 2020

Mar. 31, 2020

Jan. 01, 2020USD ($)

Dec. 31, 2020USD ($)segment

Dec. 31, 2020USD ($)

Dec. 31, 2019USD ($)

Dec. 31, 2018USD ($)

Dec. 31, 2017USD ($)

[3]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Number of loan portfolio segments (in segments) | segment

2

Allowance for credit losses

$ 8,226

[1],[2]

$ 5,844

$ 8,226

[1],[2]

$ 8,226

[1],[2]

$ 3,383

[1],[2],[3]

$ 3,041

[3]

$ 2,621

Allowance for credit loss, period increase (decrease)

$ 2,300

Expected future peak unemployment rate

8.70%

8.70%

8.70%

Expected future unemployment rate

8.20%

8.20%

8.20%

Expected future increase in GDP

2.70%

2.70%

2.70%

Financing receivable, allowance for credit loss, reasonable and supportable forecast period

18 months

18 months

18 months

12 months

Financing receivable, allowance for credit loss, reversion period

12 months

Percentage of defaulted loans that were charged off at the end of the month in which they defaulted (in percent)

53.00%

38.00%

36.00%

Accounting Standards Update 2016-13 [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Allowance for credit losses

2,500

Allowance for credit loss, period increase (decrease)

2,500

Minimum [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Delinquent loan qualification period

30 days

Credit Card Loans [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Allowance for credit losses

$ 6,491

$ 4,550

$ 6,491

$ 6,491

$ 2,883

[3]

$ 2,528

[3]

$ 2,147

Interest and fees forgiven due to credit card loan modification program

$ 66

73

$ 48

Personal Loans [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Temporary reduced payment program, maximum period of payment reduction

12 months

Maximum repayment term for temporary modification programs (in years)

9 years

Maximum repayment term for permanent modification programs (in years)

9 years

Private Student Loans [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Private student loans including PCI in repayment

5,700

$ 5,700

5,700

5,600

Student loans in forbearance

$ 117

$ 117

$ 117

$ 46

Credit Card Loans [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

Temporary reduced payment program, maximum period of payment reduction

12 months

Permanent workout program, maturity

60 months

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

Loan Receivables (Schedule of L

Loan Receivables (Schedule of Loan Receivables) (Details) - USD ($) $ in Millions		Dec. 31, 2020		Jan. 01, 2020	Dec. 31, 2019		Dec. 31, 2018	[3]	Dec. 31, 2017	[3]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables		$ 90,449			$ 95,894
Allowance for credit Loss		(8,226)	[1],[2]	$ (5,844)	(3,383)	[1],[2],[3]	$ (3,041)		$ (2,621)
Net loan receivables		82,223			92,511
Variable Interest Entity, Primary Beneficiary [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables		27,546			31,840
Allowance for credit Loss	[2]	(1,936)			(1,179)
Credit Card Securitization Trusts [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	[4]	27,296			31,548
Allowance for credit Loss	[4],[5]	(1,936)			(1,179)
Net loan receivables		25,360			30,369
Sellers' interest		10,575			12,652
Student Loan Securitization Trusts [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables		250			292
Credit Card Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	[6],[7]	71,472			77,181
Allowance for credit Loss		(6,491)		(4,550)	(2,883)	[3]	(2,528)		(2,147)
Interest Receivable		420			471
Credit Card Loans [Member] | Credit Card Securitization Trusts [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investors' interests		16,700			18,900
Sellers' interest		10,600			12,700
Total Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	[8]	18,977			18,713
Total Other Loans [Member] | Private Student Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	[8],[9]	9,954			9,653
Allowance for credit Loss		(840)		(653)	(148)	[3]	(169)		(162)
Interest Receivable		469			461
Total Other Loans [Member] | Private Student Loans [Member] | Student Loan Securitization Trusts [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans pledged as collateral		250			292
Total Other Loans [Member] | Personal Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	[8]	7,177			7,687
Allowance for credit Loss		(857)		(613)	(348)	[3]	(338)		(301)
Interest Receivable		49			53
Total Other Loans [Member] | Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	[8]	1,846			1,373
Allowance for credit Loss		(38)		$ (28)	(4)	[3]	$ (6)		$ (11)
Interest Receivable		$ 6			$ 4
[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 the adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach.
[4]	The Company maintains its allowance for credit losses at an amount equal to lifetime expected credit losses associated with all loan receivables, which includes all loan receivables in the trusts. Therefore, credit risk associated with the transferred receivables is fully reflected on the Company’s balance sheet in accordance with GAAP.
[5]	Prior to the adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach.
[6]	Amounts include carrying values of $16.7 billion and $18.9 billion underlying investors’ interest in trust debt at December 31, 2020 and 2019, respectively, and $10.6 billion and $12.7 billion in seller’s interest at December 31, 2020 and 2019, respectively. See Note 5: Credit Card and Student Loan Securitization Activities for additional information.
[7]	Unbilled accrued interest receivable on credit card loans, which is presented as part of other assets in the Company’s consolidated statements of financial condition, was $420 million and $471 million at December 31, 2020 and 2019, respectively.
[8]	Accrued interest receivable on private student, personal and other loans, which is presented as part of other assets in the Company’s consolidated statements of financial condition, was $469 million, $49 million and $6 million, respectively, at December 31, 2020 and $461 million, $53 million and $4 million, respectively, at December 31, 2019.
[9]	Amounts include carrying values of $250 million and $292 million in loans pledged as collateral against the note issued from a student loan securitization trust at December 31, 2020 and 2019, respectively. See Note 5: Credit Card and Student Loan Securitization Activities for additional information.

Loan Receivables (Schedule of C

Loan Receivables (Schedule of Credit Risk Profile by FICO Score and Origination Year) (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables		$ 90,449	$ 95,894
Revolving line-of-credit arrangements that were converted to term loans as a result of a TDR program, ending balance		1,000	956
Credit Card Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	[1],[2]	71,472	77,181
Credit Card Loans [Member] | FICO Score, 660 and Above [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables, credit card	[3]	$ 58,950	$ 61,997
FICO distribution %, credit card	[3]	82.00%	80.00%
Credit Card Loans [Member] | FICO Score, Less Than 660 Or No Score [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables, credit card	[3]	$ 12,522	$ 15,184
FICO distribution %, credit card	[3]	18.00%	20.00%
Total Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	[4]	$ 18,977	$ 18,713
Total Other Loans [Member] | Private Student Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	[4],[5]	9,954	9,653
Total Other Loans [Member] | Private Student Loans [Member] | FICO Score, 660 and Above [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables, year one, originated, current fiscal year	[6],[7]	$ 1,173
FICO distribution %, originated in current fiscal year	[6],[7]	95.00%
Loan receivable, year two, originated, fiscal year before current fiscal year	[6],[7]	$ 1,659	$ 1,176
FICO distribution %, originated in fiscal year before latest fiscal year	[6],[7]	96.00%	93.00%
Loan receivable, year three, originated, two years before current fiscal year	[6],[7]	$ 1,365	$ 1,518
FICO distribution %, originated two years before latest fiscal year	[6],[7]	96.00%	95.00%
Loan receivable, year four, originated, three years before current fiscal year	[6],[7]	$ 1,052	$ 1,198
FICO distribution %, originated three years before latest fiscal year	[6],[7]	95.00%	95.00%
Loan receivable, year five, originated, four years before current fiscal year	[6],[7]	$ 797	$ 934
FICO distribution %, originated four years before latest fiscal year	[6],[7]	94.00%	94.00%
Loan receivable, originated, more than five years before current fiscal year	[6],[7]	$ 3,422	$ 4,229
FICO distribution %, originated five or more years before latest fiscal year	[6],[7]	94.00%	93.00%
Loan receivables	[6],[7]	$ 9,468	$ 9,055
FICO scores as a percentage of loan receivables	[6],[7]	95.00%	94.00%
Total Other Loans [Member] | Private Student Loans [Member] | FICO Score, Less Than 660 Or No Score [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables, year one, originated, current fiscal year	[6],[7]	$ 60
FICO distribution %, originated in current fiscal year	[6],[7]	5.00%
Loan receivable, year two, originated, fiscal year before current fiscal year	[6],[7]	$ 61	$ 92
FICO distribution %, originated in fiscal year before latest fiscal year	[6],[7]	4.00%	7.00%
Loan receivable, year three, originated, two years before current fiscal year	[6],[7]	$ 61	$ 79
FICO distribution %, originated two years before latest fiscal year	[6],[7]	4.00%	5.00%
Loan receivable, year four, originated, three years before current fiscal year	[6],[7]	$ 57	$ 69
FICO distribution %, originated three years before latest fiscal year	[6],[7]	5.00%	5.00%
Loan receivable, year five, originated, four years before current fiscal year	[6],[7]	$ 47	$ 58
FICO distribution %, originated four years before latest fiscal year	[6],[7]	6.00%	6.00%
Loan receivable, originated, more than five years before current fiscal year	[6],[7]	$ 200	$ 300
FICO distribution %, originated five or more years before latest fiscal year	[6],[7]	6.00%	7.00%
Loan receivables	[6],[7]	$ 486	$ 598
FICO scores as a percentage of loan receivables	[6],[7]	5.00%	6.00%
Total Other Loans [Member] | Personal Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	[4]	$ 7,177	$ 7,687
Total Other Loans [Member] | Personal Loans [Member] | FICO Score, 660 and Above [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables, year one, originated, current fiscal year		$ 2,880
FICO distribution %, originated in current fiscal year		99.00%
Loan receivable, year two, originated, fiscal year before current fiscal year		$ 2,183	$ 3,529
FICO distribution %, originated in fiscal year before latest fiscal year		96.00%	98.00%
Loan receivable, year three, originated, two years before current fiscal year		$ 1,018	$ 1,941
FICO distribution %, originated two years before latest fiscal year		92.00%	93.00%
Loan receivable, year four, originated, three years before current fiscal year		$ 558	$ 1,167
FICO distribution %, originated three years before latest fiscal year		89.00%	90.00%
Loan receivable, year five, originated, four years before current fiscal year		$ 189	$ 475
FICO distribution %, originated four years before latest fiscal year		87.00%	88.00%
Loan receivable, originated, more than five years before current fiscal year		$ 38	$ 145
FICO distribution %, originated five or more years before latest fiscal year		81.00%	84.00%
Loan receivables		$ 6,866	$ 7,257
FICO scores as a percentage of loan receivables		96.00%	94.00%
Total Other Loans [Member] | Personal Loans [Member] | FICO Score, Less Than 660 Or No Score [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables, year one, originated, current fiscal year		$ 25
FICO distribution %, originated in current fiscal year		1.00%
Loan receivable, year two, originated, fiscal year before current fiscal year		$ 90	$ 62
FICO distribution %, originated in fiscal year before latest fiscal year		4.00%	2.00%
Loan receivable, year three, originated, two years before current fiscal year		$ 90	$ 140
FICO distribution %, originated two years before latest fiscal year		8.00%	7.00%
Loan receivable, year four, originated, three years before current fiscal year		$ 69	$ 136
FICO distribution %, originated three years before latest fiscal year		11.00%	10.00%
Loan receivable, year five, originated, four years before current fiscal year		$ 28	$ 65
FICO distribution %, originated four years before latest fiscal year		13.00%	12.00%
Loan receivable, originated, more than five years before current fiscal year		$ 9	$ 27
FICO distribution %, originated five or more years before latest fiscal year		19.00%	16.00%
Loan receivables		$ 311	$ 430
FICO scores as a percentage of loan receivables		4.00%	6.00%
[1]	Amounts include carrying values of $16.7 billion and $18.9 billion underlying investors’ interest in trust debt at December 31, 2020 and 2019, respectively, and $10.6 billion and $12.7 billion in seller’s interest at December 31, 2020 and 2019, respectively. See Note 5: Credit Card and Student Loan Securitization Activities for additional information.
[2]	Unbilled accrued interest receivable on credit card loans, which is presented as part of other assets in the Company’s consolidated statements of financial condition, was $420 million and $471 million at December 31, 2020 and 2019, respectively.
[3]	Amounts include $1.0 billion and $956 million of revolving line-of-credit arrangements that were converted to term loans as a result of a TDR program as of December 31, 2020 and 2019, respectively.
[4]	Accrued interest receivable on private student, personal and other loans, which is presented as part of other assets in the Company’s consolidated statements of financial condition, was $469 million, $49 million and $6 million, respectively, at December 31, 2020 and $461 million, $53 million and $4 million, respectively, at December 31, 2019.
[5]	Amounts include carrying values of $250 million and $292 million in loans pledged as collateral against the note issued from a student loan securitization trust at December 31, 2020 and 2019, respectively. See Note 5: Credit Card and Student Loan Securitization Activities for additional information.
[6]	A majority of student loan originations occur in the third quarter and disbursements can span multiple calendar years.
[7]	FICO score represents the higher credit score of the cosigner or borrower

