Discover Financial Services (DFS) 10-Q 30 Oct 19 2019 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Oct. 25, 2019
Document Information [Line Items]
Document type	10-Q
Document quarterly report	true
Document period end date	Sep. 30, 2019
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 current reporting status	Yes
Entity interactive data current	Yes
Entity filer category	Large Accelerated Filer
Smaller reporting company	false
Emerging growth company	false
Entity shell company	false
Entity common stock, shares outstanding		313,468,253
Entity central index key	0001393612
Current fiscal year end date	--12-31
Document fiscal year focus	2019
Document fiscal period focus	Q3
Amendment flag	false

Condensed Consolidated Statemen

Condensed Consolidated Statements of Financial Condition - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Assets
Cash and cash equivalents	$ 6,075	$ 13,299
Restricted cash	37	1,846
Other short-term investments	1,000	0
Investment securities (includes $10,380 and $3,133 at fair value at September 30, 2019 and December 31, 2018, respectively)	10,649	3,370
Loan receivables
Loan receivables	92,493	90,512
Allowance for loan losses	(3,299)	(3,041)
Net loan receivables	89,194	87,471
Premises and equipment, net	1,028	936
Goodwill	255	255
Intangible assets, net	159	161
Other assets	2,389	2,215
Total assets	110,786	109,553
Deposits
Interest-bearing deposit accounts	70,327	67,084
Non-interest bearing deposit accounts	694	675
Total deposits	71,021	67,759
Long-term borrowings	24,454	27,228
Accrued expenses and other liabilities	3,594	3,436
Total liabilities	99,069	98,423
Commitments, contingencies and guarantees (Notes 8, 11 and 12)
Stockholders' Equity
Common stock, par value $0.01 per share; 2,000,000,000 shares authorized; 566,604,226 and 564,851,848 shares issued at September 30, 2019 and December 31, 2018, respectively	6	6
Preferred stock, par value $0.01 per share; 200,000,000 shares authorized; 5,700 shares issued and outstanding and aggregate liquidation preference of $570 at September 30, 2019 and December 31, 2018	563	563
Additional paid-in capital	4,188	4,130
Retained earnings	20,720	18,906
Accumulated other comprehensive loss	(74)	(156)
Treasury stock, at cost; 251,623,001 and 233,406,005 shares at September 30, 2019 and December 31, 2018, respectively	(13,686)	(12,319)
Total stockholders' equity	11,717	11,130
Total liabilities and stockholders' equity	110,786	109,553
Variable Interest Entity, Primary Beneficiary [Member]
Assets
Restricted cash	37	1,846
Loan receivables
Loan receivables	31,145	33,424
Allowance for loan losses	(1,167)	(1,150)
Other assets	6	7
Deposits
Long-term borrowings	12,820	16,917
Accrued expenses and other liabilities	$ 14	$ 18

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Financial Condition (Parenthetical) - USD ($)		Sep. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Amount of total investment securities at fair value (in dollars)	[1]	$ 10,380,000,000	$ 3,133,000,000
Common stock, par value per share (in dollars per share)		$ 0.01	$ 0.01
Common stock, shares authorized		2,000,000,000	2,000,000,000
Common stock, shares issued		566,604,226	564,851,848
Preferred stock, par value per share (in dollars per share)		$ 0.01	$ 0.01
Preferred stock, shares authorized		200,000,000	200,000,000
Preferred stock, shares issued		5,700	5,700
Preferred stock, shares outstanding		5,700	5,700
Preferred stock, liquidation preference (in dollars)		$ 570,000,000	$ 570,000,000
Treasury stock, shares		251,623,001	233,406,005
[1]	Available-for-sale investment securities are reported at fair value.

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Interest income
Credit card loans	$ 2,465	$ 2,258	$ 7,223	$ 6,487
Other loans	472	437	1,389	1,275
Investment securities	53	10	120	23
Other interest income	50	76	222	201
Total interest income	3,040	2,781	8,954	7,986
Interest expense
Deposits	407	329	1,194	878
Long-term borrowings	231	229	721	656
Total interest expense	638	558	1,915	1,534
Net interest income	2,402	2,223	7,039	6,452
Provision for loan losses	799	742	2,395	2,235
Net interest income after provision for loan losses	1,603	1,481	4,644	4,217
Other income
Discount and interchange revenue, net	255	280	785	797
Protection products revenue	48	51	146	154
Loan fee income	120	103	326	294
Transaction processing revenue	52	47	146	132
Other income	23	20	73	73
Total other income	498	501	1,476	1,450
Other expense
Employee compensation and benefits	439	408	1,291	1,213
Marketing and business development	230	218	649	627
Information processing and communications	96	89	296	257
Professional fees	189	166	539	482
Premises and equipment	26	26	80	76
Other expense	127	108	354	312
Total other expense	1,107	1,015	3,209	2,967
Income before income tax expense	994	967	2,911	2,700
Income tax expense	224	247	662	645
Net income	770	720	2,249	2,055
Net income allocated to common stockholders	$ 749	$ 699	$ 2,203	$ 2,008
Basic earnings per common share (in dollars per share)	$ 2.36	$ 2.05	$ 6.83	$ 5.77
Diluted earnings per common share (in dollars per share)	$ 2.36	$ 2.05	$ 6.82	$ 5.77

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net income	$ 770	$ 720	$ 2,249	$ 2,055
Other comprehensive income, net of tax
Unrealized gains (losses) on available-for-sale investment securities, net of tax	17	(2)	119	(10)
Unrealized (losses) gains on cash flow hedges, net of tax	(8)	4	(38)	30
Unrealized pension and post-retirement plan gains, net of tax	0	0	1	1
Other comprehensive income	9	2	82	21
Comprehensive income	$ 779	$ 722	$ 2,331	$ 2,076

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Millions	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]		Treasury Stock [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	2,055				2,055
Other comprehensive income	21					21
Purchases of treasury stock	(1,600)							(1,600)
Common stock issued under employee benefit plans (in shares)			70,000
Common stock issued under employee benefit plans	5		$ 0	5
Common stock issued and stock-based compensation expense (in shares)			1,046,000
Common stock issued and stock-based compensation expense	60		$ 0	60
Dividends — common stock	(386)				(386)
Dividends — preferred stock	(31)				(31)
Preferred stock, shares outstanding, balance at end of period (in shares) at Sep. 30, 2018		6,000
Common stock, shares outstanding, balance at end of period (in shares) at Sep. 30, 2018			564,614,000
Stockholders' equity, balance at end of period at Sep. 30, 2018	11,016	$ 563	$ 6	4,107	18,354	(160)		(11,854)
Preferred stock, shares outstanding, balance at beginning of period (in shares) at Jun. 30, 2018		6,000
Common stock, shares outstanding, balance at beginning of period (in shares) at Jun. 30, 2018			564,558,000
Stockholders' equity, balance at beginning of period at Jun. 30, 2018	10,889	$ 563	$ 6	4,089	17,787	(162)		(11,394)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	720				720
Other comprehensive income	2					2
Purchases of treasury stock	(460)							(460)
Common stock issued under employee benefit plans (in shares)			25,000
Common stock issued under employee benefit plans	2		$ 0	2
Common stock issued and stock-based compensation expense (in shares)			31,000
Common stock issued and stock-based compensation expense	16		$ 0	16
Dividends — common stock	(138)				(138)
Dividends — preferred stock	(15)				(15)
Preferred stock, shares outstanding, balance at end of period (in shares) at Sep. 30, 2018		6,000
Common stock, shares outstanding, balance at end of period (in shares) at Sep. 30, 2018			564,614,000
Stockholders' equity, balance at end of period at Sep. 30, 2018	$ 11,016	$ 563	$ 6	4,107	18,354	(160)		(11,854)
Preferred stock, shares outstanding, balance at beginning of period (in shares) at Dec. 31, 2018	5,700	6,000
Common stock, shares outstanding, balance at beginning of period (in shares) at Dec. 31, 2018			564,852,000
Stockholders' equity, balance at beginning 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	2,249				2,249
Other comprehensive income	82					82
Purchases of treasury stock	(1,367)							(1,367)
Common stock issued under employee benefit plans (in shares)			76,000
Common stock issued under employee benefit plans	6		$ 0	6
Common stock issued and stock-based compensation expense (in shares)			1,676,000
Common stock issued and stock-based compensation expense	52		$ 0	52
Dividends — common stock	(404)				(404)
Dividends — preferred stock	$ (31)				(31)
Preferred stock, shares outstanding, balance at end of period (in shares) at Sep. 30, 2019	5,700	6,000
Common stock, shares outstanding, balance at end of period (in shares) at Sep. 30, 2019			566,604,000
Stockholders' equity, balance at end of period at Sep. 30, 2019	$ 11,717	$ 563	$ 6	4,188	20,720	(74)		(13,686)
Preferred stock, shares outstanding, balance at beginning of period (in shares) at Jun. 30, 2019		6,000
Common stock, shares outstanding, balance at beginning of period (in shares) at Jun. 30, 2019			566,019,000
Stockholders' equity, balance at beginning of period at Jun. 30, 2019	11,493	$ 563	$ 6	4,167	20,107	(83)		(13,267)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	770				770
Other comprehensive income	9					9
Purchases of treasury stock	(419)							(419)
Common stock issued under employee benefit plans (in shares)			25,000
Common stock issued under employee benefit plans	3		$ 0	3
Common stock issued and stock-based compensation expense (in shares)			560,000
Common stock issued and stock-based compensation expense	18		$ 0	18
Dividends — common stock	(142)				(142)
Dividends — preferred stock	$ (15)				(15)
Preferred stock, shares outstanding, balance at end of period (in shares) at Sep. 30, 2019	5,700	6,000
Common stock, shares outstanding, balance at end of period (in shares) at Sep. 30, 2019			566,604,000
Stockholders' equity, balance at end of period at Sep. 30, 2019	$ 11,717	$ 563	$ 6	$ 4,188	$ 20,720	$ (74)		$ (13,686)
[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.

Condensed Consolidated Statem_6

Condensed Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Stockholders' Equity [Abstract]
Dividends declared, common stock (dollars per share)	$ 0.44	$ 0.4	$ 1.24	$ 1.1
Dividends declared, preferred stock (dollars per share)	$ 2,750	$ 2,750	$ 5,500	$ 5,500

Condensed Consolidated Statem_7

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities
Net income	$ 2,249	$ 2,055
Adjustments to reconcile net income to net cash provided by operating activities
Provision for loan losses	2,395	2,235
Depreciation and amortization	315	326
Amortization of deferred revenues and accretion of accretable yield on acquired loans	(311)	(302)
Net loss on investments and other assets	30	33
Other, net	(36)	(122)
Changes in assets and liabilities
(Increase) decrease in other assets	(33)	43
Increase in accrued expenses and other liabilities	123	162
Net cash provided by operating activities	4,732	4,430
Cash flows from investing activities
Purchases of other short-term investments	(1,000)	0
Maturities of available-for-sale investment securities	106	802
Purchases of available-for-sale investment securities	(7,183)	(983)
Maturities of held-to-maturity investment securities	21	13
Purchases of held-to-maturity investment securities	(54)	(82)
Net principal disbursed on loans originated for investment	(3,848)	(4,318)
Purchases of other investments	(49)	(20)
Purchases of premises and equipment	(212)	(177)
Net cash used for investing activities	(12,219)	(4,765)
Cash flows from financing activities
Proceeds from issuance of securitized debt	2,027	3,076
Maturities and repayment of securitized debt	(6,278)	(3,888)
Proceeds from issuance of other long-term borrowings	1,341	2,235
Maturities and repayment of other long-term borrowings	(86)	(756)
Proceeds from issuance of common stock	6	5
Purchases of treasury stock	(1,367)	(1,600)
Net increase in deposits	3,231	4,886
Dividends paid on common and preferred stock	(420)	(401)
Net cash (used for) provided by financing activities	(1,546)	3,557
Net (decrease) increase in cash, cash equivalents and restricted cash	(9,033)	3,222
Cash, cash equivalents and restricted cash, at beginning of period	15,145	13,387
Cash, cash equivalents and restricted cash, at end of period	6,112	16,609
Reconciliation of cash, cash equivalents and restricted cash
Cash and cash equivalents	6,075	16,019
Restricted cash	$ 37	$ 590

Background and Basis of Present

Background and Basis of Presentation	9 Months Ended
	Sep. 30, 2019
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 direct 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 direct banking products and services and payment services through its subsidiaries. The Company offers its customers credit card loans, private student loans, personal loans, home equity loans and deposit products. The Company also operates the Discover Network, the PULSE network ("PULSE") and Diners Club International ("Diners Club"). 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 U.S. 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, Direct 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 15: Segment Disclosures. Basis of Presentation The accompanying condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States ("GAAP") for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete consolidated financial statements. In the opinion of management, the financial statements reflect all adjustments necessary for fair presentation of results for the interim period. All such adjustments are of a normal, recurring nature. The preparation of financial statements in conformity with GAAP requires the Company to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and related disclosures. These estimates are based on information available as of the date of the condensed consolidated financial statements. The Company believes that the estimates used in the preparation of the condensed consolidated financial statements are reasonable. Actual results could differ from these estimates. These interim condensed consolidated financial statements should be read in conjunction with the Company's 2018 audited consolidated financial statements filed with the Company's annual report on Form 10-K for the year ended December 31, 2018 . Recently Issued Accounting Pronouncements In June 2016, the Financial Accounting Standards Board issued Accounting Standards Update ("ASU") No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. This ASU replaces the incurred loss model with the current expected credit loss ("CECL") approach. For loans carried at amortized cost, the allowance for loan losses will be based on management's current estimate of all expected credit losses over the remaining contractual term of the loans. Upon the origination of a loan, the Company will have to 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 to be based on historical experience, current conditions and reasonable and supportable forecasts. The CECL approach is expected to increase the Company's allowance for loan losses as a result of: (1) recording reserves for expected losses, not simply those deemed to be already incurred, (2) extending the loss estimate period over the entire life of the loan and (3) reclassification of the credit loss component of the purchased credit-impaired ("PCI") loan portfolio out of loan carrying value and into the allowance for loan losses. The allowance for loan losses on all loans carried at amortized cost, including PCI loans and loans modified in a troubled debt restructuring ("TDR") will be measured under the CECL approach. Existing specialized measurement guidance for PCI loans, which the ASU refers to as purchased credit-deteriorated ("PCD"), and TDRs will be eliminated, although certain separate disclosure guidance will be retained. Measurement of credit impairment of available-for-sale debt securities will generally remain unchanged under the new rules, but any such impairment will be recorded through an allowance, rather than a direct write-down of the security. The Company invests in U.S. Treasury 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 U.S. government. Therefore, management has concluded that there is no expectation of nonpayment on its investment securities and will not record an allowance for credit losses on these investments. The ASU is effective for the Company on January 1, 2020. A cross-functional governance structure is in place to oversee the implementation of the standard. The Company has substantially finalized loss forecasting models and technological solutions, and is refining processes and controls in support of the new standard. Management also continues to finalize key accounting interpretations, the reversion method for periods beyond the reasonable and supportable forecast period, and the length of the reasonable and supportable forecast period and reversion period considering economic conditions. Upon adoption, the allowance for loan losses will increase with an offsetting adjustment, net of taxes, to retained earnings. Additionally, there will be an immaterial adjustment to the carrying value of PCD loans. Adoption of the standard will materially impact stockholders' equity, regulatory capital and the Company's consolidated financial condition. In addition, the Company's results of operations may be subject to more volatility. The extent of the impact upon adoption will depend on the characteristics of the Company's loan portfolio and economic conditions at that date, as well as forecasted conditions thereafter.

Investments

Investments	9 Months Ended
	Sep. 30, 2019
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): September 30, December 31, Certificates of deposit (1) $ 1,000 $ — Total other short-term investments $ 1,000 $ — U.S. Treasury securities (2) $ 9,930 $ 2,586 Residential mortgage-backed securities - Agency (3) 719 784 Total investment securities $ 10,649 $ 3,370 (1) Includes certificates of deposit with maturity dates greater than 90 days but less than one year at the time of acquisition. (2) Includes $86 million and $42 million of U.S. Treasury securities pledged as swap collateral as of September 30, 2019 and December 31, 2018 , 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 Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value At September 30, 2019 Available-for-Sale Investment Securities (1) U.S. Treasury securities $ 9,758 $ 177 $ (5 ) $ 9,930 Residential mortgage-backed securities - Agency 449 2 (1 ) 450 Total available-for-sale investment securities $ 10,207 $ 179 $ (6 ) $ 10,380 Held-to-Maturity Investment Securities (2) Residential mortgage-backed securities - Agency (3) $ 269 $ 4 $ — $ 273 Total held-to-maturity investment securities $ 269 $ 4 $ — $ 273 At December 31, 2018 Available-for-Sale Investment Securities (1) U.S. Treasury securities $ 2,559 $ 27 $ — $ 2,586 Residential mortgage-backed securities - Agency 559 — (12 ) 547 Total available-for-sale investment securities $ 3,118 $ 27 $ (12 ) $ 3,133 Held-to-Maturity Investment Securities (2) Residential mortgage-backed securities - Agency (3) $ 237 $ — $ (4 ) $ 233 Total held-to-maturity investment securities $ 237 $ — $ (4 ) $ 233 (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 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 Value Unrealized Losses Fair Value Unrealized Losses At September 30, 2019 Available-for-Sale Investment Securities U.S. Treasury securities 13 $ 1,660 $ (5 ) $ — $ — Residential mortgage-backed securities - Agency 11 $ 70 $ — $ 78 $ (1 ) Held-to-Maturity Investment Securities Residential mortgage-backed securities - Agency 22 $ 8 $ — $ 20 $ — At December 31, 2018 Available-for-Sale Investment Securities Residential mortgage-backed securities - Agency 31 $ 110 $ (1 ) $ 437 $ (11 ) Held-to-Maturity Investment Securities Residential mortgage-backed securities - Agency 90 $ 101 $ (1 ) $ 83 $ (3 ) There were no losses related to other-than-temporary impairments and no proceeds from sales or recognized gains and losses on available-for-sale securities during the three or nine months ended September 30, 2019 and 2018 . See Note 7: Accumulated Other Comprehensive Income for unrealized gains and losses on available-for-sale securities during the three and nine months ended September 30, 2019 and 2018 . Maturities of available-for-sale debt securities and held-to-maturity debt securities are provided in the following table (dollars in millions): At September 30, 2019 One Year or Less After One Year Through Five Years After Five Years Through Ten Years After Ten Years Total Available-for-Sale Investment Securities—Amortized Cost U.S. Treasury securities $ 621 $ 7,980 $ 1,157 $ — $ 9,758 Residential mortgage-backed securities - Agency (1) — 97 352 — 449 Total available-for-sale investment securities $ 621 $ 8,077 $ 1,509 $ — $ 10,207 Held-to-Maturity Investment Securities—Amortized Cost Residential mortgage-backed securities - Agency (1) $ — $ — $ — $ 269 $ 269 Total held-to-maturity investment securities $ — $ — $ — $ 269 $ 269 Available-for-Sale Investment Securities—Fair Values U.S. Treasury securities $ 624 $ 8,137 $ 1,169 $ — $ 9,930 Residential mortgage-backed securities - Agency (1) — 97 353 — 450 Total available-for-sale investment securities $ 624 $ 8,234 $ 1,522 $ — $ 10,380 Held-to-Maturity Investment Securities—Fair Values Residential mortgage-backed securities - Agency (1) $ — $ — $ — $ 273 $ 273 Total held-to-maturity investment securities $ — $ — $ — $ 273 $ 273 (1) Maturities of residential mortgage-backed securities are reflective of the contractual maturities of the investment. 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 condensed 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 condensed 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 entities. As of September 30, 2019 and December 31, 2018 , the Company had outstanding investments in these entities of $321 million and $295 million , respectively, and related contingent liabilities of $57 million and $49 million , respectively. Of the above outstanding equity investments, the Company had $299 million and $271 million of investments related to affordable housing projects as of September 30, 2019 and December 31, 2018 , respectively, which had $57 million and $30 million related contingent liabilities, respectively.