Loan Receivables (Schedule of D

Loan Receivables (Schedule of Delinquent Loans by Origination Year) (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Loan receivables		$ 90,449	$ 95,894
Credit Card Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan receivables	[1],[2]	71,472	77,181
Credit Card Loans [Member] | 30-89 Days Delinquent [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan receivables, credit card		739	999
Credit Card Loans [Member] | 90 or More Days Delinquent [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan receivables, credit card		739	1,020
Credit Card Loans [Member] | Financing Receivables, Equal to or Greater than 30 Days Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan receivables, credit card		1,478	2,019
Total Other Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan receivables	[3]	18,977	18,713
Total Other Loans [Member] | Private Student Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan receivables	[3],[4]	9,954	9,653
Total Other Loans [Member] | Personal Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan receivables	[3]	7,177	7,687
Total Other Loans [Member] | 30-89 Days Delinquent [Member] | Private Student Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan receivables, year one, originated, current fiscal year	[5],[6]	0
Loan receivable, year two, originated, fiscal year before current fiscal year	[5],[6]	3	0
Loan receivable, year three, originated, two years before current fiscal year	[5],[6]	9	4
Loan receivable, year four, originated, three years before current fiscal year	[5],[6]	12	11
Loan receivable, year five, originated, four years before current fiscal year	[5],[6]	14	14
Loan receivable, originated, more than five years before current fiscal year	[5],[6]	72	106
Loan receivables	[5],[6]	110	135
Total Other Loans [Member] | 30-89 Days Delinquent [Member] | Personal Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan receivables, year one, originated, current fiscal year		5
Loan receivable, year two, originated, fiscal year before current fiscal year		18	11
Loan receivable, year three, originated, two years before current fiscal year		15	27
Loan receivable, year four, originated, three years before current fiscal year		10	22
Loan receivable, year five, originated, four years before current fiscal year		4	10
Loan receivable, originated, more than five years before current fiscal year		1	4
Loan receivables		53	74
Total Other Loans [Member] | 90 or More Days Delinquent [Member] | Private Student Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan receivables, year one, originated, current fiscal year	[5],[6]	0
Loan receivable, year two, originated, fiscal year before current fiscal year	[5],[6]	1	0
Loan receivable, year three, originated, two years before current fiscal year	[5],[6]	3	1
Loan receivable, year four, originated, three years before current fiscal year	[5],[6]	4	3
Loan receivable, year five, originated, four years before current fiscal year	[5],[6]	3	5
Loan receivable, originated, more than five years before current fiscal year	[5],[6]	17	37
Loan receivables	[5],[6]	28	46
Total Other Loans [Member] | 90 or More Days Delinquent [Member] | Personal Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan receivables, year one, originated, current fiscal year		2
Loan receivable, year two, originated, fiscal year before current fiscal year		9	3
Loan receivable, year three, originated, two years before current fiscal year		7	11
Loan receivable, year four, originated, three years before current fiscal year		5	10
Loan receivable, year five, originated, four years before current fiscal year		1	5
Loan receivable, originated, more than five years before current fiscal year		1	2
Loan receivables		25	31
Total Other Loans [Member] | Financing Receivables, Equal to or Greater than 30 Days Past Due [Member] | Private Student Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan receivables, year one, originated, current fiscal year	[5],[6]	0
Loan receivable, year two, originated, fiscal year before current fiscal year	[5],[6]	4	0
Loan receivable, year three, originated, two years before current fiscal year	[5],[6]	12	5
Loan receivable, year four, originated, three years before current fiscal year	[5],[6]	16	14
Loan receivable, year five, originated, four years before current fiscal year	[5],[6]	17	19
Loan receivable, originated, more than five years before current fiscal year	[5],[6]	89	143
Loan receivables	[5],[6]	138	181
Total Other Loans [Member] | Financing Receivables, Equal to or Greater than 30 Days Past Due [Member] | Personal Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Loan receivables, year one, originated, current fiscal year		7
Loan receivable, year two, originated, fiscal year before current fiscal year		27	14
Loan receivable, year three, originated, two years before current fiscal year		22	38
Loan receivable, year four, originated, three years before current fiscal year		15	32
Loan receivable, year five, originated, four years before current fiscal year		5	15
Loan receivable, originated, more than five years before current fiscal year		2	6
Loan receivables		$ 78	$ 105
[1]	Amounts include carrying values of $16.7 billion and $18.9 billion underlying investors’ interest in trust debt at December 31, 2020 and 2019, respectively, and $10.6 billion and $12.7 billion in seller’s interest at December 31, 2020 and 2019, respectively. See Note 5: Credit Card and Student Loan Securitization Activities for additional information.
[2]	Unbilled accrued interest receivable on credit card loans, which is presented as part of other assets in the Company’s consolidated statements of financial condition, was $420 million and $471 million at December 31, 2020 and 2019, respectively.
[3]	Accrued interest receivable on private student, personal and other loans, which is presented as part of other assets in the Company’s consolidated statements of financial condition, was $469 million, $49 million and $6 million, respectively, at December 31, 2020 and $461 million, $53 million and $4 million, respectively, at December 31, 2019.
[4]	Amounts include carrying values of $250 million and $292 million in loans pledged as collateral against the note issued from a student loan securitization trust at December 31, 2020 and 2019, respectively. See Note 5: Credit Card and Student Loan Securitization Activities for additional information.
[5]	Includes PCD loans for all periods presented.
[6]	Student loans may include a deferment period, during which customers are not required to make payments while enrolled in school at least half time as determined by the school. During a deferment period, these loans do not advance into delinquency.

Loan Receivables (Schedule of_2

Loan Receivables (Schedule of Changes in the Allowance for Credit Losses) (Details) - USD ($) $ in Millions		Jan. 01, 2020		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit Loss, balance at beginning of period	[3]	$ 3,383	[1],[2]	$ 3,383	[1],[2]	$ 3,041		$ 2,621
Cumulative Effect of ASU No. 2016-13 Adoption	[4]	2,461
Provision for credit losses				5,117	[5]	3,231	[3]	3,035	[3]
Charge-offs				(3,476)		(3,617)		(3,182)
Recoveries				741		731		570
Net charge-offs				(2,735)		(2,886)	[6]	(2,612)	[6]
Financing receivable, allowance for credit Loss, other adjustment	[7]					(3)		(3)
Allowance for credit Loss, balance at end of period		5,844		8,226	[1],[2]	3,383	[1],[2],[3]	3,041	[3]
Credit loss build (release) on unfunded commitments				17
Credit Card Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit Loss, balance at beginning of period	[3]	2,883		2,883		2,528		2,147
Cumulative Effect of ASU No. 2016-13 Adoption	[4]	1,667
Provision for credit losses				4,379	[5]	2,849	[3]	2,594	[3]
Charge-offs				(3,101)		(3,165)		(2,734)
Recoveries				663		671		521
Net charge-offs				(2,438)		(2,494)	[6]	(2,213)	[6]
Financing receivable, allowance for credit Loss, other adjustment	[7]					0		0
Allowance for credit Loss, balance at end of period		4,550		6,491		2,883	[3]	2,528	[3]
Total Other Loans [Member] | Private Student Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit Loss, balance at beginning of period	[3]	148		148		169		162
Cumulative Effect of ASU No. 2016-13 Adoption	[4]	505
Provision for credit losses				251	[5]	51	[3]	95	[3]
Charge-offs				(85)		(82)		(97)
Recoveries				21		13		12
Net charge-offs				(64)		(69)	[6]	(85)	[6]
Financing receivable, allowance for credit Loss, other adjustment	[7]					(3)		(3)
Allowance for credit Loss, balance at end of period		653		840		148	[3]	169	[3]
Total Other Loans [Member] | Personal Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit Loss, balance at beginning of period	[3]	348		348		338		301
Cumulative Effect of ASU No. 2016-13 Adoption	[4]	265
Provision for credit losses				476	[5]	332	[3]	345	[3]
Charge-offs				(289)		(369)		(345)
Recoveries				57		47		37
Net charge-offs				(232)		(322)	[6]	(308)	[6]
Financing receivable, allowance for credit Loss, other adjustment	[7]					0		0
Allowance for credit Loss, balance at end of period		613		857		348	[3]	338	[3]
Total Other Loans [Member] | Other Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit Loss, balance at beginning of period	[3]	4		4		6		11
Cumulative Effect of ASU No. 2016-13 Adoption	[4]	24
Provision for credit losses				11	[5]	(1)	[3]	1	[3]
Charge-offs				(1)		(1)		(6)
Recoveries				0		0		0
Net charge-offs				(1)		(1)	[6]	(6)	[6]
Financing receivable, allowance for credit Loss, other adjustment	[7]					0		0
Allowance for credit Loss, balance at end of period		$ 28		$ 38		$ 4	[3]	$ 6	[3]
[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 the adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach.
[4]	Represents the adjustment to the allowance for credit losses as a result of the adoption of ASU No. 2016-13 on January 1, 2020.
[5]	Excludes a $17 million build of the liability for expected credit losses on unfunded commitments for the year ended December 31, 2020, as the liability is recorded in accrued expenses and other liabilities in the Company’s consolidated statements of financial condition.
[6]	Prior to the 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)

Loan Receivables (Schedule of N

Loan Receivables (Schedule of Net Charge-offs of Interest and Fee Revenues on Loan Receivables) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Receivables [Abstract]
Interest and fees accrued subsequently charged off, net of recoveries (recorded as a reduction of interest income)	$ 484	$ 515	$ 442
Fees accrued subsequently charged off, net of recoveries (recorded as a reduction to other income)	$ 117	$ 123	$ 109

Loan Receivables (Schedule of_3

Loan Receivables (Schedule of Delinquent and Non-Accruing Loans) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		$ 1,705	$ 2,312
Loan receivables, 90 or more days delinquent and accruing		737	1,014
Loan receivables, total non-accruing	[1]	243	266
30-89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		910	1,213
90 or More Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		795	1,099
Credit Card Loans [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		1,478	2,019
Loan receivables, 90 or more days delinquent and accruing		687	940
Loan receivables, total non-accruing	[1]	209	237
Estimated gross interest income that would have been recorded based on original terms		33	45	$ 41
Credit Card Loans [Member] | 30-89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		739	999
Credit Card Loans [Member] | 90 or More Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		739	1,020
Total Other Loans [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		227	293
Loan receivables, 90 or more days delinquent and accruing		50	74
Loan receivables, total non-accruing	[1]	34	29
Total Other Loans [Member] | 30-89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		171	214
Total Other Loans [Member] | 90 or More Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		56	79
Total Other Loans [Member] | Private Student Loans [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due	[2]	138	181
Loan receivables, 90 or more days delinquent and accruing	[2]	27	45
Loan receivables, total non-accruing	[1],[2]	12	11
Total Other Loans [Member] | Private Student Loans [Member] | 30-89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due	[2]	110	135
Total Other Loans [Member] | Private Student Loans [Member] | 90 or More Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due	[2]	28	46
Total Other Loans [Member] | Personal Loans [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		78	105
Loan receivables, 90 or more days delinquent and accruing		23	29
Loan receivables, total non-accruing	[1]	12	12
Total Other Loans [Member] | Personal Loans [Member] | 30-89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		53	74
Total Other Loans [Member] | Personal Loans [Member] | 90 or More Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		25	31
Total Other Loans [Member] | Other Loans [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		11	7
Loan receivables, 90 or more days delinquent and accruing		0	0
Loan receivables, total non-accruing	[1]	10	6
Total Other Loans [Member] | Other Loans [Member] | 30-89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		8	5
Total Other Loans [Member] | Other Loans [Member] | 90 or More Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		$ 3	$ 2
[1]	The Company estimates that the gross interest income that would have been recorded in accordance with the original terms of non-accruing credit card loans was $33 million, $45 million and $41 million for the years ended December 31, 2020, 2019 and 2018, respectively. The Company does not separately track the amount of gross interest income that would have been recorded in accordance with the original terms of loans. This amount was estimated based on customers’ current balances and most recent interest rates.
[2]	Includes PCD loans for all periods presented

Loan Receivables (Schedule of_4

Loan Receivables (Schedule of Loans That Entered a Modification Program During the Period) (Details) $ in Millions		12 Months Ended
		Dec. 31, 2020USD ($)accounts	Dec. 31, 2019USD ($)accounts	Dec. 31, 2018USD ($)accounts
Credit Card Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Accounts that entered a loan modification program during the period, number of accounts | accounts	[1]	152,055	368,009	268,817
Accounts that entered a loan modification program during the period, balances	[1]	$ 1,022	$ 2,364	$ 1,713
Financing Receivables Modifications Entering Program, Converted from Revolving Line-of-Credit Arrangement to Term Loan		$ 670	$ 741	$ 491
Total Other Loans [Member] | Private Student Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Accounts that entered a loan modification program during the period, number of accounts | accounts		1,916	6,742	4,057
Accounts that entered a loan modification program during the period, balances		$ 35	$ 124	$ 74
Total Other Loans [Member] | Personal Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Accounts that entered a loan modification program during the period, number of accounts | accounts		8,805	10,945	8,260
Accounts that entered a loan modification program during the period, balances		$ 114	$ 147	$ 111
[1]	Accounts that entered a credit card TDR program include $670 million, $741 million and $491 million that were converted from revolving line-of-credit arrangements to term loans during the years ended December 31, 2020, 2019 and 2018, respectively.

Loan Receivables (Schedule of T

Loan Receivables (Schedule of Troubled Debt Restructurings That Subsequently Defaulted) (Details) $ in Millions		12 Months Ended
		Dec. 31, 2020USD ($)missed_paymentsaccounts	Dec. 31, 2019USD ($)accounts	Dec. 31, 2018USD ($)accounts
Credit Card Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings that subsequently defaulted, number of accounts | accounts	[1],[2]	48,075	71,326	42,659
Troubled debt restructurings that subsequently defaulted, aggregated outstanding balances upon default | $	[1],[2]	$ 276	$ 410	$ 239
Amount of missed payments after which a customer defaults from a modification program (in payments) | missed_payments		2
Total Other Loans [Member] | Private Student Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings that subsequently defaulted, number of accounts | accounts	[3]	1,119	1,406	1,041
Troubled debt restructurings that subsequently defaulted, aggregated outstanding balances upon default | $	[3]	$ 22	$ 27	$ 19
Delinquency days to default (in days)		60 days
Total Other Loans [Member] | Personal Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings that subsequently defaulted, number of accounts | accounts	[1]	3,145	4,152	2,955
Troubled debt restructurings that subsequently defaulted, aggregated outstanding balances upon default | $	[1]	$ 46	$ 59	$ 40
Amount of missed payments after which a customer defaults from a modification program (in payments) | missed_payments		2
[1]	For credit card loans and personal loans, a customer defaults from a modification program either after two consecutive missed payments or at charge-off, depending on the program. The outstanding balance upon default is generally the loan balance at the end of the month prior to default.
[2]	Terms revert back to the pre-modification terms for customers who default from a temporary program and charging privileges remain suspended in most cases.
[3]	For student loans, defaults have been defined as loans that are 60 or more days delinquent. The outstanding balance upon default is generally the loan balance at the end of the month prior to default.

Loan Recievables (Schedule of G

Loan Recievables (Schedule of Geographic Distribution of Loan Receivables) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Credit Card Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 71,472	$ 77,181
Percentage of total loan receivables (in percent)	100.00%	100.00%
Credit Card Loans [Member] | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 6,273	$ 7,110
Percentage of total loan receivables (in percent)	8.80%	9.20%
Credit Card Loans [Member] | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 6,182	$ 6,543
Percentage of total loan receivables (in percent)	8.60%	8.50%
Credit Card Loans [Member] | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 4,931	$ 5,176
Percentage of total loan receivables (in percent)	6.90%	6.70%
Credit Card Loans [Member] | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 4,836	$ 5,335
Percentage of total loan receivables (in percent)	6.80%	6.90%
Credit Card Loans [Member] | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 3,714	$ 4,084
Percentage of total loan receivables (in percent)	5.20%	5.30%
Credit Card Loans [Member] | Pennsylvania
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 3,616	$ 3,873
Percentage of total loan receivables (in percent)	5.10%	5.00%
Credit Card Loans [Member] | Ohio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 3,005	$ 3,207
Percentage of total loan receivables (in percent)	4.20%	4.20%
Credit Card Loans [Member] | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 2,558	$ 2,807
Percentage of total loan receivables (in percent)	3.60%	3.60%
Credit Card Loans [Member] | Georgia
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 2,204	$ 2,325
Percentage of total loan receivables (in percent)	3.10%	3.00%
Credit Card Loans [Member] | Michigan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 1,983	$ 2,165
Percentage of total loan receivables (in percent)	2.80%	2.80%
Credit Card Loans [Member] | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 32,170	$ 34,556
Percentage of total loan receivables (in percent)	44.90%	44.80%
Total Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 18,977	$ 18,713
Percentage of total loan receivables (in percent)	100.00%	100.00%
Total Other Loans [Member] | California
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 1,706	$ 1,764
Percentage of total loan receivables (in percent)	9.00%	9.40%
Total Other Loans [Member] | Texas
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 1,224	$ 1,151
Percentage of total loan receivables (in percent)	6.40%	6.20%
Total Other Loans [Member] | Florida
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 975	$ 930
Percentage of total loan receivables (in percent)	5.10%	5.00%
Total Other Loans [Member] | New York
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 1,797	$ 1,859
Percentage of total loan receivables (in percent)	9.50%	9.90%
Total Other Loans [Member] | Illinois
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 1,163	$ 1,157
Percentage of total loan receivables (in percent)	6.10%	6.20%
Total Other Loans [Member] | Pennsylvania
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 1,317	$ 1,275
Percentage of total loan receivables (in percent)	6.90%	6.80%
Total Other Loans [Member] | Ohio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 758	$ 739
Percentage of total loan receivables (in percent)	4.00%	4.00%
Total Other Loans [Member] | New Jersey
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 1,002	$ 980
Percentage of total loan receivables (in percent)	5.30%	5.20%
Total Other Loans [Member] | Michigan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 585	$ 585
Percentage of total loan receivables (in percent)	3.10%	3.10%
Total Other Loans [Member] | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 7,862	$ 7,679
Percentage of total loan receivables (in percent)	41.50%	41.00%
Total Other Loans [Member] | Massachusetts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables	$ 588	$ 594
Percentage of total loan receivables (in percent)	3.10%	3.20%

Credit Card and Student Loan _3

Credit Card and Student Loan Securitization Activities (Narrative) (Details)	12 Months Ended
	Dec. 31, 2020classes
Variable Interest Entity, Primary Beneficiary [Member] | Discover Card Execution Note Trust [Member] | Credit Card Securitization Trusts [Member]
Variable Interest Entity [Line Items]
Number of classes of securities in debt structure (in classes)	4

Credit Card and Student Loan _4

Credit Card and Student Loan Securitization Activities (Schedule of Restricted Credit Card Securitized Assets) (Details) - USD ($) $ in Millions		Dec. 31, 2020		Jan. 01, 2020	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017	[3]
Variable Interest Entity [Line Items]
Restricted cash		$ 25			$ 40		$ 1,846
Loan receivables		90,449			95,894
Allowance for credit Loss		(8,226)	[1],[2]	$ (5,844)	(3,383)	[1],[2],[3]	$ (3,041)	[3]	$ (2,621)
Net loan receivables		82,223			92,511
Other		3,586			2,459
Total assets		112,889			113,996
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Restricted cash		25			40
Loan receivables		27,546			31,840
Allowance for credit Loss	[2]	(1,936)			(1,179)
Other		4			5
Variable Interest Entity, Primary Beneficiary [Member] | Credit Card Securitization Trusts [Member]
Variable Interest Entity [Line Items]
Restricted cash		16			28
Investors’ interests held by third-party investors		10,600			14,100
Investors’ interests held by wholly-owned subsidiaries of Discover Bank		6,121			4,796
Seller’s interest		10,575			12,652
Loan receivables	[4]	27,296			31,548
Allowance for credit Loss	[4],[5]	(1,936)			(1,179)
Net loan receivables		25,360			30,369
Other		3			5
Total assets		$ 25,379			$ 30,402
[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 the adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach.
[4]	The Company maintains its allowance for credit losses at an amount equal to lifetime expected credit losses associated with all loan receivables, which includes all loan receivables in the trusts. Therefore, credit risk associated with the transferred receivables is fully reflected on the Company’s balance sheet in accordance with GAAP.
[5]	Prior to the adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach.

Credit Card and Student Loan _5

Credit Card and Student Loan Securitization Activities (Schedule of Restricted Student Loan Securitized Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Restricted cash	$ 25	$ 40	$ 1,846
Loan receivables	90,449	95,894
Total assets	112,889	113,996
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Restricted cash	25	40
Loan receivables	27,546	31,840
Variable Interest Entity, Primary Beneficiary [Member] | Student Loan Securitization Trusts [Member]
Variable Interest Entity [Line Items]
Restricted cash	9	12
Loan receivables	250	292
Total assets	$ 259	$ 304

Premises and Equipment (Narrati

Premises and Equipment (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 98	$ 84	$ 75
Amortization expense on capitalized software	$ 100	$ 80	$ 67

Premises and Equipment (Schedul

Premises and Equipment (Schedule of Premises and Equipment) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 2,737	$ 2,668
Premises and equipment, net	1,027	1,057
Land [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	38	42
Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	673	693
Furniture, Fixtures and Equipment [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	1,125	1,082
Software [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	901	851
Less: accumulated depreciation and accumulated amortization of software	(361)	(335)
Premises and Equipment Excluding Software [Member]
Property, Plant and Equipment [Line Items]
Less: accumulated depreciation and accumulated amortization of software	$ (1,349)	$ (1,276)

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Line Items]
Goodwill		$ 255	$ 255
Impairment of intangible assets, indefinite-lived (excluding goodwill)		59
Intangible assets, net		95	155
Trade Name and Other [Member]
Goodwill [Line Items]
Impairment of intangible assets, indefinite-lived (excluding goodwill)		0	0
Payment Services [Member]
Goodwill [Line Items]
Goodwill		255	$ 255
Goodwill impairment charge		0
Payment Services [Member] | Trade Name and Other [Member]
Goodwill [Line Items]
Impairment of intangible assets, indefinite-lived (excluding goodwill)	$ 36
Intangible assets, net		92
Payment Services [Member] | International Transaction Processing Rights [Member]
Goodwill [Line Items]
Impairment of intangible assets, indefinite-lived (excluding goodwill)	$ 23
Intangible assets, net		$ 0

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets (Schedule of Intangible Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Finite Lived And Indefinite Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross carrying amount	$ 77	$ 77
Amortizable intangible assets, accumulated amortization	74	73
Amortizable intangible assets, net book value	3	4
Non-amortizable intangible assets, gross carrying amount and net book value	92	151
Total intangible assets, gross carrying amount	169	228
Total intangible assets, net book value	95	155
Trade Name and Other [Member]
Finite Lived And Indefinite Lived Intangible Assets [Line Items]
Non-amortizable intangible assets, gross carrying amount and net book value	92	128
International Transaction Processing Rights [Member]
Finite Lived And Indefinite Lived Intangible Assets [Line Items]
Non-amortizable intangible assets, gross carrying amount and net book value	0	23
Customer Relationships [Member]
Finite Lived And Indefinite Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross carrying amount	69	69
Amortizable intangible assets, accumulated amortization	69	68
Amortizable intangible assets, net book value	0	1
Trade Name and Other [Member]
Finite Lived And Indefinite Lived Intangible Assets [Line Items]
Amortizable intangible assets, gross carrying amount	8	8
Amortizable intangible assets, accumulated amortization	5	5
Amortizable intangible assets, net book value	$ 3	$ 3

Deposits (Narrative) (Details)

Deposits (Narrative) (Details)	12 Months Ended
	Dec. 31, 2020channels
Deposits [Abstract]
Deposits source channels (in number of channels)	2

Deposits (Schedule of Interest

Deposits (Schedule of Interest Bearing Deposit Accounts) (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Deposits [Abstract]
Certificates of deposit in amounts less than $100,000		$ 19,105	$ 25,113
Certificates of deposit in amounts $100,000 or greater	[1]	9,164	9,268
Savings deposits, including money market deposit accounts		47,426	37,574
Total interest-bearing deposits		75,695	71,955
Certificates of deposit equal to or greater than $250,000		$ 2,600	$ 2,600
[1]	Includes $2.6 billion in certificates of deposit equal to or greater than $250,000, the Federal Deposit Insurance Corporation (“FDIC”) insurance limit, as of December 31, 2020 and 2019.

Deposits (Schedule of $100,000

Deposits (Schedule of $100,000 or More Certificates of Deposit Maturities) (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Deposits [Abstract]
Three months or less		$ 2,461
Over three months through six months		1,669
Over six months through twelve months		2,883
Over twelve months		2,151
Total	[1]	$ 9,164	$ 9,268
[1]	Includes $2.6 billion in certificates of deposit equal to or greater than $250,000, the Federal Deposit Insurance Corporation (“FDIC”) insurance limit, as of December 31, 2020 and 2019.

Deposits (Schedule of Certifica

Deposits (Schedule of Certificates of Deposit Maturities) (Details) $ in Millions	Dec. 31, 2020USD ($)
Deposits [Abstract]
2021	$ 17,850
2022	4,520
2023	2,259
2024	1,363
2025	866
Thereafter	1,411
Total	$ 28,269

Long-Term Borrowings (Narrative

Long-Term Borrowings (Narrative) (Details) - Discover Card Master Trust I and Discover Card Execution Note Trust [Member] - Securitized Debt [Member] $ in Billions	Dec. 31, 2020USD ($)
Debt Instrument [Line Items]
Total commitment of secured credit facilities	$ 6
Total used commitment of secured credit facilities	$ 0