Loan Receivables

Loan Receivables	9 Months Ended
	Sep. 30, 2019
Loans and Leases Receivable Disclosure [Abstract]
Loan Receivables	Loan Receivables The Company has three loan portfolio segments: credit card loans, other loans and PCI loans. The Company's classes of receivables within the three portfolio segments are depicted in the following table (dollars in millions): September 30, December 31, Credit card loans (1) $ 73,968 $ 72,876 Other loans Personal loans 7,596 7,454 Private student loans 8,395 7,728 Other 1,193 817 Total other loans 17,184 15,999 PCI loans (2) 1,341 1,637 Total loan receivables 92,493 90,512 Allowance for loan losses (3,299 ) (3,041 ) Net loan receivables $ 89,194 $ 87,471 (1) Amounts include carrying values of $17.3 billion and $22.0 billion underlying investors' interest in trust debt at September 30, 2019 and December 31, 2018 , respectively, and $13.6 billion and $11.1 billion in seller's interest at September 30, 2019 and December 31, 2018 , respectively. See Note 4: Credit Card and Student Loan Securitization Activities for additional information. (2) Amounts include carrying values of $310 million and $363 million in loans pledged as collateral against the note issued from The Student Loan Corporation ("SLC") securitization trust at September 30, 2019 and December 31, 2018 , respectively. See Note 4: Credit Card and Student Loan Securitization Activities for additional information. Credit Quality Indicators The Company regularly reviews its collection experience (including delinquencies and net charge-offs) in determining its allowance for loan losses. Information related to the delinquent and non-accruing loans in the Company's loan portfolio is shown below by each class of loan receivables except for PCI student loans, which is shown under the heading "— Purchased Credit-Impaired Loans" (dollars in millions): 30-89 Days Delinquent 90 or More Days Delinquent Total Past Due 90 or More Days Delinquent and Accruing Total Non-accruing (1) At September 30, 2019 Credit card loans (2) $ 950 $ 897 $ 1,847 $ 809 $ 269 Other loans Personal loans (3) 79 34 113 32 12 Private student loans (excluding PCI) (4) 114 36 150 35 9 Other 3 1 4 — 14 Total other loans (excluding PCI) 196 71 267 67 35 Total loan receivables (excluding PCI) $ 1,146 $ 968 $ 2,114 $ 876 $ 304 At December 31, 2018 Credit card loans (2) $ 885 $ 887 $ 1,772 $ 781 $ 266 Other loans Personal loans (3) 84 35 119 33 11 Private student loans (excluding PCI) (4) 117 38 155 37 8 Other 2 1 3 — 17 Total other loans (excluding PCI) 203 74 277 70 36 Total loan receivables (excluding PCI) $ 1,088 $ 961 $ 2,049 $ 851 $ 302 (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 $12 million and $9 million for the three months ended September 30, 2019 and 2018 , respectively, and $34 million and $28 million for the nine months ended September 30, 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) Credit card loans that are 90 or more days delinquent and accruing interest include $148 million and $116 million of loans accounted for as TDRs at September 30, 2019 and December 31, 2018 , respectively. (3) Personal loans that are 90 or more days delinquent and accruing interest include $8 million and $5 million of loans accounted for as TDRs at September 30, 2019 and December 31, 2018 , respectively. (4) Private student loans that are 90 or more days delinquent and accruing interest include $9 million and $7 million of loans accounted for as TDRs at September 30, 2019 and December 31, 2018 , respectively. Information related to the net charge-offs in the Company's loan portfolio is shown below by each class of loan receivables except for PCI student loans, which is shown under the heading "— Purchased Credit-Impaired Loans" (dollars in millions): For the Three Months Ended September 30, 2019 2018 Net Net Charge-off (1) Net Net Charge-off (1) Credit card loans $ 611 3.32 % $ 543 3.14 % Other loans Personal loans 76 3.99 % 77 4.09 % Private student loans (excluding PCI) 14 0.69 % 22 1.19 % Other 1 — % — — % Total other loans 91 2.13 % 99 2.54 % Net charge-offs (excluding PCI) $ 702 3.09 % $ 642 3.03 % Net charge-offs (including PCI) $ 702 3.05 % $ 642 2.97 % For the Nine Months Ended September 30, 2019 2018 Net Net Charge-off (1) Net Net Charge-off (1) Credit card loans $ 1,850 3.43 % $ 1,638 3.27 % Other loans Personal loans 240 4.28 % 222 4.03 % Private student loans (excluding PCI) 44 0.73 % 65 1.17 % Other 1 — % 1 0.13 % Total other loans 285 2.30 % 288 2.52 % Net charge-offs (excluding PCI) $ 2,135 3.22 % $ 1,926 3.13 % Net charge-offs (including PCI) $ 2,135 3.17 % $ 1,926 3.06 % (1) Net charge-off rate represents net charge-off dollars (annualized) divided by average loans for the reporting period. 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. 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 a significant portion of delinquent accounts have FICO scores below 660. The following table provides the most recent FICO scores available for the Company’s customers as a percentage of each class of loan receivables: Credit Risk Profile 660 and Above Less than 660 or No Score At September 30, 2019 Credit card loans 81 % 19 % Personal loans 94 % 6 % Private student loans (excluding PCI) (1) 95 % 5 % At December 31, 2018 Credit card loans 81 % 19 % Personal loans 94 % 6 % Private student loans (excluding PCI) (1) 94 % 6 % (1) PCI loans are discussed under the heading "— Purchased Credit-Impaired Loans." For private student loans, additional credit risk management activities include monitoring the amount of loans in forbearance. Forbearance allows borrowers experiencing temporary financial difficulties and willing to make payments, the ability to temporarily suspend payments. Eligible borrowers have a lifetime cap on forbearance of 12 months . At September 30, 2019 and December 31, 2018 , there were $41 million and $37 million , respectively, of private student loans, including those classified as PCI, in forbearance, representing 0.8% and 0.7% , respectively, of total student loans in repayment and forbearance. Allowance for Loan Losses The following tables provide changes in the Company's allowance for loan losses (dollars in millions): For the Three Months Ended September 30, 2019 Credit Card Personal Loans Student Loans (1) Other Total Balance at beginning of period $ 2,691 $ 338 $ 167 $ 6 $ 3,202 Additions Provision for loan losses 719 86 (6 ) — 799 Deductions Charge-offs (784 ) (89 ) (17 ) (1 ) (891 ) Recoveries 173 13 3 — 189 Net charge-offs (611 ) (76 ) (14 ) (1 ) (702 ) Balance at end of period $ 2,799 $ 348 $ 147 $ 5 $ 3,299 For the Three Months Ended September 30, 2018 Credit Card Personal Loans Student Loans (1) Other Total Balance at beginning of period $ 2,334 $ 313 $ 170 $ 11 $ 2,828 Additions Provision for loan losses 633 87 22 — 742 Deductions Charge-offs (674 ) (86 ) (25 ) — (785 ) Recoveries 131 9 3 — 143 Net charge-offs (543 ) (77 ) (22 ) — (642 ) Other (2) — — (1 ) — (1 ) Balance at end of period $ 2,424 $ 323 $ 169 $ 11 $ 2,927 (1) Includes both PCI and non-PCI private student loans. (2) Net change in reserves on PCI pools having no remaining non-accretable difference. The following tables provide changes in the Company's allowance for loan losses (dollars in millions): For the Nine Months Ended September 30, 2019 Credit Card Personal Loans Student Loans (1) Other Total Balance at beginning of period $ 2,528 $ 338 $ 169 $ 6 $ 3,041 Additions Provision for loan losses 2,121 250 24 — 2,395 Deductions Charge-offs (2,347 ) (274 ) (54 ) (1 ) (2,676 ) Recoveries 497 34 10 — 541 Net charge-offs (1,850 ) (240 ) (44 ) (1 ) (2,135 ) Other (2) — — (2 ) — (2 ) Balance at end of period $ 2,799 $ 348 $ 147 $ 5 $ 3,299 For the Nine Months Ended September 30, 2018 Credit Card Personal Loans Student Loans (1) Other Total Balance at beginning of period $ 2,147 $ 301 $ 162 $ 11 $ 2,621 Additions Provision for loan losses 1,915 244 75 1 2,235 Deductions Charge-offs (2,021 ) (247 ) (74 ) (1 ) (2,343 ) Recoveries 383 25 9 — 417 Net charge-offs (1,638 ) (222 ) (65 ) (1 ) (1,926 ) Other (2) — — (3 ) — (3 ) Balance at end of period $ 2,424 $ 323 $ 169 $ 11 $ 2,927 (1) Includes both PCI and non-PCI private student loans. (2) Net change in reserves on PCI pools having no remaining non-accretable difference. Net charge-offs of principal are recorded against the allowance for loan 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 Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Interest and fees accrued subsequently charged off, net of recoveries (recorded as a reduction of interest income) $ 127 $ 109 $ 382 $ 328 Fees accrued subsequently charged off, net of recoveries (recorded as a reduction to other income) $ 29 $ 26 $ 90 $ 81 The following tables provide additional detail of the Company's allowance for loan losses and recorded investment in its loan portfolio by impairment methodology (dollars in millions): Credit Card Personal Loans Student Loans (1) Other Loans Total At September 30, 2019 Allowance for loans evaluated for impairment as Collectively evaluated for impairment in accordance with ASC 450-20 $ 2,297 $ 287 $ 95 $ 4 $ 2,683 Evaluated for impairment in accordance with ASC 310-10-35 (2)(3) 502 61 29 1 593 Acquired with deteriorated credit quality, evaluated in accordance with ASC 310-30 — — 23 — 23 Total allowance for loan losses $ 2,799 $ 348 $ 147 $ 5 $ 3,299 Recorded investment in loans evaluated for impairment as Collectively evaluated for impairment in accordance with ASC 450-20 $ 70,860 $ 7,401 $ 8,146 $ 1,141 $ 87,548 Evaluated for impairment in accordance with ASC 310-10-35 (2)(3) 3,108 195 249 52 3,604 Acquired with deteriorated credit quality, evaluated in accordance with ASC 310-30 — — 1,341 — 1,341 Total recorded investment $ 73,968 $ 7,596 $ 9,736 $ 1,193 $ 92,493 At December 31, 2018 Allowance for loans evaluated for impairment as Collectively evaluated for impairment in accordance with ASC 450-20 $ 2,229 $ 292 $ 121 $ 4 $ 2,646 Evaluated for impairment in accordance with ASC 310-10-35 (2)(3) 299 46 23 2 370 Acquired with deteriorated credit quality, evaluated in accordance with ASC 310-30 — — 25 — 25 Total allowance for loan losses $ 2,528 $ 338 $ 169 $ 6 $ 3,041 Recorded investment in loans evaluated for impairment as Collectively evaluated for impairment in accordance with ASC 450-20 $ 70,628 $ 7,302 $ 7,546 $ 761 $ 86,237 Evaluated for impairment in accordance with ASC 310-10-35 (2)(3) 2,248 152 182 56 2,638 Acquired with deteriorated credit quality, evaluated in accordance with ASC 310-30 — — 1,637 — 1,637 Total recorded investment $ 72,876 $ 7,454 $ 9,365 $ 817 $ 90,512 (1) Includes both PCI and non-PCI private student loans. (2) Loan receivables evaluated for impairment in accordance with Accounting Standards Codification ("ASC") 310-10-35 include credit card loans, personal loans and student loans collectively evaluated for impairment in accordance with ASC Subtopic 310-40, Receivables, which consists of modified loans accounted for as TDRs. Other loans are individually evaluated for impairment and generally do not represent TDRs. (3) The unpaid principal balance of credit card loans was $2.8 billion and $2.0 billion at September 30, 2019 and December 31, 2018 , respectively. All loans accounted for as TDRs have a related allowance for loan losses. Troubled Debt Restructurings The Company has internal loan modification programs that provide relief to credit card, personal loan and student loan borrowers who may be experiencing financial hardship. The Company continually evaluates new programs to determine which of them meet the definition of a TDR. 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. 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 considered individually impaired. In addition, loans that defaulted or graduated from modification programs or forbearance are considered to be individually impaired. For credit card customers, the Company offers temporary hardship programs consisting of an interest rate reduction and in some cases a reduced minimum payment, both lasting for a period no longer than 12 months . The permanent modification program involves 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. Modified credit card loans that are deemed to meet the definition of TDRs include loans in both temporary and permanent programs. 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 also 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 accounted for as TDRs. At September 30, 2019 , there was $5.2 billion of private student loans in repayment, which includes both PCI and non-PCI loans. 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 non-PCI modified loan typically meets the definition of a TDR based on the cumulative length of the concession period and an evaluation of the credit quality of the borrower based on FICO scores. Borrower performance after using payment programs or forbearance is monitored and the Company believes the programs help to prevent defaults and are useful in assisting customers experiencing financial difficulties. The Company plans to continue to use payment programs and forbearance and, as a result, expects to have additional loans classified as TDRs in the future. Additional information about modified loans classified as TDRs is shown below (dollars in millions): Average recorded investment in loans Interest income recognized during period loans were impaired (1) Gross interest income that would have been recorded with original terms (2) For the Three Months Ended September 30, 2019 Credit card loans (3) $ 2,960 $ 93 $ 53 Personal loans $ 188 $ 5 $ 3 Private student loans $ 239 $ 5 $ 1 For the Three Months Ended September 30, 2018 Credit card loans (3) $ 1,815 $ 48 $ 37 Personal loans $ 134 $ 4 $ 1 Private student loans $ 166 $ 3 $ — For the Nine Months Ended September 30, 2019 Credit card loans (3) $ 2,682 $ 245 $ 148 Personal loans $ 174 $ 13 $ 7 Private student loans $ 215 $ 13 $ 1 For the Nine Months Ended September 30, 2018 Credit card loans (3) $ 1,612 $ 123 $ 95 Personal loans $ 125 $ 10 $ 4 Private student loans $ 152 $ 9 $ — (1) The Company does not separately track interest income on loans in modification programs. Amounts shown are estimated by applying an average interest rate to the average loans in the various modification programs. (2) The Company does not separately track the amount of additional gross interest income that would have been recorded if the loans in modification programs had not been restructured and interest had instead been recorded in accordance with the original terms. Amounts shown are estimated by applying the difference between the average interest rate earned on non-impaired loans and the average interest rate earned on loans in the modification programs to the average loans in the modification programs. (3) Includes credit card loans that were modified in TDRs, but are no longer enrolled in a TDR program due to noncompliance with the terms of the modification or due to successful completion of a program after which charging privileges may be reinstated based on customer-level evaluation. The average balance of credit card loans that were no longer enrolled in a TDR program was $985 million and $427 million for the three months ended September 30, 2019 and 2018 , respectively, and $833 million and $404 million for the nine months ended September 30, 2019 and 2018 , respectively. In order to evaluate the primary financial effects that resulted from credit card loans entering into a loan modification program during the three and nine months ended September 30, 2019 and 2018 , the Company quantified the amount by which interest and fees were reduced during the periods. During the three months ended September 30, 2019 and 2018 , the Company forgave approximately $19 million and $12 million , respectively, of interest and fees as a result of accounts entering into a credit card loan modification program. During the nine months ended September 30, 2019 and 2018 , the Company forgave approximately $53 million and $35 million , respectively, of interest and fees as a result of accounts entering into a credit card loan modification program. The following table provides information on loans that entered a loan modification program during the period (dollars in millions): For the Three Months Ended September 30, 2019 2018 Number of Accounts Balances Number of Accounts Balances Accounts that entered a loan modification program during the period Credit card loans 97,046 $ 623 69,127 $ 444 Personal loans 2,859 $ 39 1,903 $ 27 Private student loans 1,692 $ 31 935 $ 17 For the Nine Months Ended September 30, 2019 2018 Number of Accounts Balances Number of Accounts Balances Accounts that entered a loan modification program during the period Credit card loans 273,970 $ 1,766 185,185 $ 1,187 Personal loans 8,129 $ 110 5,867 $ 79 Private student loans 4,978 $ 92 2,887 $ 54 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 Three Months Ended September 30, 2019 2018 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) 19,108 $ 109 10,535 $ 60 Personal loans (2) 1,131 $ 15 847 $ 11 Private student loans (3) 396 $ 8 278 $ 5 For the Nine Months Ended September 30, 2019 2018 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) 50,980 $ 294 28,319 $ 156 Personal loans (2) 2,925 $ 42 2,059 $ 27 Private student loans (3) 966 $ 19 753 $ 13 (1) Terms revert back to the pre-modification terms for customers who default from a temporary program and charging privileges remain revoked in most cases. (2) For credit card loans and personal loans, a customer defaults from a modification program after two consecutive missed payments. 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 three months ended September 30, 2019 and 2018 , approximately 37% and 34% , respectively, of the total balances were charged off at the end of the month in which they defaulted from a loan modification program. Of the account balances that defaulted as shown above for the nine months ended September 30, 2019 and 2018 , approximately 38% and 35% , respectively, of the total balances were charged off at the end of the month in which they defaulted from a loan modification program. For accounts that have defaulted from a loan modification program and have not been subsequently charged off, the balances are included in the allowance for loan loss analysis discussed above under "— Allowance for Loan Losses." Purchased Credit-Impaired Loans Purchased loans with evidence of credit deterioration since origination for which it is probable that not all contractually required payments will be collected are considered impaired at acquisition and are reported as PCI loans. The private student loans acquired in the SLC transaction, as well as the additional acquired private student loan portfolio comprise the Company's only PCI loans at September 30, 2019 and December 31, 2018 . Total PCI student loans had an outstanding balance of $1.4 billion and $1.7 billion , including accrued interest, and a related carrying amount of $1.3 billion and $1.6 billion as of September 30, 2019 and December 31, 2018 , respectively. The following table provides changes in accretable yield for the acquired loans during each period (dollars in millions): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Balance at beginning of period $ 508 $ 608 $ 548 $ 669 Accretion into interest income (29 ) (34 ) (92 ) (106 ) Other changes in expected cash flows — 1 23 12 Balance at end of period $ 479 $ 575 $ 479 $ 575 Periodically, the Company updates the estimate of cash flows expected to be collected based on management's latest expectations of future net credit losses, borrower prepayments and certain other assumptions that affect cash flows. No provision expense was recorded during the three or nine months ended September 30, 2019 and 2018 . The allowance for PCI loan losses at September 30, 2019 and December 31, 2018 was $23 million and $25 million , respectively. For the nine months ended September 30, 2019 and three and nine months ended September 30, 2018 , the increase in accretable yield was primarily driven by changes in rates on variable-rate loans. There were no changes in the cash flow assumption for the three months ended September 30, 2019 . Changes to accretable yield are recognized prospectively as an adjustment to yield over the remaining life of the pools. At September 30, 2019 , the 30 or more days delinquency and 90 or more days delinquency rates on PCI student loans (which include loans not yet in repayment) were 2.90% and 0.72% , respectively. At December 31, 2018 , the 30 or more days delinquency and 90 or more days delinquency rates on PCI student loans (which include loans not yet in repayment) were 2.93% and 0.78% , respectively. These rates include private student loans that are greater than 120 days delinquent that are covered by an indemnification agreement or insurance arrangements through which the Company expects to recover a substantial portion of the loan. The net charge-off rate on PCI student loans was 0.32% and 0.64% for the three months ended September 30, 2019 and 2018 , respectively, and 0.33% and 0.71% for the nine months ended September 30, 2019 and 2018 , respectively.