Long-Term Borrowings (Schedule

Long-Term Borrowings (Schedule of Long-Term Borrowings and Weighted Average Interest Rates) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Long-term borrowings		$ 21,241	$ 25,701
Variable Interest Entity, Primary Beneficiary [Member]
Debt Instrument [Line Items]
Long-term borrowings		10,840	14,284
Parent Company [Member]
Debt Instrument [Line Items]
Long-term borrowings		3,673	3,636
Securitized Debt [Member] | Discover Card Master Trust I and Discover Card Execution Note Trust [Member]
Debt Instrument [Line Items]
Long-term borrowings		$ 10,710	14,124
Securitized Debt [Member] | Discover Card Master Trust I and Discover Card Execution Note Trust [Member] | Fixed-Rate Asset-Backed Securities [Member]
Debt Instrument [Line Items]
Weighted-average interest rate	[1]	2.74%
Long-term borrowings	[1]	$ 6,041	8,609
Securitized Debt [Member] | Discover Card Master Trust I and Discover Card Execution Note Trust [Member] | Fixed-Rate Asset-Backed Securities [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate	[1]	1.85%
Securitized Debt [Member] | Discover Card Master Trust I and Discover Card Execution Note Trust [Member] | Fixed-Rate Asset-Backed Securities [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate	[1]	3.32%
Securitized Debt [Member] | Discover Card Master Trust I and Discover Card Execution Note Trust [Member] | Floating-Rate Asset-Backed Securities [Member]
Debt Instrument [Line Items]
Weighted-average interest rate	[2],[3]	0.56%
Long-term borrowings	[2],[3]	$ 4,669	5,515
Securitized Debt [Member] | Discover Card Master Trust I and Discover Card Execution Note Trust [Member] | Floating-Rate Asset-Backed Securities [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate	[2],[3]	0.39%
Securitized Debt [Member] | Discover Card Master Trust I and Discover Card Execution Note Trust [Member] | Floating-Rate Asset-Backed Securities [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate	[2],[3]	0.76%
Securitized Debt [Member] | Discover Card Master Trust I and Discover Card Execution Note Trust [Member] | Floating-Rate Asset-Backed Securities [Member] | 1-Month LIBOR [Member]
Debt Instrument [Line Items]
Interest rate terms		1-month LIBOR + 23 to 60 basis points
Securitized Debt [Member] | Discover Card Master Trust I and Discover Card Execution Note Trust [Member] | Floating-Rate Asset-Backed Securities [Member] | 1-Month LIBOR [Member] | Minimum [Member]
Debt Instrument [Line Items]
Basis spread on variable rate		0.23%
Securitized Debt [Member] | Discover Card Master Trust I and Discover Card Execution Note Trust [Member] | Floating-Rate Asset-Backed Securities [Member] | 1-Month LIBOR [Member] | Maximum [Member]
Debt Instrument [Line Items]
Basis spread on variable rate		0.60%
Securitized Debt [Member] | Student Loan Trust [Member]
Debt Instrument [Line Items]
Long-term borrowings		$ 130	160
Securitized Debt [Member] | Student Loan Trust [Member] | Floating-Rate Asset-Backed Securities [Member]
Debt Instrument [Line Items]
Weighted-average interest rate	[4],[5]	4.25%
Long-term borrowings	[4],[5]	$ 130	160
Securitized Debt [Member] | Student Loan Trust [Member] | Floating-Rate Asset-Backed Securities [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate	[4],[5]	4.25%
Securitized Debt [Member] | Student Loan Trust [Member] | Floating-Rate Asset-Backed Securities [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate		4.25%
Securitized Debt [Member] | Student Loan Trust [Member] | Floating-Rate Asset-Backed Securities [Member] | Prime Rate [Member]
Debt Instrument [Line Items]
Interest rate terms		Prime rate + 100 basis points
Basis spread on variable rate		1.00%
Securitized Debt [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Debt Instrument [Line Items]
Long-term borrowings		$ 10,840	14,284
Corporate Debt Securities [Member] | Parent Company [Member] | Fixed-Rate Senior Notes [Member]
Debt Instrument [Line Items]
Weighted-average interest rate		4.16%
Long-term borrowings		$ 3,337	3,296
Corporate Debt Securities [Member] | Parent Company [Member] | Fixed-Rate Senior Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate		3.75%
Corporate Debt Securities [Member] | Parent Company [Member] | Fixed-Rate Senior Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate		5.20%
Corporate Debt Securities [Member] | Parent Company [Member] | Fixed Rate Retail Notes [Member]
Debt Instrument [Line Items]
Weighted-average interest rate		3.73%
Long-term borrowings		$ 336	340
Corporate Debt Securities [Member] | Parent Company [Member] | Fixed Rate Retail Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate		2.85%
Corporate Debt Securities [Member] | Parent Company [Member] | Fixed Rate Retail Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate		4.60%
Senior Notes [Member] | Discover Bank [Member] | Fixed-Rate Senior Bank Notes [Member]
Debt Instrument [Line Items]
Weighted-average interest rate	[1]	3.57%
Long-term borrowings	[1]	$ 6,213	6,785
Senior Notes [Member] | Discover Bank [Member] | Fixed-Rate Senior Bank Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate	[1]	2.45%
Senior Notes [Member] | Discover Bank [Member] | Fixed-Rate Senior Bank Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate	[1]	4.65%
Subordinated Debt [Member] | Discover Bank [Member] | Fixed-Rate Subordinated Bank Notes [Member]
Debt Instrument [Line Items]
Weighted-average interest rate	[1]	4.68%
Long-term borrowings	[1]	$ 515	$ 996
Subordinated Debt [Member] | Discover Bank [Member] | Fixed-Rate Subordinated Bank Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate	[1]	4.68%
Subordinated Debt [Member] | Discover Bank [Member] | Fixed-Rate Subordinated Bank Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate	[1]	4.68%
[1]	The Company uses interest rate swaps to hedge portions of these long-term borrowings against changes in fair value attributable to changes in London Interbank Offered Rate (“LIBOR”) or Overnight Index Swap (“OIS”) Rate. Use of these interest rate swaps impacts carrying value of the debt. See Note 21: Derivatives and Hedging Activities.
[2]	Discover Card Execution Note Trust floating-rate asset-backed securities include issuances with the following interest rate terms: 1-month LIBOR + 23 to 60 basis points as of December 31, 2020.
[3]	The Company uses interest rate swaps to manage its exposure to changes in interest rates related to future cash flows resulting from interest payments on a portion of these long-term borrowings. There is no impact on debt carrying value from use of these interest rate swaps. See Note 21: Derivatives and Hedging Activities.
[4]	Repayment of this debt is dependent upon the timing of principal and interest payments on the underlying student loans. The date shown represents final maturity date.
[5]	The student loan securitization trust floating-rate asset-backed security includes an issuance with the following interest rate term: Prime rate + 100 basis points as of December 31, 2020.

Long-Term Borrowings (Schedul_2

Long-Term Borrowings (Schedule of Long-Term Borrowings Maturities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Debt Disclosure [Abstract]
2021	$ 4,217
2022	5,201
2023	3,402
2024	2,625
2025	533
Thereafter	5,263
Total	$ 21,241	$ 25,701

Stock-Based Compensation Plan_2

Stock-Based Compensation Plans (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)plansshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share-based compensation plans (in plans) | plans	2
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost | $	$ 23,000
Weighted average period of recognizing unrecognized compensation cost (in years)	10 months 2 days
Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost | $	$ 4,000
Weighted average period of recognizing unrecognized compensation cost (in years)	1 year 4 months 24 days
Award performance period (in years)	3 years
Award vesting period (in years)	3 years
Performance Stock Units [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares per performance stock unit | shares	1.5
Omnibus Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total number of shares available for grant (in shares) | shares	45,000,000
Directors Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares used in calculation of the total number of units available for grant (in shares) | shares	1,000,000
Annual awards calculation | $	$ 150
Directors Compensation Plan [Member] | Share-based Payment Arrangement, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of annual awards that shall vest (in percent)	100.00%

Stock-Based Compensation Plan_3

Stock-Based Compensation Plans (Schedule of Stock-Based Compensation Plans Compensation cost, Net of Forfeitures) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost, net of forfeitures	$ 41		$ 69	$ 81
Income tax benefit from compensation cost, net of forfeitures	9		12	15
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost, net of forfeitures	49		49	49
Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost, net of forfeitures	(8)	[1]	$ 20	$ 32
Share-based payment arrangement, plan modification, incremental cost	$ 2.4
[1]	Total PSU expense for the year ended December 31, 2020, includes an incremental $2.4 million representing a modification to the 2018 PSU award. The nature of the modification was to adjust the payout to compensate for the 2020 CECL adoption impact on EPS.

Stock-Based Compensation Plan_4

Stock-Based Compensation Plans (Schedule of Restricted Stock Unit Activity) (Details) - Restricted Stock Units [Member] - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options [Roll Forward]
Stock-based compensation, balance at beginning of period, number of units (in units)		2,148,976
Stock-based compensation, granted, number of units (in units)		631,692
Stock-based compensation, conversions to common stock, number of units (in units)		(769,525)
Stock-based compensation, forfeited, number of units (in units)		(76,744)
Stock-based compensation, balance at end of period, number of units (in units)		1,934,399	2,148,976
Stock-based compensation, vested and convertible, number of units		728,787
Stock-based compensation, weighted average remaining contractual term (in years)		9 months 29 days
Stock-based compensation, vested and convertible, weighted average remaining contractual term (in years)		0 years
Stock-based compensation, aggregate intrinsic value		$ 175	$ 182
Stock-based compensation, vested and convertible, aggregate intrinsic value		$ 66
Unvested stock-based compensation, balance at beginning of period, number of units (in units)	[1]	1,104,562
Unvested stock-based compensation, granted, number of units (in units)		631,692
Unvested stock-based compensation, vested in period, number of units (in units)		(705,427)
Unvested stock-based compensation, forfeited, number of units (in units)		(76,744)
Unvested stock-based compensation, balance at end of period, number of units (in units)	[1]	954,083	1,104,562
Unvested stock-based compensation, balance at beginning of period, weighted-average grant-date fair value	[1]	$ 72.33
Unvested stock-based compensation, granted, weighted-average grant-date fair value		76.58	$ 73.52	$ 77.53
Unvested stock-based compensation, vested in period, weighted-average grant-date fair value		72.56
Unvested stock-based compensation, forfeited, weighted-average grant-date fair value		77.19
Unvested stock-based compensation, balance at end of period, weighted-average grant-date fair value	[1]	$ 74.58	$ 72.33
[1]	Unvested RSUs represent awards where recipients have yet to satisfy either explicit vesting terms or retirement-eligibility requirements.

Stock-Based Compensation Plan_5

Stock-Based Compensation Plans (Schedule of Intrinsic Value of RSUs Converted to Common Stock and Grant Date Fair Value of RSUs Vested) (Details) - Restricted Stock Units [Member] - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of stock units converted to common stock	$ 55	$ 93	$ 67
Grant-date fair value of stock units vested	$ 51	$ 48	$ 54
Stock-based compensation, granted, weighted-average grant-date fair value	$ 76.58	$ 73.52	$ 77.53

Stock-Based Compensation Plan_6

Stock-Based Compensation Plans (Schedule of Performance Stock Unit Activity) (Details) - Performance Stock Units [Member] - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options [Roll Forward]
Stock-based compensation, balance at beginning of period, number of units (in units)	[1]	723,533
Stock-based compensation, granted, number of units (in units)		299,936
Stock-based compensation, conversions to common stock, number of units (in units)		(243,100)
Stock-based compensation, forfeited, number of units (in units)		(51,641)
Stock-based compensation, balance at end of period, number of units (in units)	[1]	728,728	[2],[3],[4]	723,533
Stock-based compensation, balance at beginning of period, weighted-average grant-date fair value	[1]	$ 73.56
Stock-based compensation, granted, weighted-average grant-date fair value		85.25		$ 71.62	$ 77.75
Stock-based compensation, conversions to common stock, weighted-average grant-date fair value		71.17
Stock-based compensation, forfeited, weighted-average grant-date fair value		75.81
Stock-based compensation, balance at end of period, weighted-average grant-date fair value	[1]	$ 79.01	[2],[3],[4]	$ 73.56
Stock-based compensation, weighted average remaining contractual term (in years)	[1],[2],[3],[4]	1 year 2 months 4 days
Stock-based compensation, aggregate intrinsic value	[1]	$ 66	[2],[3],[4]	$ 61
Performance stock units granted during period that are earned and subject to requisite service period (in units)				211,799	225,182
Performance stock units granted during period that may be earned and subject to requisite service period (in units)		291,747
[1]	All PSUs outstanding at December 31, 2020 and December 31, 2019, are unvested PSUs.
[2]	Includes 211,799 PSUs granted in 2019 that are earned based on the Company’s achievement of EPS during the three-year performance period which ends December 31, 2021, and are subject to the requisite service period which ends February 1, 2022.
[3]	Includes 225,182 PSUs granted in 2018 that are earned based on the Company’s achievement of earnings per share (“EPS”) during the three-year performance period which ends December 31, 2020, and are subject to the requisite service period which ended February 1, 2021.
[4]	Includes 291,747 PSUs granted in 2020 that may be earned based on the Company’s achievement of EPS during the three-year performance period which ends December 31, 2022, and are subject to the requisite service period which ends February 1, 2023.

Stock-Based Compensation Plan_7

Stock-Based Compensation Plans Schedule of Intrinsic Value of PSUs Converted to Common Stock and Grant Date Fair Value of PSUs Vested (Details) - Performance Stock Units [Member] - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Performance Stock Units Converted to Common Stock [Line Items]
Intrinsic value of stock units converted to common stock	$ 21	$ 33	$ 30
Grant-date fair value of stock units vested	$ 17	$ 21	$ 17
Stock-based compensation, granted, weighted-average grant-date fair value	$ 85.25	$ 71.62	$ 77.75

Employee Benefit Plans (Narrati

Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected pension plan contributions for next fiscal year	$ 0
Pretax expense associated with the 401(k) matching and fixed employer contributions	$ 99	$ 87	$ 69
Fixed Income Securities [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target asset allocations for next fiscal year (in percent)	72.00%
Defined Benefit Plan, Equity Securities [Member] | Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target asset allocations for next fiscal year (in percent)	28.00%

Employee Benefit Plans (Schedul

Employee Benefit Plans (Schedule of Net Periodic Benefit Cost) (Details) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Interest cost on projected benefit obligation	$ 21	$ 23	$ 22
Expected return on plan assets	(25)	(29)	(26)
Net amortization	7	4	5
Net periodic benefit cost (income)	$ 3	$ (2)	$ 1

Employee Benefit Plans (Sched_2

Employee Benefit Plans (Schedule of Pretax Amounts Recognized in AOCI Not Recognized as Components of Net Periodic Benefit Cost) (Details) - Pension Plans, Defined Benefit [Member] $ in Millions	Dec. 31, 2020USD ($)
Defined Benefit Plan Disclosure [Line Items]
Net loss	$ (299)
Total recognized in AOCI	$ (299)

Employee Benefit Plans (Sched_3

Employee Benefit Plans (Schedule of Funded Status and Changes in Benefit Obligations and Fair Value of Plan Assets) (Details) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of benefit obligation:
Benefit obligation at beginning of year	$ 650	$ 550
Interest cost	21	23	$ 22
Actuarial losses	98	98
Benefits paid	(21)	(21)
Benefit obligation at end of year	748	650	550
Reconciliation of fair value of plan assets:
Fair value of plan assets at beginning of year	525	455
Actual return on plan assets	110	91
Benefits paid	(21)	(21)
Fair value of plan assets at end of year	614	525	$ 455
Unfunded status (recorded in accrued expenses and other liabilities)	$ (134)	$ (125)

Employee Benefit Plans (Sched_4

Employee Benefit Plans (Schedule of Assumptions Used to Determine Benefit Obligations and Net Periodic Benefit Cost) (Details) - Pension Plans, Defined Benefit [Member]	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation discount rate (in percent)	2.47%	3.30%
Net periodic benefit cost discount rate (in percent)	3.30%	4.27%	3.68%
Net periodic benefit cost expected long-term rate of return on plan assets (in percent)	5.08%	6.15%	6.15%