Credit Card and Student Loan Se

Credit Card and Student Loan Securitization Activities	9 Months Ended
	Sep. 30, 2019
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 to the consolidated financial statements of the Company's annual report on Form 10-K for the year ended December 31, 2018 . Credit Card Securitization Activities The Company accesses the term asset securitization market through the Discover Card Master Trust I ("DCMT") and the Discover Card Execution Note Trust ("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 estimated probable incurred loss is included in the allowance for loan 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 condensed 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 condensed consolidated statements of financial condition as relating to securitization activities, are shown in the following table (dollars in millions): September 30, December 31, Restricted cash $ 26 $ 1,834 Investors' interests held by third-party investors 12,600 16,800 Investors' interests held by wholly-owned subsidiaries of Discover Bank 4,657 5,211 Seller's interest 13,578 11,050 Loan receivables (1) 30,835 33,061 Allowance for loan losses allocated to securitized loan receivables (1) (1,167 ) (1,150 ) Net loan receivables 29,668 31,911 Other 6 7 Carrying value of assets of consolidated variable interest entities $ 29,700 $ 33,752 (1) The Company maintains its allowance for loan losses at an amount sufficient to absorb probable losses inherent in 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. 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 September 30, 2019 , 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 Student loan trust receivables underlying third-party investors' interests are recorded in PCI loans and the related debt issued by the trusts is reported in long-term borrowings. The assets of the trusts 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 trusts. With the exception of the trusts' restricted assets, the trusts and investors have no recourse to the Company's other assets or the Company's general credit for a shortage in cash flows. Currently there is one trust from which issued securities remain outstanding to investors. Principal payments on the long-term secured borrowings are made as cash is collected on the underlying loans that are used as 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 accounts that generate 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 condensed consolidated statements of financial condition as relating to securitization activities, are shown in the following table (dollars in millions): September 30, December 31, Restricted cash $ 11 $ 12 Student loan receivables 310 363 Carrying value of assets of consolidated variable interest entities $ 321 $ 375

Deposits

Deposits	9 Months Ended
	Sep. 30, 2019
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): September 30, December 31, Certificates of deposit in amounts less than $100,000 $ 25,248 $ 27,947 Certificates of deposit in amounts $100,000 or greater (1) 8,736 6,841 Savings deposits, including money market deposit accounts 36,343 32,296 Total interest-bearing deposits $ 70,327 $ 67,084 (1) Includes $2.4 billion and $1.7 billion in certificates of deposit equal to or greater than $250,000, the Federal Deposit Insurance Corporation ("FDIC") insurance limit, as of September 30, 2019 and December 31, 2018 , respectively. The following table summarizes certificates of deposit in amounts of $100,000 or greater by contractual maturity (dollars in millions): September 30, 2019 Three months or less $ 1,370 Over three months through six months 1,502 Over six months through twelve months 3,311 Over twelve months 2,553 Total $ 8,736 The following table summarizes certificates of deposit maturing over the remainder of this year, over each of the next four years, and thereafter (dollars in millions): September 30, 2019 2019 $ 4,122 2020 15,328 2021 6,382 2022 3,178 2023 1,896 Thereafter 3,078 Total $ 33,984

Long-Term Borrowings

Long-Term Borrowings	9 Months Ended
	Sep. 30, 2019
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): September 30, 2019 December 31, 2018 Maturity Interest Weighted-Average Interest Rate Outstanding Amount Outstanding Amount Securitized Debt Fixed-rate asset-backed securities (1) 2020-2024 1.39%-3.32% 2.58% $ 7,637 $ 10,657 Floating-rate asset-backed securities (2)(3) 2020-2024 2.26%-2.63% 2.41% 5,014 6,063 Total Discover Card Master Trust I and Discover Card Execution Note Trust 12,651 16,720 Floating-rate asset-backed security (4)(5) 2031 6.00% 6.00% 169 197 Total SLC Private Student Loan Trust 169 197 Total long-term borrowings - owed to securitization investors 12,820 16,917 Discover Financial Services (Parent Company) Fixed-rate senior notes 2022-2027 3.75%-5.20% 4.16% 3,287 2,743 Fixed-rate retail notes 2019-2031 2.85%-4.60% 3.73% 339 346 Discover Bank Fixed-rate senior bank notes (1) 2020-2028 2.45%-4.65% 3.55% 6,811 6,027 Fixed-rate subordinated bank notes 2019-2028 4.68%-8.70% 6.32% 1,197 1,195 Total long-term borrowings $ 24,454 $ 27,228 (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 14: 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 September 30, 2019 . (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 14: Derivatives and Hedging Activities. (4) SLC Private Student Loan Trust floating-rate asset-backed security includes an issuance with the following interest rate term: Prime rate + 100 basis points as of September 30, 2019 . (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 the remainder of this year, over each of the next four years, and thereafter (dollars in millions): September 30, 2019 2019 $ 200 2020 4,745 2021 4,218 2022 4,124 2023 3,329 Thereafter 7,838 Total $ 24,454 The Company has access to committed borrowing capacity through private securitizations to support the funding of its credit card loan receivables. As of September 30, 2019 , the total commitment of secured credit facilities through private providers was $6.0 billion , none of which was drawn as of September 30, 2019 . 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 expirations in calendar years 2021 through 2022. Borrowings outstanding under each facility bear interest at a margin above LIBOR or the asset-backed commercial paper costs of each individual conduit provider. The terms of each agreement provide for a commitment fee to be paid on the unused capacity and include various affirmative and negative covenants, including performance metrics and legal requirements similar to those required to issue any term securitization transaction.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income	9 Months Ended
	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income	Accumulated Other Comprehensive Income Changes in each component of accumulated other comprehensive income (loss) ("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 Three Months Ended September 30, 2019 Balance at June 30, 2019 $ 112 $ (8 ) $ (187 ) $ (83 ) Net change 17 (8 ) — 9 Balance at September 30, 2019 $ 129 $ (16 ) $ (187 ) $ (74 ) For the Three Months Ended September 30, 2018 Balance at June 30, 2018 $ (14 ) $ 39 $ (187 ) $ (162 ) Net change (2 ) 4 — 2 Balance at September 30, 2018 $ (16 ) $ 43 $ (187 ) $ (160 ) For the Nine Months Ended September 30, 2019 Balance at December 31, 2018 $ 10 $ 22 $ (188 ) $ (156 ) Net change 119 (38 ) 1 82 Balance at September 30, 2019 $ 129 $ (16 ) $ (187 ) $ (74 ) For the Nine Months Ended September 30, 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 (10 ) 30 1 21 Balance at September 30, 2018 $ (16 ) $ 43 $ (187 ) $ (160 ) (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 other comprehensive income (loss) ("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 Three Months Ended September 30, 2019 Available-for-Sale Investment Securities Net unrealized holding gains arising during the period $ 24 $ (7 ) $ 17 Net change $ 24 $ (7 ) $ 17 Cash Flow Hedges Net unrealized losses arising during the period $ (9 ) $ 2 $ (7 ) Amounts reclassified from AOCI (2 ) 1 (1 ) Net change $ (11 ) $ 3 $ (8 ) For the Three Months Ended September 30, 2018 Available-for-Sale Investment Securities Net unrealized holding losses arising during the period $ (4 ) $ 2 $ (2 ) Net change $ (4 ) $ 2 $ (2 ) Cash Flow Hedges Net unrealized gains arising during the period $ 8 $ (2 ) $ 6 Amounts reclassified from AOCI (2 ) — (2 ) Net change $ 6 $ (2 ) $ 4 For the Nine Months Ended September 30, 2019 Available-for-Sale Investment Securities Net unrealized holding gains arising during the period $ 158 $ (39 ) $ 119 Net change $ 158 $ (39 ) $ 119 Cash Flow Hedges Net unrealized losses arising during the period $ (44 ) $ 11 $ (33 ) Amounts reclassified from AOCI (7 ) 2 (5 ) Net change $ (51 ) $ 13 $ (38 ) Pension Plan Unrealized gains arising during the period $ 1 $ — $ 1 Net change $ 1 $ — $ 1 For the Nine Months Ended September 30, 2018 Available-for-Sale Investment Securities Net unrealized holding losses arising during the period $ (14 ) $ 4 $ (10 ) Net change $ (14 ) $ 4 $ (10 ) Cash Flow Hedges Net unrealized gains arising during the period $ 42 $ (10 ) $ 32 Amounts reclassified from AOCI (2 ) — (2 ) Net change $ 40 $ (10 ) $ 30 Pension Plan Unrealized gains arising during the period $ 1 $ — $ 1 Net change $ 1 $ — $ 1

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The following table presents the calculation of the Company's effective income tax rate (dollars in millions, except effective income tax rate): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Income before income tax expense $ 994 $ 967 $ 2,911 $ 2,700 Income tax expense $ 224 $ 247 $ 662 $ 645 Effective income tax rate 22.5 % 25.5 % 22.7 % 23.9 % The effective tax rates decreased 3.0 percentage points and 1.2 percentage points , respectively, for the three and nine months ended September 30, 2019 as compared to the same periods in 2018 . For the three months ended September 30, 2019, the effective tax rate was lower because the same period in 2018 included an increase in reserves for certain tax matters. For the three and nine months ended September 30, 2019, the effective tax rate was favorably impacted by the resolution of certain tax matters. The Company is subject to examination by the Internal Revenue Service ("IRS") and tax authorities in various state, local and foreign tax jurisdictions. The Company regularly assesses the likelihood of additional assessments or settlements in each of the taxing jurisdictions resulting from these and subsequent years' examinations. The IRS is currently examining the years 2011-2015. At this time, the potential change in unrecognized tax benefits is not expected to be significant over the next 12 months. 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	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share The following table presents the calculation of basic and diluted earnings per share ("EPS") (in millions, except per share amounts): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Numerator Net income $ 770 $ 720 $ 2,249 $ 2,055 Preferred stock dividends (15 ) (15 ) (31 ) (31 ) Net income available to common stockholders 755 705 2,218 2,024 Income allocated to participating securities (6 ) (6 ) (15 ) (16 ) Net income allocated to common stockholders $ 749 $ 699 $ 2,203 $ 2,008 Denominator Weighted-average shares of common stock outstanding 317 341 323 348 Effect of dilutive common stock equivalents — 1 — — Weighted-average shares of common stock outstanding and common stock equivalents 317 342 323 348 Basic earnings per common share $ 2.36 $ 2.05 $ 6.83 $ 5.77 Diluted earnings per common share $ 2.36 $ 2.05 $ 6.82 $ 5.77 Anti-dilutive securities were not material and had no impact on the computation of diluted EPS for the three or nine months ended September 30, 2019 and 2018 .

Capital Adequacy

Capital Adequacy	9 Months Ended
	Sep. 30, 2019
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 main 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 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 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 will be replaced with new permanent rules effective in April 2020 with the option to early adopt beginning on January 1, 2020. As of September 30, 2019 , 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 Requirements Capital Requirements To Be Classified as Well-Capitalized Amount Ratio (1) Amount Ratio Amount (2) Ratio (2) September 30, 2019 Total capital (to risk-weighted assets) Discover Financial Services $ 13,009 13.7 % $ 7,598 ≥8.0% $ 9,498 ≥10.0% Discover Bank $ 13,354 14.2 % $ 7,515 ≥8.0% $ 9,394 ≥10.0% Tier 1 capital (to risk-weighted assets) Discover Financial Services $ 11,403 12.0 % $ 5,699 ≥6.0% $ 5,699 ≥6.0% Discover Bank $ 11,157 11.9 % $ 5,637 ≥6.0% $ 7,515 ≥8.0% Tier 1 capital (to average assets) Discover Financial Services $ 11,403 10.3 % $ 4,409 ≥4.0% N/A N/A Discover Bank $ 11,157 10.2 % $ 4,362 ≥4.0% $ 5,452 ≥5.0% Common Equity Tier 1 (to risk-weighted assets) Discover Financial Services $ 10,840 11.4 % $ 4,274 ≥4.5% N/A N/A Discover Bank $ 11,157 11.9 % $ 4,227 ≥4.5% $ 6,106 ≥6.5% December 31, 2018 Total capital (to risk-weighted assets) Discover Financial Services $ 12,532 13.5 % $ 7,450 ≥8.0% $ 9,312 ≥10.0% Discover Bank $ 13,106 14.2 % $ 7,372 ≥8.0% $ 9,215 ≥10.0% Tier 1 capital (to risk-weighted assets) Discover Financial Services $ 10,895 11.7 % $ 5,587 ≥6.0% $ 5,587 ≥6.0% Discover Bank $ 10,834 11.8 % $ 5,529 ≥6.0% $ 7,372 ≥8.0% Tier 1 capital (to average assets) Discover Financial Services $ 10,895 10.1 % $ 4,308 ≥4.0% N/A N/A Discover Bank $ 10,834 10.2 % $ 4,265 ≥4.0% $ 5,332 ≥5.0% Common Equity Tier 1 (to risk-weighted assets) Discover Financial Services $ 10,332 11.1 % $ 4,191 ≥4.5% N/A N/A Discover Bank $ 10,834 11.8 % $ 4,147 ≥4.5% $ 5,990 ≥6.5% (1) Capital ratios are calculated based on the Basel III Standardized Approach rules, subject to applicable 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	9 Months Ended
	Sep. 30, 2019
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 September 30, 2019 , the Company had unused credit arrangements for loans of approximately $206.8 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. Contingencies See Note 12: 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 condensed 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. • 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. T he 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. I n 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 $200 million as of September 30, 2019 . 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 September 30, 2019 , the Company had not recorded any contingent liability in the condensed 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 three or nine months ended September 30, 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 (in millions): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Aggregate sales transaction volume (1) $ 44,332 $ 40,806 $ 125,922 $ 116,800 (1) Represents period 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 condensed consolidated financial statements for merchant chargeback guarantees as of September 30, 2019 or December 31, 2018 . 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 September 30, 2019 and December 31, 2018 , the Company had escrow deposits and settlement withholdings of $8 million and $10 million , respectively, which are recorded in interest-bearing deposit accounts and accrued expenses and other liabilities on the Company's condensed consolidated statements of financial condition.

Litigation and Regulatory Matte

Litigation and Regulatory Matters	9 Months Ended
	Sep. 30, 2019
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 condensed consolidated financial statements, increase its cost of operations, or limit its ability to execute its business strategies and engage in certain business activities. For example, the Company is currently the subject of an action by the Federal Reserve with respect to anti-money laundering and related compliance programs as referred to below. In addition, 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. The existing supervisory action related to anti-money laundering and related laws and regulations will limit for a period of time the Company's ability to enter into certain types of acquisitions and make certain types of investments. 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 not material for the three and nine months ended September 30, 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 $125 million . This estimated range of reasonably possible losses is based upon currently available information for those proceedings in which the Company is involved, takes into account the Company's best estimate of such losses for those matters for which an estimate can be made, and 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 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 be material to the Company's condensed 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, and could adversely affect the Company's reputation. On May 26, 2015, the Company entered into a written agreement with the Federal Reserve Bank of Chicago where the Company agreed to enhance the Company's enterprise-wide anti-money laundering and related compliance programs. The agreement does not include civil money penalties. 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 resolving the agency's investigation with respect to certain student loan servicing practices. The CFPB's investigation into these practices has been previously disclosed by the Company, initially in February 2014. The order required the Discover Subsidiaries to provide redress of approximately $16 million to consumers who may have been affected by the activities described in the order related to certain collection calls, overstatements of minimum payment due amounts in billing statements, and provision of interest paid information to consumers, and provide regulatory disclosures with respect to loans acquired in default. In addition, the Discover Subsidiaries were required to pay a $2.5 million civil money penalty to the CFPB. As required by the consent order, on October 19, 2015, the Discover Subsidiaries submitted to the CFPB a redress plan and a compliance plan designed to ensure that the Discover Subsidiaries provide redress and otherwise comply with the terms of the order. On March 8, 2016, a class action lawsuit was filed against the Company, other credit card networks, other issuing banks, and EMVCo in the U.S. 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 violations of the Sherman Antitrust Act, California's Cartwright Act, and unjust enrichment. Plaintiffs allege a conspiracy by defendants to shift fraud liability to merchants with the migration to the EMV security standard and chip technology. Plaintiffs assert joint and several liability among the defendants and seek unspecified damages, including treble damages, attorneys' fees, costs and injunctive relief. On July 15, 2016, plaintiffs filed an amended complaint that includes additional named plaintiffs, reasserts the original claims, and includes additional state law causes of action. On September 30, 2016, the court granted the motions to dismiss for certain issuing banks and EMVCo but denied the motions to dismiss filed by the networks, including the Company. 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 March 11, 2018, the Court entered an order denying the plaintiffs' motion for class certification without prejudice to filing a renewed motion. Plaintiffs filed a renewed motion for class certification on July 16, 2018 and opening merits expert reports on October 5, 2018. Defendants filed their Opposition to Class Certification on March 15, 2019. Briefing and expert discovery related to class certification has ended; and a hearing date on class certification is yet to be scheduled. 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. On September 20, 2019, a putative class action was filed against the Company in the Northern District of Illinois alleging violations of the Telephone Consumer Protection Act. The plaintiff alleges the Company placed telephone calls to wrong or reassigned cellular telephone numbers without consent. The plaintiff seeks an injunction, statutory damages, treble damages, reasonable attorney fees, costs and expenses. 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 plaintiff.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2019
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. For transfers in and out of the levels of the fair value hierarchy, the Company discloses the fair value measurement based on the value immediately preceding the transfer. 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 for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Balance at September 30, 2019 Assets Fair value - OCI U.S. Treasury securities $ 9,930 $ — $ — $ 9,930 Residential mortgage-backed securities - Agency — 450 — 450 Available-for-sale investment securities $ 9,930 $ 450 $ — $ 10,380 Liabilities Fair value - OCI Derivative financial instruments - cash flow hedges (1) $ — $ 3 $ — $ 3 Fair value - Net income Derivative financial instruments - fair value hedges (1) $ — $ 1 $ — $ 1 Balance at December 31, 2018 Assets Fair value - OCI U.S. Treasury securities $ 2,586 $ — $ — $ 2,586 Residential mortgage-backed securities - Agency — 547 — 547 Available-for-sale investment securities $ 2,586 $ 547 $ — $ 3,133 Derivative financial instruments - cash flow hedges (1) $ — $ 8 $ — $ 8 Fair value - Net income Derivative financial instruments - fair value hedges (1) $ — $ 5 $ — $ 5 Liabilities Fair value - OCI Derivative financial instruments - cash flow hedges (1) $ — $ 2 $ — $ 2 (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 condensed consolidated statements of financial condition. There were no transfers between Levels 1 and 2 within the fair value hierarchy for the three or nine months ended September 30, 2019 and 2018 . Available-for-Sale Investment Securities Investment securities classified as available-for-sale consist of U.S. Treasury securities and residential mortgage-backed securities. The fair value estimates of investment securities classified as Level 1, consisting of U.S. 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 amongst 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 September 30, 2019 , amounts reported in residential mortgage-backed securities reflect government-rated obligations issued by Fannie Mae, Freddie Mac and Ginnie Mae with a par value of $442 million , a weighted-average coupon of 2.81% and a weighted-average remaining maturity of two 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 amongst 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. 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 had no impairments related to these assets during the three or nine months ended September 30, 2019 and 2018 . 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 September 30, 2019 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Carrying Value Assets Amortized cost Residential mortgage-backed securities - Agency $ — $ 273 $ — $ 273 $ 269 Held-to-maturity investment securities $ — $ 273 $ — $ 273 $ 269 Net loan receivables $ — $ — $ 92,855 $ 92,855 $ 89,194 Carrying value approximates fair value (1) Cash and cash equivalents $ 6,075 $ — $ — $ 6,075 $ 6,075 Restricted cash $ 37 $ — $ — $ 37 $ 37 Other short-term investments $ 1,000 $ — $ — $ 1,000 $ 1,000 Accrued interest receivables (2) $ — $ 1,054 $ — $ 1,054 $ 1,054 Liabilities Amortized cost Time deposits (3) $ — $ 34,478 $ — $ 34,478 $ 33,984 Long-term borrowings - owed to securitization investors $ — $ 12,729 $ 185 $ 12,914 $ 12,820 Other long-term borrowings — 12,348 — 12,348 11,634 Long-term borrowings $ — $ 25,077 $ 185 $ 25,262 $ 24,454 Carrying value approximates fair value (1) Accrued interest payables (2) $ — $ 243 $ — $ 243 $ 243 (1) The carrying values of these assets and liabilities approximate fair value due to the nature of their liquidity (i.e., due or payable in less than one year). (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 condensed consolidated statements of financial condition. (3) Excludes deposits without contractually defined maturities for all periods presented. 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, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Carrying Value Assets Amortized cost Residential mortgage-backed securities - Agency $ — $ 233 $ — $ 233 $ 237 Held-to-maturity investment securities $ — $ 233 $ — $ 233 $ 237 Net loan receivables $ — $ — $ 90,787 $ 90,787 $ 87,471 Carrying value approximates fair value (1) Cash and cash equivalents $ 13,299 $ — $ — $ 13,299 $ 13,299 Restricted cash $ 1,846 $ — $ — $ 1,846 $ 1,846 Accrued interest receivables (2) $ — $ 951 $ — $ 951 $ 951 Liabilities Amortized cost Time deposits (3) $ — $ 34,635 $ — $ 34,635 $ 34,788 Long-term borrowings - owed to securitization investors $ — $ 16,701 $ 217 $ 16,918 $ 16,917 Other long-term borrowings — 10,325 — 10,325 10,311 Long-term borrowings $ — $ 27,026 $ 217 $ 27,243 $ 27,228 Carrying value approximates fair value (1) Accrued interest payables (2) $ — $ 292 $ — $ 292 $ 292 (1) The carrying values of these assets and liabilities approximate fair value due to the nature of their liquidity (i.e., due or payable in less than one year). (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 condensed consolidated statements of financial condition. (3) Excludes deposits without contractually defined maturities for all periods presented.