Employee Benefit Plans (Sched_5

Employee Benefit Plans (Schedule of Pension Plan Assets by Level Within the Fair Value Hierarchy) (Details) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 614	$ 525	$ 455
Net asset allocation (in percent)	100.00%	100.00%
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 96	$ 94
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	373	303
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	76	67
Net Asset Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	69	61
Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	616	529
Assets [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	96	94
Assets [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	375	307
Assets [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	76	67
Assets [Member] | Net Asset Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	69	61
Assets [Member] | Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 15	$ 7
Net asset allocation (in percent)	3.00%	1.00%
Assets [Member] | Cash [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 15	$ 7
Assets [Member] | Cash [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Assets [Member] | Cash [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Assets [Member] | Cash [Member] | Net Asset Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Assets [Member] | Domestic Small/Mid Cap Equity Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 8	$ 6
Net asset allocation (in percent)	1.00%	1.00%
Assets [Member] | Domestic Small/Mid Cap Equity Fund [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0
Assets [Member] | Domestic Small/Mid Cap Equity Fund [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8	6
Assets [Member] | Domestic Small/Mid Cap Equity Fund [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Assets [Member] | Domestic Small/Mid Cap Equity Fund [Member] | Net Asset Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Assets [Member] | Emerging Markets Equity Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 20	$ 16
Net asset allocation (in percent)	3.00%	3.00%
Assets [Member] | Emerging Markets Equity Fund [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0
Assets [Member] | Emerging Markets Equity Fund [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Assets [Member] | Emerging Markets Equity Fund [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Assets [Member] | Emerging Markets Equity Fund [Member] | Net Asset Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	20	16
Assets [Member] | Global Equity Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 136	$ 121
Net asset allocation (in percent)	22.00%	23.00%
Assets [Member] | Global Equity Fund [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0
Assets [Member] | Global Equity Fund [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	83	73
Assets [Member] | Global Equity Fund [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4	3
Assets [Member] | Global Equity Fund [Member] | Net Asset Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	49	45
Assets [Member] | Domestic Large Cap Equity Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 10	$ 8
Net asset allocation (in percent)	2.00%	2.00%
Assets [Member] | Domestic Large Cap Equity Fund [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0
Assets [Member] | Domestic Large Cap Equity Fund [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10	8
Assets [Member] | Domestic Large Cap Equity Fund [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Assets [Member] | Domestic Large Cap Equity Fund [Member] | Net Asset Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Assets [Member] | Long Duration Credit Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 243	$ 205
Net asset allocation (in percent)	40.00%	39.00%
Assets [Member] | Long Duration Credit Fund [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0
Assets [Member] | Long Duration Credit Fund [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	243	205
Assets [Member] | Long Duration Credit Fund [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Assets [Member] | Long Duration Credit Fund [Member] | Net Asset Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Assets [Member] | Non-core Fixed Income Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 72	$ 64
Net asset allocation (in percent)	12.00%	12.00%
Assets [Member] | Non-core Fixed Income Fund [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0
Assets [Member] | Non-core Fixed Income Fund [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Assets [Member] | Non-core Fixed Income Fund [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	72	64
Assets [Member] | Non-core Fixed Income Fund [Member] | Net Asset Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Assets [Member] | U.S. Treasury Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 81	$ 87
Net asset allocation (in percent)	13.00%	17.00%
Assets [Member] | U.S. Treasury Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 81	$ 87
Assets [Member] | U.S. Treasury Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Assets [Member] | U.S. Treasury Securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Assets [Member] | U.S. Treasury Securities [Member] | Net Asset Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Assets [Member] | Temporary Investment Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 31	$ 15
Net asset allocation (in percent)	5.00%	3.00%
Assets [Member] | Temporary Investment Fund [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0
Assets [Member] | Temporary Investment Fund [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	31	15
Assets [Member] | Temporary Investment Fund [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Assets [Member] | Temporary Investment Fund [Member] | Net Asset Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Liabilities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(2)	(4)
Liabilities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Liabilities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2	(4)
Liabilities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Liabilities [Member] | Net Asset Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Liabilities [Member] | Futures Contracts [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ (2)	$ (4)
Net asset allocation (in percent)	1.00%	1.00%
Liabilities [Member] | Futures Contracts [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0
Liabilities [Member] | Futures Contracts [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2	(4)
Liabilities [Member] | Futures Contracts [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Liabilities [Member] | Futures Contracts [Member] | Net Asset Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0

Employee Benefit Plans (Sched_6

Employee Benefit Plans (Schedule of Expected Benefit Payments for Next Five Years and Thereafter) (Details) - Pension Plans, Defined Benefit [Member] $ in Millions	Dec. 31, 2020USD ($)
Defined Benefit Plan Disclosure [Line Items]
2021	$ 18
2022	19
2023	20
2024	22
2025	23
Following five years thereafter	$ 140

Common and Preferred Stock (Det

Common and Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Millions	Jun. 22, 2020	Oct. 31, 2017	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 19, 2021	Jul. 18, 2019
Class of Stock [Line Items]
Preferred stock, shares issued			10,700	10,700	5,700
Preferred Stock, par or stated value per share			$ 0.01	$ 0.01	$ 0.01
Net proceeds from issuance of preferred stock				$ 493	$ 0	$ 0
Preferred Stock [Member]
Class of Stock [Line Items]
Issuance of Series D preferred stock (in shares)				5,000
Preferred Stock [Member] | Series C Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares issued			5,700	5,700
Preferred Stock, par or stated value per share			$ 0.01	$ 0.01
Preferred stock, liquidation preference per share			$ 100,000	$ 100,000
Depositary shares represented by one preferred stock share			100	100
Net proceeds from issuance of preferred stock		$ 563
Redemption period of preferred stock following regulatory capital event				90 days
Preferred stock, redemption price per share			$ 100,000	$ 100,000
Preferred stock, dividend rate				5.50%
Preferred stock basis spread on variable rate				3.076%
Preferred Stock [Member] | Series C Preferred Stock [Member] | 3-Month LIBOR [Member]
Class of Stock [Line Items]
Preferred stock, dividend payment rate, variable rate to be used in future periods				three-month LIBOR
Preferred Stock [Member] | Series D Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, par or stated value per share	$ 0.01
Preferred stock, liquidation preference per share	$ 1,000
Depositary shares represented by one preferred stock share	100
Net proceeds from issuance of preferred stock	$ 493
Redemption period of preferred stock following regulatory capital event				90 days
Preferred stock, redemption price per share	$ 1,000
Preferred stock basis spread on variable rate				5.783%
Issuance of Series D preferred stock (in shares)	5,000
Preferred stock rate percentage	6.125%
Dividend rate reset	5 years
Preferred Stock [Member] | Series D Preferred Stock [Member] | Five-Year Treasury Rate [Member]
Class of Stock [Line Items]
Preferred stock, dividend payment rate, variable rate to be used in future periods				5-year Treasury
Common Stock [Member]
Class of Stock [Line Items]
Share repurchase program, authorized amount								$ 2,200
Number of shares of stock repurchased during the period (in shares)			0	4,000,000
Value of stock repurchased during the period				$ 320
Common Stock [Member] | Subsequent Event [Member]
Class of Stock [Line Items]
Share repurchase program, authorized amount							$ 1,100

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Schedule of Changes in Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax, balance at beginning of period		$ (119)
Cumulative effect of ASU No. 2018-02 adoption				$ 0
Net change in accumulated other comprehensive income (loss), net of tax		164	$ 37	25
Accumulated other comprehensive income (loss), net of tax, balance at end of period		45	(119)
Unrealized Gains (Losses) on Available-for-Sale Investment Securities, Net of Tax [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax, balance at beginning of period		112	10	(5)
Cumulative effect of ASU No. 2018-02 adoption	[1]			(1)
Net change in accumulated other comprehensive income (loss), net of tax		172	102	16
Accumulated other comprehensive income (loss), net of tax, balance at end of period		284	112	10
Gains (Losses) on Cash Flow Hedges, Net of Tax [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax, balance at beginning of period		(17)	22	10
Cumulative effect of ASU No. 2018-02 adoption	[1]			3
Net change in accumulated other comprehensive income (loss), net of tax		5	(39)	9
Accumulated other comprehensive income (loss), net of tax, balance at end of period		(12)	(17)	22
Losses on Pension Plan, Net of Tax [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax, balance at beginning of period		(214)	(188)	(157)
Cumulative effect of ASU No. 2018-02 adoption	[1]			(31)
Net change in accumulated other comprehensive income (loss), net of tax		(13)	(26)	0
Accumulated other comprehensive income (loss), net of tax, balance at end of period		(227)	(214)	(188)
AOCI [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax, balance at beginning of period		(119)	(156)	(152)
Cumulative effect of ASU No. 2018-02 adoption	[1]			(29)
Net change in accumulated other comprehensive income (loss), net of tax		164	37	25
Accumulated other comprehensive income (loss), net of tax, balance at end of period		$ 45	$ (119)	$ (156)
[1]	Represents the adjustment to AOCI as a result of adoption of ASU No. 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income, in the second quarter of 2018.

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Income (Schedule of Other Comprehensive Income Before Reclassifications and Amounts Reclassified from AOCI) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Available-for-sale investment securities, net unrealized holding gains (losses) arising during the period, before tax	$ 227	$ 135	$ 23
Available-for-sale investment securities, net unrealized holding gains (losses) arising during the period, tax benefit (expense)	(55)	(33)	(7)
Available-for-sale investment securities, net unrealized holding gains (losses) arising during the period, net of tax	172	102	16
Available-for-sale investment securities, net change, before tax	227	135	23
Available-for-sale investment securities, net change, tax benefit (expense)	(55)	(33)	(7)
Available-for-sale investment securities, net change, net of tax	172	102	16
Cash flow hedges, net unrealized gains (losses) arising during the period, before tax	(7)	(42)	17
Cash flow hedges, net unrealized gains (losses) arising during the period, tax benefit (expense)	3	7	(4)
Cash flow hedges, net unrealized gains (losses) arising during the period, net of tax	(4)	(35)	13
Cash flow hedges, amounts reclassified from AOCI, before tax	12	(5)	(6)
Cash flow hedges, amounts reclassified from AOCI, tax benefit (expense)	(3)	1	2
Cash flow hedges, amounts reclassified from AOCI, net of tax	9	(4)	(4)
Cash flow hedges, net change, before tax	5	(47)	11
Cash flow hedges, net change, tax benefit (expense)	0	8	(2)
Cash flow hedges, net change, net of tax	5	(39)	$ 9
Pension plan, unrealized gains (losses) arising during the period, before tax	(17)	(34)
Pension plan, unrealized gains (losses) arising during the period, tax benefit (expense)	4	8
Pension plan, unrealized gains (losses) arising during the period, net of tax	(13)	(26)
Pension plan, net change, before tax	(17)	(34)
Pension plan, net change, tax benefit (expense)	4	8
Pension plan, net change, net of tax	$ (13)	$ (26)

Other Expense (Schedule of Othe

Other Expense (Schedule of Other Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Component of Other Expense [Abstract]
Postage	$ 93	$ 93	$ 86
Fraud losses and other charges	96	96	83
Supplies	51	34	29
Incentive expense	57	84	85
Impairment charges	59	0	0
Other expense	240	196	186
Total other expense	$ 596	$ 503	$ 469

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Change in Income Tax Expense (Benefit), Amount	$ 584	$ (23)
Change in income tax expense, percentage	(66.50%)	2.70%
Change in effective income tax rate	(2.40%)	(0.90%)
Interest and penalties accrued for unrecognized tax benefits	$ 12	$ 14
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	$ 24

Income Taxes (Schedule of Incom

Income Taxes (Schedule of Income Tax Expense) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current tax expense, U.S. federal									$ 807	$ 836	$ 839
Current tax expense, U.S. state and local									159	175	206
Total current tax expense									966	1,011	1,045
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred tax expense, U.S. federal									(585)	(116)	(163)
Deferred tax expense, U.S. state and local									(87)	(17)	(27)
Total deferred tax expense									(672)	(133)	(190)
Income tax expense	$ 216	$ 188	$ (93)	$ (17)	$ 216	$ 224	$ 234	$ 204	$ 294	$ 878	$ 855

Income Taxes (Schedule of Recon

Income Taxes (Schedule of Reconciliation the Effective Tax Rate to the U.S. Federal Statutory Income Tax Rate) (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Reconciliation, Percent [Abstract]
United States federal statutory income tax rate	21.00%	21.00%	21.00%
United States state, local and other income taxes, net of United States federal income tax benefits	3.40%	3.50%	3.60%
Tax credits	(4.40%)	(1.40%)	(1.30%)
Other	0.50%	(0.20%)	0.50%
Effective income tax rate	20.50%	22.90%	23.80%

Income Taxes (Schedule of Defer

Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Deferred tax assets, allowance for credit losses	$ 1,997	$ 819
Deferred tax assets, compensation and benefits	84	65
Deferred tax assets, other	73	50
Total deferred tax assets before valuation allowance	2,154	934
Deferred tax assets, valuation allowance	(1)	(1)
Total deferred tax assets, net of valuation allowance	2,153	933
Deferred tax liabilities, depreciation and software amortization	(172)	(167)
Deferred tax liabilities, unrealized gains	(90)	(33)
Deferred tax liabilities, customer fees and rewards	(37)	(81)
Deferred tax liabilities, deferred loan origination costs	(21)	(28)
Deferred tax liabilities, debt exchange premium	(17)	(26)
Deferred tax liabilities, intangibles	(15)	(28)
Deferred tax liabilities, other	(26)	(19)
Total deferred tax liabilities	(378)	(382)
Net deferred tax assets	$ 1,775	$ 551

Income Taxes (Schedule of Rec_2

Income Taxes (Schedule of Reconciliation of Beginning and Ending Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, balance at beginning of period		$ 61	[1]	$ 83	[1]	$ 123
Unrecognized tax benefits, additions, current year tax positions		5		4		5
Unrecognized tax benefits, additions, prior year tax positions		3		0		6
Unrecognized tax benefits, reductions, prior year tax positions		0		(22)		(17)
Unrecognized tax benefits, reductions, settlements with taxing authorities		(2)		0		(25)
Unrecognized tax benefits, reductions, expired statute of limitations		(11)		(4)		(9)
Unrecognized tax benefits, balance at end of period	[1]	56		61		83
Unrecognized tax benefits that would favorably affect the effective tax rate		$ 51		$ 54		$ 74
[1]	For the years ended December 31, 2020, 2019 and 2018, amounts included $51 million, $54 million and $74 million, respectively, of unrecognized tax benefits, which, if recognized, would favorably affect the effective tax rate.