Derivatives and Hedging Activit

Derivatives and Hedging Activities	9 Months Ended
	Sep. 30, 2019
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 13: Fair Value Measurements for a description of the valuation methodologies of 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 condensed consolidated statements of financial condition. Collateral amounts recorded in the condensed 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 payments on credit card securitized debt and deposits. The Company's outstanding cash flow hedges are for an initial maximum period of seven years for securitized debt and deposits. The derivatives are designated as hedges of the risk of changes in cash flows on the Company's LIBOR or 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 September 30, 2019 will be reclassified to interest expense as interest payments are accrued on certain of the Company's floating-rate securitized debt and deposits. During the next 12 months, the Company estimates it will reclassify $5 million of pretax expense to interest expense 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 or other senior notes, and deposits 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 and deposits relating to the risk being hedged are recorded in interest expense. The changes generally provide substantial offset to one another, with any difference in interest expense. 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 The legal characterization of 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 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): September 30, 2019 December 31, 2018 Notional Amount Number of Outstanding Derivative Contracts Derivative Assets Derivative Liabilities Notional Amount Derivative Assets Derivative Liabilities Derivatives designated as hedges Interest rate swaps—cash flow hedge $ 1,650 4 $ — $ 3 $ 2,450 $ 8 $ 2 Interest rate swaps—fair value hedge $ 9,000 12 — 1 $ 8,000 5 — Derivatives not designated as hedges Foreign exchange forward contracts (1) $ 34 7 — — $ 33 — — Total gross derivative assets/liabilities (2) — 4 13 2 Less: collateral held/posted (3) — (4 ) (8 ) (2 ) Total net derivative assets/liabilities $ — $ — $ 5 $ — (1) The foreign exchange forward contracts have notional amounts of EUR 9 million , GBP 12 million , SGD 1 million and INR 596 million as of September 30, 2019 and notional amounts of EUR 9 million , GBP 12 million , SGD 1 million and INR 464 million as of December 31, 2018 . (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 September 30, 2019 , the Company had one outstanding contract with a notional amount of $27 million and immaterial fair value. At December 31, 2018 , the Company had one outstanding contract with a notional amount of $79 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 adjustment for fair value hedges (dollars in millions): September 30, 2019 December 31, 2018 Carrying Amount of Hedged Assets/Liabilities Cumulative Amount of Fair Value Hedging Adjustment Increasing (Decreasing) the Carrying Amount of Hedged Assets/Liabilities Carrying Amount of Hedged Assets/Liabilities Cumulative Amount of Fair Value Hedging Adjustment Increasing (Decreasing) the Carrying Amount of Hedged Assets/Liabilities Long-term borrowings $ 9,046 $ 69 $ 7,893 $ (91 ) The following table summarizes the impact of the derivative instruments on income and indicates where within the condensed consolidated financial statements such impact is reported (dollars in millions): Location and Amount of (Losses) Gains Recognized in Income Interest (Expense) Deposits Long-Term Borrowings Other Income For the Three Months Ended September 30, 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 $ (407 ) $ (231 ) $ 23 The effects of cash flow and fair value hedging Gains on cash flow hedging relationship Amounts reclassified from OCI into earnings $ 1 $ 1 $ — Gains (losses) on fair value hedging relationship Gains (losses) on hedged items $ — $ (20 ) $ — Gains on interest rate swaps — 12 — Total gains (losses) on fair value hedges $ — $ (8 ) $ — The effects of derivatives not designated in hedging relationships Gains on derivatives not designated as hedges $ — $ — $ 1 For the Three Months Ended September 30, 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 $ (329 ) $ (229 ) $ 20 The effects of cash flow and fair value hedging Gains on cash flow hedging relationship Amounts reclassified from OCI into earnings $ — $ 2 $ — Gains (losses) on fair value hedging relationship Gains on hedged items $ — $ 2 $ — Gains (losses) on interest rate swaps — (14 ) — Total gains (losses) on fair value hedges $ — $ (12 ) $ — The effects of derivatives not designated in hedging relationships Gains on derivatives not designated as hedges $ — $ — $ 1 The following table summarizes the impact of the derivative instruments on income and indicates where within the condensed consolidated financial statements such impact is reported (dollars in millions): Location and Amount of (Losses) Gains Recognized in Income Interest (Expense) Deposits Long-Term Borrowings Other Income For the Nine Months Ended September 30, 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 $ (1,194 ) $ (721 ) $ 73 The effects of cash flow and fair value hedging Gains on cash flow hedging relationship Amounts reclassified from OCI into earnings $ 3 $ 4 $ — Gains (losses) on fair value hedging relationship Gains (losses) on hedged items $ — $ (160 ) $ — Gains on interest rate swaps — 128 — Total gains (losses) on fair value hedges $ — $ (32 ) $ — The effects of derivatives not designated in hedging relationships Gains on derivatives not designated as hedges $ — $ — $ 1 For the Nine Months Ended September 30, 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 $ (878 ) $ (656 ) $ 73 The effects of cash flow and fair value hedging (Losses) gains on cash flow hedging relationship Amounts reclassified from OCI into earnings $ (1 ) $ 3 $ — Gains (losses) on fair value hedging relationship Gains on hedged items $ — $ 61 $ — Gains (losses) on interest rate swaps — (88 ) — Total gains (losses) on fair value hedges $ — $ (27 ) $ — The effects of derivatives not designated in hedging relationships Gains on derivatives not designated as hedges $ — $ — $ 2 For the impact of the derivative instruments on OCI, see Note 7: 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 September 30, 2019 , 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 September 30, 2019 would have been $20 million . DFS (Parent Company) had no outstanding derivatives as of September 30, 2019 , 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	9 Months Ended
	Sep. 30, 2019
Segment Reporting [Abstract]
Segment Disclosures	Segment Disclosures The Company's business activities are managed in two segments: Direct Banking and Payment Services. • Direct Banking: The Direct 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 equity loans, and other consumer lending and deposit products. The majority of Direct 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 Direct Banking segment. • Through its operation of the Discover Network, the Direct 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): Direct Banking Payment Services Total For the Three Months Ended September 30, 2019 Interest income Credit card loans $ 2,465 $ — $ 2,465 Private student loans 175 — 175 PCI student loans 29 — 29 Personal loans 249 — 249 Other 122 — 122 Total interest income 3,040 — 3,040 Interest expense 638 — 638 Net interest income 2,402 — 2,402 Provision for loan losses 799 — 799 Other income 409 89 498 Other expense 1,069 38 1,107 Income before income tax expense $ 943 $ 51 $ 994 For the Three Months Ended September 30, 2018 Interest income Credit card loans $ 2,258 $ — $ 2,258 Private student loans 154 — 154 PCI student loans 34 — 34 Personal loans 238 — 238 Other 97 — 97 Total interest income 2,781 — 2,781 Interest expense 558 — 558 Net interest income 2,223 — 2,223 Provision for loan losses 742 — 742 Other income 421 80 501 Other expense 979 36 1,015 Income before income tax expense $ 923 $ 44 $ 967 The following table presents segment data (dollars in millions): Direct Banking Payment Services Total For the Nine Months Ended September 30, 2019 Interest income Credit card loans $ 7,223 $ — $ 7,223 Private student loans 520 — 520 PCI student loans 92 — 92 Personal loans 727 — 727 Other 391 1 392 Total interest income 8,953 1 8,954 Interest expense 1,915 — 1,915 Net interest income 7,038 1 7,039 Provision for loan losses 2,395 — 2,395 Other income 1,217 259 1,476 Other expense 3,097 112 3,209 Income before income tax expense $ 2,763 $ 148 $ 2,911 For the Nine Months Ended September 30, 2018 Interest income Credit card loans $ 6,487 $ — $ 6,487 Private student loans 451 — 451 PCI student loans 106 — 106 Personal loans 693 — 693 Other 249 — 249 Total interest income 7,986 — 7,986 Interest expense 1,534 — 1,534 Net interest income 6,452 — 6,452 Provision for loan losses 2,235 — 2,235 Other income 1,213 237 1,450 Other expense 2,859 108 2,967 Income before income tax expense $ 2,571 $ 129 $ 2,700