Earnings Per Share (Schedule of

Earnings Per Share (Schedule of Basic and Diluted EPS) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended																12 Months Ended
	Dec. 31, 2020		Sep. 30, 2020		Jun. 30, 2020		Mar. 31, 2020		Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator [Abstract]
Net income	$ 799		$ 771		$ (368)		$ (61)		$ 708		$ 770		$ 753		$ 726		$ 1,141	$ 2,957	$ 2,742
Preferred stock dividends																	(31)	(31)	(31)
Net income available to common stockholders	$ 794	[1]	$ 751	[1]	$ (369)	[1]	$ (78)	[1]	$ 704	[1]	$ 749	[1]	$ 747	[1]	$ 705	[1]	1,110	2,926	2,711
Income allocated to participating securities																	(6)	(18)	(22)
Net income allocated to common stockholders																	1,104	2,908	2,689
Net income (loss) available to common stockholders, diluted																	$ 1,104	$ 2,908	$ 2,689
Denominator [Abstract]
Weighted-average shares of common stock outstanding (in shares)																	307,000,000	320,000,000	344,000,000
Effect of dilutive common stock equivalents (in shares)																	0	0	1,000,000
Weighted-average shares of common stock outstanding and common stock equivalents (in shares)																	307,000,000	320,000,000	345,000,000
Basic earnings per common share	$ 2.59	[1]	$ 2.45	[1]	$ (1.20)	[1]	$ (0.25)	[1]	$ 2.25	[1]	$ 2.36	[1]	$ 2.32	[1]	$ 2.15	[1]	$ 3.60	$ 9.09	$ 7.81
Diluted earnings per common share	$ 2.59	[1]	$ 2.45	[1]	$ (1.20)	[1]	$ (0.25)	[1]	$ 2.25	[1]	$ 2.36	[1]	$ 2.32	[1]	$ 2.15	[1]	$ 3.60	$ 9.08	$ 7.79
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount																	0	0	0
[1]	Because the inputs to net income allocated to common stockholders and earnings per share are calculated using weighted averages for the quarter, the sum of all four quarters may differ from the year to date amounts in the consolidated statements of income.

Capital Adequacy (Narrative) (D

Capital Adequacy (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Discover Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Cash dividends paid to parent company	$ 555	$ 2,500	$ 2,400

Capital Adequacy (Schedule of M

Capital Adequacy (Schedule of Minimum and Well-Capitalized Requirements) (Details) $ in Millions		Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Parent Company [Member]
Compliance with Regulatory Capital Requirements [Line Items]
Total capital to risk-weighted assets, actual amount		$ 14,711	$ 13,250
Total capital to risk-weighted assets, actual ratio (in percent)	[1]	0.161	0.135
Total capital to risk-weighted assets, minimum capital requirements, amount		$ 7,298	$ 7,860
Total capital to risk-weighted assets, minimum capital requirements, ratio (in percent)	[2]	0.080	0.080
Total capital to risk-weighted assets, capital requirements to be classified as well-capitalized, amount	[2]	$ 9,123	$ 9,825
Total capital to risk-weighted assets, capital requirements to be classified as well-capitalized, ratio (in percent)	[2]	0.100	0.100
Tier I capital to risk-weighted assets, actual amount		$ 13,006	$ 11,595
Tier I capital to risk-weighted assets, actual ratio (in percent)	[1]	0.143	0.118
Tier I capital to risk-weighted assets, minimum capital requirements, amount		$ 5,474	$ 5,895
Tier I capital to risk-weighted assets, minimum capital requirements, ratio (in percent)	[2]	0.060	0.060
Tier I capital to risk-weighted assets, capital requirements to be classified as well-capitalized, amount	[2]	$ 5,474	$ 5,895
Tier I capital to risk-weighted assets, capital requirements to be classified as well-capitalized, ratio (in percent)	[2]	0.060	0.060
Tier I capital to average assets, actual amount		$ 13,006	$ 11,595
Tier I capital to average assets, actual ratio (in percent)	[1]	0.109	0.103
Tier I capital to average assets, minimum capital requirements, amount		$ 4,757	$ 4,482
Tier I capital to average assets, minimum capital requirements, ratio (in percent)	[2]	0.040	0.040
CET1 capital to risk-weighted assets, actual amount		$ 11,950	$ 11,032
CET1 capital to risk-weighted assets, actual ratio (in percent)	[1]	0.131	0.112
CET1 capital to risk-weighted assets, minimum capital requirements, amount		$ 4,105	$ 4,421
CET1 capital to risk-weighted assets, minimum capital requirements, ratio (in percent)	[2]	4.50%	4.50%
Discover Bank [Member]
Compliance with Regulatory Capital Requirements [Line Items]
Total capital to risk-weighted assets, actual amount		$ 14,507	$ 13,441
Total capital to risk-weighted assets, actual ratio (in percent)	[1]	0.161	0.138
Total capital to risk-weighted assets, minimum capital requirements, amount		$ 7,214	$ 7,776
Total capital to risk-weighted assets, minimum capital requirements, ratio (in percent)		0.080	0.080
Total capital to risk-weighted assets, capital requirements to be classified as well-capitalized, amount		$ 9,018	$ 9,720
Total capital to risk-weighted assets, capital requirements to be classified as well-capitalized, ratio (in percent)		0.100	0.100
Tier I capital to risk-weighted assets, actual amount		$ 12,415	$ 11,203
Tier I capital to risk-weighted assets, actual ratio (in percent)	[1]	0.138	0.115
Tier I capital to risk-weighted assets, minimum capital requirements, amount		$ 5,411	$ 5,832
Tier I capital to risk-weighted assets, minimum capital requirements, ratio (in percent)		0.060	0.060
Tier I capital to risk-weighted assets, capital requirements to be classified as well-capitalized, amount		$ 7,214	$ 7,776
Tier I capital to risk-weighted assets, capital requirements to be classified as well-capitalized, ratio (in percent)		0.080	0.080
Tier I capital to average assets, actual amount		$ 12,415	$ 11,203
Tier I capital to average assets, actual ratio (in percent)	[1]	0.105	0.101
Tier I capital to average assets, minimum capital requirements, amount		$ 4,709	$ 4,435
Tier I capital to average assets, minimum capital requirements, ratio (in percent)		0.040	0.040
Tier I capital to average assets, capital requirements to be classified as well-capitalize, amount		$ 5,886	$ 5,544
Tier I capital to average assets, capital requirements to be classified as well-capitalized, ratio (in percent)		0.050	0.050
CET1 capital to risk-weighted assets, actual amount		$ 12,415	$ 11,203
CET1 capital to risk-weighted assets, actual ratio (in percent)	[1]	0.138	0.115
CET1 capital to risk-weighted assets, minimum capital requirements, amount		$ 4,058	$ 4,374
CET1 capital to risk-weighted assets, minimum capital requirements, ratio (in percent)		4.50%	4.50%
CET1 capital to risk-weighted assets, capital requirements to be classified as well-capitalized, amount		$ 5,862	$ 6,318
CET1 capital to risk-weighted assets, capital requirements to be classified as well-capitalized, ratio (in percent)		6.50%	6.50%
[1]	Capital ratios are calculated based on the Basel III Standardized Approach rules, subject to applicable transition provisions, including CECL transition provisions.
[2]	The Basel III rules do not establish well-capitalized thresholds for these measures for bank holding companies. Existing well-capitalized thresholds established in the Federal Reserve’s Regulation Y have been included where available.

Commitments, Contingencies an_3

Commitments, Contingencies and Guarantees (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Commitments, Contingencies and Guarantees [Line Items]
Off-Balance sheet, credit loss, liability	$ 0
Maximum potential counterparty exposure	60
Contingent liabilities related to equity method investments	0
Escrow deposits and settlement withholdings	16	$ 8
Commitments to Extend Credit [Member]
Commitments, Contingencies and Guarantees [Line Items]
Unused commitments to extend credit for loans	$ 213,700

Commitments, Contingencies an_4

Commitments, Contingencies and Guarantees (Schedule of Maximum Potential Counterparty Exposures Related to Settlement Guarantees and Merchant Chargeback Guarantee) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Merchant Chargeback Guarantees [Member]
Loss Contingencies [Line Items]
Aggregate sales transaction volume	[1]	$ 175,026	$ 172,463	$ 158,910
[1]	Represents transactions processed on the Discover Network for which a potential liability exists that, in aggregate, can differ from credit card sales volume.

Litigation and Regulatory Mat_2

Litigation and Regulatory Matters (Details) - USD ($) $ in Millions	Dec. 22, 2020	Dec. 31, 2020
Loss Contingencies [Line Items]
Litigation Settlement, Expense		$ 31
Unfavorable Regulatory Action [Member] | Consumer Financial Protection Bureau Consent Order [Member]
Loss Contingencies [Line Items]
Amount of civil money penalty for CFPB consent order	$ 25
Maximum [Member] | Pending and Threatened Litigation [Member]
Loss Contingencies [Line Items]
Aggregate range of reasonably possible losses		$ 220
Minimum [Member] | Unfavorable Regulatory Action [Member] | Consumer Financial Protection Bureau Consent Order [Member]
Loss Contingencies [Line Items]
Aggregate range of reasonably possible losses	$ 10

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of intangible assets, indefinite-lived (excluding goodwill)	$ 59,000,000
Goodwill and Intangible Asset Impairment		$ 0
Residential Mortgage Backed Securities - Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale security, par value	$ 286,000,000
Available for sale securities, weighted average coupon rate (in percent)	2.77%
Available for sale securities, weighted average remaining maturity (in years)	3 years

Fair Value Measurements (Schedu

Fair Value Measurements (Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions		Dec. 31, 2020		Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	[1]	$ 9,654		$ 10,323
U.S. Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	[1]	9,354		9,906
Residential Mortgage Backed Securities - Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale	[1]	300	[2]	417
Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		9,654		10,323
Fair Value, Recurring [Member] | Interest Rate Swaps [Member] | Cash Flow Hedges [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, liabilities, fair value	[3]			2
Fair Value, Recurring [Member] | Interest Rate Swaps [Member] | Fair Value Hedges [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets, fair value	[3]	1
Derivative financial instruments, liabilities, fair value	[3]			4
Fair Value, Recurring [Member] | Foreign Exchange Forward Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, liabilities, fair value	[3]			1
Fair Value, Recurring [Member] | U.S. Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		9,354		9,906
Fair Value, Recurring [Member] | Residential Mortgage Backed Securities - Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		300		417
Fair Value, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		9,354		9,906
Fair Value, Recurring [Member] | Level 1 [Member] | Interest Rate Swaps [Member] | Cash Flow Hedges [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, liabilities, fair value	[3]			0
Fair Value, Recurring [Member] | Level 1 [Member] | Interest Rate Swaps [Member] | Fair Value Hedges [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets, fair value	[3]	0
Derivative financial instruments, liabilities, fair value	[3]			0
Fair Value, Recurring [Member] | Level 1 [Member] | Foreign Exchange Forward Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, liabilities, fair value	[3]			0
Fair Value, Recurring [Member] | Level 1 [Member] | U.S. Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		9,354		9,906
Fair Value, Recurring [Member] | Level 1 [Member] | Residential Mortgage Backed Securities - Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		0		0
Fair Value, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		300		417
Fair Value, Recurring [Member] | Level 2 [Member] | Interest Rate Swaps [Member] | Cash Flow Hedges [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, liabilities, fair value	[3]			2
Fair Value, Recurring [Member] | Level 2 [Member] | Interest Rate Swaps [Member] | Fair Value Hedges [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets, fair value	[3]	1
Derivative financial instruments, liabilities, fair value	[3]			4
Fair Value, Recurring [Member] | Level 2 [Member] | Foreign Exchange Forward Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, liabilities, fair value	[3]			1
Fair Value, Recurring [Member] | Level 2 [Member] | U.S. Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		0		0
Fair Value, Recurring [Member] | Level 2 [Member] | Residential Mortgage Backed Securities - Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		300		417
Fair Value, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		0		0
Fair Value, Recurring [Member] | Level 3 [Member] | Interest Rate Swaps [Member] | Cash Flow Hedges [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, liabilities, fair value	[3]			0
Fair Value, Recurring [Member] | Level 3 [Member] | Interest Rate Swaps [Member] | Fair Value Hedges [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets, fair value	[3]	0
Derivative financial instruments, liabilities, fair value	[3]			0
Fair Value, Recurring [Member] | Level 3 [Member] | Foreign Exchange Forward Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, liabilities, fair value	[3]			0
Fair Value, Recurring [Member] | Level 3 [Member] | U.S. Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		0		0
Fair Value, Recurring [Member] | Level 3 [Member] | Residential Mortgage Backed Securities - Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale		$ 0		$ 0
[1]	Available-for-sale investment securities are reported at fair value.
[2]	Maturities of residential mortgage-backed securities are reflective of the contractual maturities of the investment.
[3]	Derivative instrument carrying values in an asset or liability position are presented as part of other assets or accrued expenses and other liabilities, respectively, in the Company’s consolidated statements of financial condition.

Fair Value Measurements (Sche_2

Fair Value Measurements (Schedule of Financial Instruments Measured at Other Than Fair Value) (Details) - USD ($) $ in Millions		Dec. 31, 2020		Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities	[1]	$ 269		$ 274
Fair Value, Nonrecurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Short-term Investments Fair Value Disclosure		2,200
Residential Mortgage Backed Securities - Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities	[1],[2]	269	[3]	274
Level 1 [Member] | Fair Value, Nonrecurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Short-term Investments Fair Value Disclosure		2,200
Level 2 [Member] | Fair Value, Nonrecurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Short-term Investments Fair Value Disclosure		0
Level 3 [Member] | Fair Value, Nonrecurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Short-term Investments Fair Value Disclosure		0
Estimate of Fair Value Measurement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities		269		274
Net loan receivables		91,200		96,094
Cash and cash equivalents	[4]	13,564		6,924
Restricted cash	[4]	25		40
Accrued interest receivables	[4],[5]	992		1,044
Time deposits	[6]	29,090		34,910
Long-term borrowings		22,342		26,572
Accrued interest payables	[4],[5]	233		283
Estimate of Fair Value Measurement | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term borrowings		10,924		14,383
Estimate of Fair Value Measurement | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term borrowings		11,418		12,189
Estimate of Fair Value Measurement | Residential Mortgage Backed Securities - Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities		269		274
Estimate of Fair Value Measurement | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities		0		0
Net loan receivables		0		0
Cash and cash equivalents	[4]	13,564		6,924
Restricted cash	[4]	25		40
Accrued interest receivables	[4],[5]	0		0
Time deposits	[6]	0		0
Long-term borrowings		0		0
Accrued interest payables	[4],[5]	0		0
Estimate of Fair Value Measurement | Level 1 [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term borrowings		0		0
Estimate of Fair Value Measurement | Level 1 [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term borrowings		0		0
Estimate of Fair Value Measurement | Level 1 [Member] | Residential Mortgage Backed Securities - Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities		0		0
Estimate of Fair Value Measurement | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities		269		274
Net loan receivables		0		0
Cash and cash equivalents	[4]	0		0
Restricted cash	[4]	0		0
Accrued interest receivables	[4],[5]	992		1,044
Time deposits	[6]	29,090		34,910
Long-term borrowings		22,212		26,400
Accrued interest payables	[4],[5]	233		283
Estimate of Fair Value Measurement | Level 2 [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term borrowings		10,794		14,211
Estimate of Fair Value Measurement | Level 2 [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term borrowings		11,418		12,189
Estimate of Fair Value Measurement | Level 2 [Member] | Residential Mortgage Backed Securities - Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities		269		274
Estimate of Fair Value Measurement | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities		0		0
Net loan receivables		91,200		96,094
Cash and cash equivalents	[4]	0		0
Restricted cash	[4]	0		0
Accrued interest receivables	[4],[5]	0		0
Time deposits	[6]	0		0
Long-term borrowings		130		172
Accrued interest payables	[4],[5]	0		0
Estimate of Fair Value Measurement | Level 3 [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term borrowings		130		172
Estimate of Fair Value Measurement | Level 3 [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term borrowings		0		0
Estimate of Fair Value Measurement | Level 3 [Member] | Residential Mortgage Backed Securities - Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities		0		0
Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities		260		272
Net loan receivables		82,223		92,511
Cash and cash equivalents	[4]	13,564		6,924
Restricted cash	[4]	25		40
Accrued interest receivables	[4],[5]	992		1,044
Time deposits	[6]	28,269		34,381
Long-term borrowings		21,241		25,701
Accrued interest payables	[4],[5]	233		283
Carrying Value [Member] | Fair Value, Nonrecurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other Short-term Investments Fair Value Disclosure		2,200
Carrying Value [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term borrowings		10,840		14,284
Carrying Value [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term borrowings		10,401		11,417
Carrying Value [Member] | Residential Mortgage Backed Securities - Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities		$ 260		$ 272
[1]	Held-to-maturity investment securities are reported at amortized cost.
[2]	Amounts represent residential mortgage-backed securities that were classified as held-to-maturity as they were entered into as a part of the Company’s community reinvestment initiatives.
[3]	Maturities of residential mortgage-backed securities are reflective of the contractual maturities of the investment.
[4]	The carrying values of these assets and liabilities approximate fair value due to their short-term nature.
[5]	Accrued interest receivable and payable carrying values are presented as part of other assets or accrued expenses and other liabilities, respectively, in the Company’s consolidated statements of financial condition.
[6]	Excludes deposits without contractually defined maturities for all periods presented.

Derivatives and Hedging Activ_3

Derivatives and Hedging Activities (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)transactions
Discover Bank [Member]
Derivative [Line Items]
Additional collateral	$ 0
Parent Company [Member]
Derivative [Line Items]
Additional collateral	$ 0
Derivative, Number of Instruments Held | transactions	0
Interest Expense [Member]
Derivative [Line Items]
Cash flow hedge loss to be reclassified to earnings within twelve months	$ 3
Financing Receivable [Member]
Derivative [Line Items]
Initial maximum period for cash flow hedges (in years)	2 years

Derivatives and Hedging Activ_4

Derivatives and Hedging Activities (Schedule of Fair Value and Outstanding Notional Amounts of Derivative Instruments and Related Collateral Balances) (Details) € in Millions, ₨ in Millions, £ in Millions, $ in Millions, $ in Millions		Dec. 31, 2020USD ($)transactions		Dec. 31, 2020EUR (€)transactions	Dec. 31, 2020GBP (£)transactions	Dec. 31, 2020SGD ($)transactions	Dec. 31, 2020INR (₨)transactions	Dec. 31, 2019USD ($)transactions		Dec. 31, 2019EUR (€)transactions	Dec. 31, 2019GBP (£)transactions	Dec. 31, 2019SGD ($)transactions	Dec. 31, 2019INR (₨)transactions
Derivatives, Fair Value [Line Items]
Derivative assets	[1]	$ 1						$ 0
Collateral held, derivative assets	[2]	0						0
Total net derivative assets		1						0
Derivative liabilities	[1]	0						7
Collateral posted, derivative liabilities	[2]	0						(7)
Total net derivative liabilities		0						0
Designated as Hedges [Member] | Cash Flow Hedges [Member] | Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative, notional amount		$ 250						900
Derivative, number of outstanding derivative contracts | transactions		1		1	1	1	1
Derivative assets		$ 0						0
Derivative liabilities		0						2
Designated as Hedges [Member] | Fair Value Hedges [Member] | Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative, notional amount		$ 11,625						14,275
Derivative, number of outstanding derivative contracts | transactions		15		15	15	15	15
Derivative assets		$ 1						0
Derivative liabilities		0						4
Not Designated as Hedges [Member] | Foreign Exchange Forward Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative, notional amount		$ 24	[3]	€ 6	£ 6	$ 1	₨ 596	38	[3]	€ 9	£ 14	$ 1	₨ 596
Derivative, number of outstanding derivative contracts | transactions		6		6	6	6	6
Derivative assets		$ 0						0
Derivative liabilities		0						1
Not Designated as Hedges [Member] | When-Issued Mortgage-Backed Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative, notional amount		$ 27						$ 42
Derivative, number of outstanding derivative contracts | transactions		1		1	1	1	1	2		2	2	2	2
[1]	In addition to the derivatives disclosed in the table, the Company enters into forward contracts to purchase when-issued mortgage-backed securities as part of its community reinvestment initiatives. At December 31, 2020, the Company had one outstanding contract with a total notional amount of $27 million and immaterial fair value. At December 31, 2019, the Company had two outstanding contracts with a total notional amount of $42 million and immaterial fair value.
[2]	Collateral amounts, which consist of both cash and investment securities, are limited to the related derivative asset/liability balance and do not include excess collateral received/pledged
[3]	The foreign exchange forward contracts have notional amounts of EUR 6 million, GBP 6 million, SGD 1 million and INR 596 million as of December 31, 2020, and notional amounts of EUR 9 million, GBP 14 million, SGD 1 million and INR 596 million as of December 31, 2019.

Derivatives and Hedging Activ_5

Derivatives and Hedging Activities Derivatives and Hedging Activities (Schedule of Hedged Items in Fair Value Hedging Relationship) (Details) - Long-term Borrowings [Member] - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Schedule of Hedged Items in Fair Value Hedging Relationship [Line Items]
Carrying amount of hedged assets/liabilities	$ 11,881	$ 14,244
Cumulative amount of fair value hedging adjustment increasing (decreasing) the carrying amount of hedged assets/liabilities	$ 281	$ 13

Derivatives and Hedging Activ_6

Derivatives and Hedging Activities (Schedule of Impact of the Derivative Instruments on Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Amounts reclassified from OCI into earnings, cash flow hedges	$ (12)	$ 5	$ 6
Interest Expense [Member] | Deposits [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total amounts of income and expense line items presented in the statements of income in which the effects of fair value or cash flow hedges are recorded			(1,238)
Interest Expense [Member] | Deposits [Member] | Designated as Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total amounts of income and expense line items presented in the statements of income in which the effects of fair value or cash flow hedges are recorded	(1,231)	(1,587)
Interest Expense [Member] | Deposits [Member] | Designated as Hedges [Member] | Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amounts reclassified from OCI into earnings, cash flow hedges	(9)	3	0
Gains (losss) on hedged items, fair value hedges	0	0	0
Gains (losses) on interest rate swap, fair value hedges	0	0	0
Total gains (losses) on fair value hedges	0	0	0
Interest Expense [Member] | Deposits [Member] | Not Designated as Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as hedges		0	0
Interest Expense [Member] | Long-term Borrowings [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total amounts of income and expense line items presented in the statements of income in which the effects of fair value or cash flow hedges are recorded			(901)
Interest Expense [Member] | Long-term Borrowings [Member] | Designated as Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total amounts of income and expense line items presented in the statements of income in which the effects of fair value or cash flow hedges are recorded	(602)	(943)
Interest Expense [Member] | Long-term Borrowings [Member] | Designated as Hedges [Member] | Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amounts reclassified from OCI into earnings, cash flow hedges	(3)	2	6
Gains (losss) on hedged items, fair value hedges	(268)	(104)	(18)
Gains (losses) on interest rate swap, fair value hedges	423	72	(23)
Total gains (losses) on fair value hedges	155	(32)	(41)
Interest Expense [Member] | Long-term Borrowings [Member] | Not Designated as Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as hedges		0	0
Other Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total amounts of income and expense line items presented in the statements of income in which the effects of fair value or cash flow hedges are recorded			97
Other Income [Member] | Designated as Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total amounts of income and expense line items presented in the statements of income in which the effects of fair value or cash flow hedges are recorded	56	93
Other Income [Member] | Designated as Hedges [Member] | Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amounts reclassified from OCI into earnings, cash flow hedges	0	0	0
Gains (losss) on hedged items, fair value hedges	0	0	0
Gains (losses) on interest rate swap, fair value hedges	0	0	0
Total gains (losses) on fair value hedges	$ 0	0	0
Other Income [Member] | Not Designated as Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivatives not designated as hedges		$ (1)	$ 1

Segment Disclosures (Narrative)

Segment Disclosures (Narrative) (Details)	12 Months Ended
	Dec. 31, 2020segment
Segment Reporting [Abstract]
Number of reportable segments	2

Segment Disclosures (Schedule o

Segment Disclosures (Schedule of Segment Disclosures) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Segment Reporting Information [Line Items]
Interest income	$ 2,760	$ 2,681	$ 2,672	$ 2,982	$ 3,039	$ 3,040	$ 2,977	$ 2,937	$ 11,095		$ 11,993		$ 10,893
Interest expense	383	416	482	584	615	638	645	632	1,865		2,530		2,139
Net interest income	2,377	2,265	2,190	2,398	2,424	2,402	2,332	2,305	9,230		9,463		8,754
Provision for credit losses	531	750	2,046	1,807	836	799	787	809	5,134	[1],[2]	3,231	[1],[2],[3]	3,035	[1],[2],[3]
Other income	447	449	472	490	520	498	520	458	1,858		1,996		1,955
Other expense	1,278	1,005	1,077	1,159	1,184	1,107	1,078	1,024	4,519		4,393		4,077
Income before income tax benefit and equity in undistributed net income of subsidiaries	$ 1,015	$ 959	$ (461)	$ (78)	$ 924	$ 994	$ 987	$ 930	1,435		3,835		3,597
Other [Member]
Segment Reporting Information [Line Items]
Interest income													370
Credit Card Loans [Member]
Segment Reporting Information [Line Items]
Interest income									8,985		9,690		8,835
Total Other Loans [Member] | Personal Loans [Member]
Segment Reporting Information [Line Items]
Interest income									958		983		935
Total Other Loans [Member] | Other [Member]
Segment Reporting Information [Line Items]
Interest income									398		503
Total Other Loans [Member] | Private Student Loans [Member]
Segment Reporting Information [Line Items]
Interest income									754		817		753
Operating Segments [Member] | Digital Banking [Member]
Segment Reporting Information [Line Items]
Interest income									11,095		11,992		10,892
Interest expense									1,865		2,530		2,139
Net interest income									9,230		9,462		8,753
Provision for credit losses									5,134		3,233	[3]	3,035	[3]
Other income									1,459		1,648		1,645
Other expense									4,292		4,231		3,918
Income before income tax benefit and equity in undistributed net income of subsidiaries									1,263		3,646		3,445
Operating Segments [Member] | Digital Banking [Member] | Other [Member]
Segment Reporting Information [Line Items]
Interest income													369
Operating Segments [Member] | Digital Banking [Member] | Credit Card Loans [Member]
Segment Reporting Information [Line Items]
Interest income									8,985		9,690		8,835
Operating Segments [Member] | Digital Banking [Member] | Total Other Loans [Member] | Personal Loans [Member]
Segment Reporting Information [Line Items]
Interest income									958		983		935
Operating Segments [Member] | Digital Banking [Member] | Total Other Loans [Member] | Other [Member]
Segment Reporting Information [Line Items]
Interest income									398		502
Operating Segments [Member] | Digital Banking [Member] | Total Other Loans [Member] | Private Student Loans [Member]
Segment Reporting Information [Line Items]
Interest income									754		817		753
Operating Segments [Member] | Payment Services [Member]
Segment Reporting Information [Line Items]
Interest income									0		1		1
Interest expense									0		0		0
Net interest income									0		1		1
Provision for credit losses									0		(2)	[3]	0	[3]
Other income									399		348		310
Other expense									227		162		159
Income before income tax benefit and equity in undistributed net income of subsidiaries									172		189		152
Operating Segments [Member] | Payment Services [Member] | Other [Member]
Segment Reporting Information [Line Items]
Interest income													1
Operating Segments [Member] | Payment Services [Member] | Credit Card Loans [Member]
Segment Reporting Information [Line Items]
Interest income									0		0		0
Operating Segments [Member] | Payment Services [Member] | Total Other Loans [Member] | Personal Loans [Member]
Segment Reporting Information [Line Items]
Interest income									0		0		0
Operating Segments [Member] | Payment Services [Member] | Total Other Loans [Member] | Other [Member]
Segment Reporting Information [Line Items]
Interest income									0		1
Operating Segments [Member] | Payment Services [Member] | Total Other Loans [Member] | Private Student Loans [Member]
Segment Reporting Information [Line Items]
Interest income									$ 0		$ 0		$ 0
[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 ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach.
[3]	Prior to the adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach

Revenue from Contracts with C_3

Revenue from Contracts with Customers (Schedule of Revenue from Contracts with Customers Disaggregated by Business Segment) (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Discount and interchange revenue, net										$ 933	$ 1,066	$ 1,074
Protection products revenue										180	194	204
Transaction processing revenue										195	197	178
Other income subject to ASC 606										56	93	97
Loan fee income										414	449	402
Other income not subject to ASC 606										80	(3)
Total other income not subject to ASC 606										494	446	402
Total other income		$ 447	$ 449	$ 472	$ 490	$ 520	$ 498	$ 520	$ 458	1,858	1,996	1,955
Customer rewards included in discount and interchange revenue										1,900	1,900	1,800
Deposit product fees reported in net interest income and excluded from other income subject to ASC 606										2	3	3
Accounting Standards Update 2014-09 [Member]
Disaggregation of Revenue [Line Items]
Discount and interchange revenue, net	[1]									933	1,066	1,074
Protection products revenue										180	194	204
Transaction processing revenue										195	197	178
Other income subject to ASC 606										56	93	97
Total other income subject to ASC 606	[2]									1,364	1,550	1,553
Operating Segments [Member] | Digital Banking [Member]
Disaggregation of Revenue [Line Items]
Loan fee income										414	449	402
Other income not subject to ASC 606										1	(3)
Total other income not subject to ASC 606										415	446	402
Total other income										1,459	1,648	1,645
Operating Segments [Member] | Digital Banking [Member] | Accounting Standards Update 2014-09 [Member]
Disaggregation of Revenue [Line Items]
Discount and interchange revenue, net	[1]									871	1,000	1,022
Protection products revenue										180	194	204
Transaction processing revenue										0	0	0
Other income subject to ASC 606										(7)	8	17
Total other income subject to ASC 606	[2]									1,044	1,202	1,243
Operating Segments [Member] | Payment Services [Member]
Disaggregation of Revenue [Line Items]
Loan fee income										0	0	0
Other income not subject to ASC 606										79	0
Total other income not subject to ASC 606										79	0	0
Total other income										399	348	310
Operating Segments [Member] | Payment Services [Member] | Accounting Standards Update 2014-09 [Member]
Disaggregation of Revenue [Line Items]
Discount and interchange revenue, net	[1]									62	66	52
Protection products revenue										0	0	0
Transaction processing revenue										195	197	178
Other income subject to ASC 606										63	85	80
Total other income subject to ASC 606	[2]									$ 320	$ 348	$ 310
[1]	Net of rewards, including Cashback Bonus rewards, of $1.9 billion, $1.9 billion and $1.8 billion for the years ended December 31, 2020, 2019 and 2018, respectively.
[2]	Excludes $2 million, $3 million and $3 million deposit product fees that are reported within net interest income for the years ended December 31, 2020, 2019 and 2018, respectively.

Parent Company Condensed Fina_3

Parent Company Condensed Financial Information (Schedule of Parent Company Condensed Statements of Financial Condition) (Details) - USD ($) $ in Millions		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Assets
Cash and cash equivalents		$ 13,564		$ 6,924		$ 13,299
Restricted cash		25		40		1,846
Other assets		3,586		2,459
Total assets		112,889		113,996
Liabilities and Stockholders’ Equity
Non-interest bearing deposit accounts		1,209		791
Long-term borrowings		21,241		25,701
Accrued expenses and other liabilities		3,860		3,690
Total liabilities		102,005		102,137
Stockholders’ equity		10,884		11,859		11,130	$ 10,892
Total liabilities and stockholders’ equity		112,889		113,996
Parent Company [Member]
Assets
Cash and cash equivalents		2,802	[1]	2,511	[1]	1,586
Restricted cash		20		20		$ 20
Notes receivable from subsidiaries	[2]	891		877
Investments in bank subsidiaries		10,188		11,319
Investments in non-bank subsidiaries		727		820
Other assets		567		600
Total assets		15,195		16,147
Liabilities and Stockholders’ Equity
Non-interest bearing deposit accounts		2		2
Short-term borrowings from subsidiaries		283		283
Long-term borrowings		3,673		3,636
Accrued expenses and other liabilities		353		367
Total liabilities		4,311		4,288
Stockholders’ equity		10,884		11,859
Total liabilities and stockholders’ equity		15,195		16,147
Parent Company [Member] | Discover Bank [Member]
Liabilities and Stockholders’ Equity
Liquidity available to parent from money market deposit account at subsidiary		2,700		2,400
Liquidity available to parent from funds advanced to subsidiary		$ 500		$ 500
[1]	The Parent Company had $2.7 billion and $2.4 billion in a money market deposit account at Discover Bank as of December 31, 2020 and 2019, respectively, which is included in cash and cash equivalents. These funds are available to the Parent for liquidity purposes.
[2]	The Parent Company advanced $500 million to Discover Bank as of December 31, 2020 and 2019, which is included in notes receivable from subsidiaries. These funds are available to the Parent for liquidity purposes.

Parent Company Condensed Fina_4

Parent Company Condensed Financial Information (Schedule of Parent Company Condensed Statements of Income) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Financial Statements, Captions [Line Items]
Interest income	$ 2,760	$ 2,681	$ 2,672	$ 2,982	$ 3,039	$ 3,040	$ 2,977	$ 2,937	$ 11,095	$ 11,993	$ 10,893
Interest expense	383	416	482	584	615	638	645	632	1,865	2,530	2,139
Net interest expense	2,377	2,265	2,190	2,398	2,424	2,402	2,332	2,305	9,230	9,463	8,754
Other expense	1,278	1,005	1,077	1,159	1,184	1,107	1,078	1,024	4,519	4,393	4,077
Income before income tax benefit and equity in undistributed net income of subsidiaries	1,015	959	(461)	(78)	924	994	987	930	1,435	3,835	3,597
Income tax benefit	(216)	(188)	93	17	(216)	(224)	(234)	(204)	(294)	(878)	(855)
Net income	$ 799	$ 771	$ (368)	$ (61)	$ 708	$ 770	$ 753	$ 726	1,141	2,957	2,742
Other comprehensive income, net									164	37	25
Comprehensive income									1,305	2,994	2,767
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Interest income									44	82	67
Interest expense									205	212	189
Net interest expense									(161)	(130)	(122)
Dividends from bank subsidiaries									555	2,530	2,375
Dividends from non-bank subsidiaries									200	100	450
Total income									594	2,500	2,703
Other expense									(16)	1	0
Income before income tax benefit and equity in undistributed net income of subsidiaries									610	2,499	2,703
Income tax benefit									30	25	33
Equity in undistributed net income of subsidiaries									501	433	6
Net income									1,141	2,957	2,742
Other comprehensive income, net									164	37	25
Comprehensive income									$ 1,305	$ 2,994	$ 2,767

Parent Company Condensed Fina_5

Parent Company Condensed Financial Information (Schedule of Parent Company Condensed Statements of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended										12 Months Ended
	Dec. 31, 2020		Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019		Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Cash flows provided by operating activities
Net income	$ 799		$ 771	$ (368)	$ (61)	$ 708		$ 770	$ 753	$ 726	$ 1,141		$ 2,957		$ 2,742
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred income taxes											(672)		(133)		(190)
Depreciation and amortization											98		84		75
Changes in assets and liabilities:
Decrease (increase) in other assets											118		(202)		(7)
Net cash provided by operating activities											6,196		6,196		5,191
Cash flows provided by (used for) investing activities
Net cash used for investing activities											1,514		(15,274)		(10,579)
Cash flows (used for) provided by financing activities
Proceeds from issuance of common stock											10		7		6
Maturities and repayment of long-term borrowings											(1,755)		(286)		(1,756)
Purchases of treasury stock											(348)		(1,768)		(2,065)
Net increase (decrease) in deposits											4,128		4,945		8,961
Proceeds from issuance of preferred stock											493		0		0
Dividends paid on common and preferred stock											(576)		(573)		(552)
Net cash used for financing activities											(1,085)		897		7,146
Increase (decrease) in cash, cash equivalents and restricted cash											6,625		(8,181)		1,758
Cash, cash equivalents and restricted cash, at beginning of period					6,964					15,145	6,964		15,145		13,387
Cash, cash equivalents and restricted cash, at end of period	13,589					6,964					13,589		6,964		15,145
Reconciliation of cash, cash equivalents and restricted cash
Cash and cash equivalents	13,564					6,924					13,564		6,924		13,299
Restricted cash	25					40					25		40		1,846
Cash paid during the period for
Interest expense											1,799		2,407		1,847
Income taxes, net of income tax refunds											901		1,088		650
Parent Company [Member]
Cash flows provided by operating activities
Net income											1,141		2,957		2,742
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed net income of subsidiaries											(501)		(433)		(6)
Stock-based compensation expense											42		69		81
Deferred income taxes											(5)		(8)		(5)
Depreciation and amortization											41		38		34
Changes in assets and liabilities:
Decrease (increase) in other assets											42		92		(416)
(Decrease) increase in other liabilities and accrued expenses											(30)		50		(129)
Net cash provided by operating activities											730		2,765		2,301
Cash flows provided by (used for) investing activities
Decrease (increase) in investment in subsidiaries											0		0		(3)
Increase in loans to subsidiaries											(15)		(55)		(62)
Net cash used for investing activities											(15)		(55)		(65)
Cash flows (used for) provided by financing activities
Net increase (decrease) in short-term borrowings from subsidiaries											0		42		(110)
Proceeds from issuance of common stock											10		7		6
Proceeds from issuance of long-term borrowings											0		595		49
Maturities and repayment of long-term borrowings											(3)		(86)		(6)
Purchases of treasury stock											(348)		(1,768)		(2,065)
Net increase (decrease) in deposits											0		(2)		1
Proceeds from issuance of preferred stock											493		0		0
Dividends paid on common and preferred stock											(576)		(573)		(552)
Net cash used for financing activities											(424)		(1,785)		(2,677)
Increase (decrease) in cash, cash equivalents and restricted cash											291		925		(441)
Cash, cash equivalents and restricted cash, at beginning of period					$ 2,531					$ 1,606	2,531		1,606		2,047
Cash, cash equivalents and restricted cash, at end of period	2,822					2,531					2,822		2,531		1,606
Reconciliation of cash, cash equivalents and restricted cash
Cash and cash equivalents	2,802	[1]				2,511	[1]				2,802	[1]	2,511	[1]	1,586
Restricted cash	$ 20					$ 20					20		20		20
Cash paid during the period for
Interest expense											168		170		156
Income taxes, net of income tax refunds											$ (31)		$ 20		$ (22)
[1]	The Parent Company had $2.7 billion and $2.4 billion in a money market deposit account at Discover Bank as of December 31, 2020 and 2019, respectively, which is included in cash and cash equivalents. These funds are available to the Parent for liquidity purposes.

Quarterly Results (Schedule of

Quarterly Results (Schedule of Quarterly Results) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended																12 Months Ended
	Dec. 31, 2020		Sep. 30, 2020		Jun. 30, 2020		Mar. 31, 2020		Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Quarterly Financial Data [Abstract]
Interest income	$ 2,760		$ 2,681		$ 2,672		$ 2,982		$ 3,039		$ 3,040		$ 2,977		$ 2,937		$ 11,095		$ 11,993		$ 10,893
Interest expense	383		416		482		584		615		638		645		632		1,865		2,530		2,139
Net interest income	2,377		2,265		2,190		2,398		2,424		2,402		2,332		2,305		9,230		9,463		8,754
Provision for credit losses	531		750		2,046		1,807		836		799		787		809		5,134	[1],[2]	3,231	[1],[2],[3]	3,035	[1],[2],[3]
Other income	447		449		472		490		520		498		520		458		1,858		1,996		1,955
Other expense	1,278		1,005		1,077		1,159		1,184		1,107		1,078		1,024		4,519		4,393		4,077
Income (loss) before income tax expense	1,015		959		(461)		(78)		924		994		987		930		1,435		3,835		3,597
Income tax expense	216		188		(93)		(17)		216		224		234		204		294		878		855
Net income	799		771		(368)		(61)		708		770		753		726		1,141		2,957		2,742
Net income allocated to common stockholders	$ 794	[4]	$ 751	[4]	$ (369)	[4]	$ (78)	[4]	$ 704	[4]	$ 749	[4]	$ 747	[4]	$ 705	[4]	$ 1,110		$ 2,926		$ 2,711
Basic earnings per common share	$ 2.59	[4]	$ 2.45	[4]	$ (1.20)	[4]	$ (0.25)	[4]	$ 2.25	[4]	$ 2.36	[4]	$ 2.32	[4]	$ 2.15	[4]	$ 3.60		$ 9.09		$ 7.81
Diluted earnings per common share	$ 2.59	[4]	$ 2.45	[4]	$ (1.20)	[4]	$ (0.25)	[4]	$ 2.25	[4]	$ 2.36	[4]	$ 2.32	[4]	$ 2.15	[4]	$ 3.60		$ 9.08		$ 7.79
[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 ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach.
[3]	Prior to the adoption of ASU No. 2016-13 on January 1, 2020, credit losses were estimated using the incurred loss approach
[4]	Because the inputs to net income allocated to common stockholders and earnings per share are calculated using weighted averages for the quarter, the sum of all four quarters may differ from the year to date amounts in the consolidated statements of income.