Revenue from Contracts with Cus

Revenue from Contracts with Customers	9 Months Ended
	Sep. 30, 2019
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): Direct Banking Payment Services Total For the Three Months Ended September 30, 2019 Other income subject to ASC 606 Discount and interchange revenue, net (1) $ 238 $ 17 $ 255 Protection products revenue 48 — 48 Transaction processing revenue — 52 52 Other income 3 20 23 Total other income subject to ASC 606 (2) 289 89 378 Other income not subject to ASC 606 Loan fee income 120 — 120 Total other income not subject to ASC 606 120 — 120 Total other income by operating segment $ 409 $ 89 $ 498 For the Three Months Ended September 30, 2018 Other income subject to ASC 606 Discount and interchange revenue, net (1) $ 266 $ 14 $ 280 Protection products revenue 51 — 51 Transaction processing revenue — 47 47 Other income 1 19 20 Total other income subject to ASC 606 (2) 318 80 398 Other income not subject to ASC 606 Loan fee income 103 — 103 Total other income not subject to ASC 606 103 — 103 Total other income by operating segment $ 421 $ 80 $ 501 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): Direct Banking Payment Services Total For the Nine Months Ended September 30, 2019 Other income subject to ASC 606 Discount and interchange revenue, net (1) $ 738 $ 47 $ 785 Protection products revenue 146 — 146 Transaction processing revenue — 146 146 Other income 7 66 73 Total other income subject to ASC 606 (2) 891 259 1,150 Other income not subject to ASC 606 Loan fee income 326 — 326 Total other income not subject to ASC 606 326 — 326 Total other income by operating segment $ 1,217 $ 259 $ 1,476 For the Nine Months Ended September 30, 2018 Other income subject to ASC 606 Discount and interchange revenue, net (1) $ 758 $ 39 $ 797 Protection products revenue 154 — 154 Transaction processing revenue — 132 132 Other income 7 66 73 Total other income subject to ASC 606 (2) 919 237 1,156 Other income not subject to ASC 606 Loan fee income 294 — 294 Total other income not subject to ASC 606 294 — 294 Total other income by operating segment $ 1,213 $ 237 $ 1,450 (1) Net of rewards, including Cashback Bonus rewards, of $520 million and $473 million for the three months ended September 30, 2019 and 2018 , respectively, and $1.4 billion and $1.3 billion for the nine months ended September 30, 2019 and 2018 , respectively. (2) Excludes $2 million of deposit product fees that are reported within net interest income for the nine months ended September 30, 2019 and 2018 and $1 million for the three months ended September 30, 2018 . Deposit product fees were immaterial for the three months ended September 30, 2019 . For a detailed description of the Company's significant revenue recognition accounting policies, 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, 2018 .

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2019
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events The Company has evaluated events and transactions that have occurred subsequent to September 30, 2019 and determined that there were no subsequent events that would require recognition or disclosure in the condensed consolidated financial statements.

Background and Basis of Prese_2

Background and Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Significant Accounting Policies	The accompanying condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States ("GAAP") for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete consolidated financial statements. In the opinion of management, the financial statements reflect all adjustments necessary for fair presentation of results for the interim period. All such adjustments are of a normal, recurring nature.
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 condensed consolidated financial statements and related disclosures. These estimates are based on information available as of the date of the condensed consolidated financial statements. The Company believes that the estimates used in the preparation of the condensed consolidated financial statements are reasonable. Actual results could differ from these estimates.

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2019
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): September 30, December 31, Certificates of deposit (1) $ 1,000 $ — Total other short-term investments $ 1,000 $ — U.S. Treasury securities (2) $ 9,930 $ 2,586 Residential mortgage-backed securities - Agency (3) 719 784 Total investment securities $ 10,649 $ 3,370 (1) Includes certificates of deposit with maturity dates greater than 90 days but less than one year at the time of acquisition. (2) Includes $86 million and $42 million of U.S. Treasury securities pledged as swap collateral as of September 30, 2019 and December 31, 2018 , 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 Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value At September 30, 2019 Available-for-Sale Investment Securities (1) U.S. Treasury securities $ 9,758 $ 177 $ (5 ) $ 9,930 Residential mortgage-backed securities - Agency 449 2 (1 ) 450 Total available-for-sale investment securities $ 10,207 $ 179 $ (6 ) $ 10,380 Held-to-Maturity Investment Securities (2) Residential mortgage-backed securities - Agency (3) $ 269 $ 4 $ — $ 273 Total held-to-maturity investment securities $ 269 $ 4 $ — $ 273 At December 31, 2018 Available-for-Sale Investment Securities (1) U.S. Treasury securities $ 2,559 $ 27 $ — $ 2,586 Residential mortgage-backed securities - Agency 559 — (12 ) 547 Total available-for-sale investment securities $ 3,118 $ 27 $ (12 ) $ 3,133 Held-to-Maturity Investment Securities (2) Residential mortgage-backed securities - Agency (3) $ 237 $ — $ (4 ) $ 233 Total held-to-maturity investment securities $ 237 $ — $ (4 ) $ 233 (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 12 Months and More Than 12 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 Value Unrealized Losses Fair Value Unrealized Losses At September 30, 2019 Available-for-Sale Investment Securities U.S. Treasury securities 13 $ 1,660 $ (5 ) $ — $ — Residential mortgage-backed securities - Agency 11 $ 70 $ — $ 78 $ (1 ) Held-to-Maturity Investment Securities Residential mortgage-backed securities - Agency 22 $ 8 $ — $ 20 $ — At December 31, 2018 Available-for-Sale Investment Securities Residential mortgage-backed securities - Agency 31 $ 110 $ (1 ) $ 437 $ (11 ) Held-to-Maturity Investment Securities Residential mortgage-backed securities - Agency 90 $ 101 $ (1 ) $ 83 $ (3 )
Schedule of Maturities of Available-for-Sale Debt Securities and Held-to-Maturity Debt Securities	Maturities of available-for-sale debt securities and held-to-maturity debt securities are provided in the following table (dollars in millions): At September 30, 2019 One Year or Less After One Year Through Five Years After Five Years Through Ten Years After Ten Years Total Available-for-Sale Investment Securities—Amortized Cost U.S. Treasury securities $ 621 $ 7,980 $ 1,157 $ — $ 9,758 Residential mortgage-backed securities - Agency (1) — 97 352 — 449 Total available-for-sale investment securities $ 621 $ 8,077 $ 1,509 $ — $ 10,207 Held-to-Maturity Investment Securities—Amortized Cost Residential mortgage-backed securities - Agency (1) $ — $ — $ — $ 269 $ 269 Total held-to-maturity investment securities $ — $ — $ — $ 269 $ 269 Available-for-Sale Investment Securities—Fair Values U.S. Treasury securities $ 624 $ 8,137 $ 1,169 $ — $ 9,930 Residential mortgage-backed securities - Agency (1) — 97 353 — 450 Total available-for-sale investment securities $ 624 $ 8,234 $ 1,522 $ — $ 10,380 Held-to-Maturity Investment Securities—Fair Values Residential mortgage-backed securities - Agency (1) $ — $ — $ — $ 273 $ 273 Total held-to-maturity investment securities $ — $ — $ — $ 273 $ 273 (1) Maturities of residential mortgage-backed securities are reflective of the contractual maturities of the investment.

Loan Receivables (Tables)

Loan Receivables (Tables)	9 Months Ended
	Sep. 30, 2019
Loans and Leases Receivable Disclosure [Abstract]
Schedule of Loan Receivables	The Company's classes of receivables within the three portfolio segments are depicted in the following table (dollars in millions): September 30, December 31, Credit card loans (1) $ 73,968 $ 72,876 Other loans Personal loans 7,596 7,454 Private student loans 8,395 7,728 Other 1,193 817 Total other loans 17,184 15,999 PCI loans (2) 1,341 1,637 Total loan receivables 92,493 90,512 Allowance for loan losses (3,299 ) (3,041 ) Net loan receivables $ 89,194 $ 87,471 (1) Amounts include carrying values of $17.3 billion and $22.0 billion underlying investors' interest in trust debt at September 30, 2019 and December 31, 2018 , respectively, and $13.6 billion and $11.1 billion in seller's interest at September 30, 2019 and December 31, 2018 , respectively. See Note 4: Credit Card and Student Loan Securitization Activities for additional information. (2) Amounts include carrying values of $310 million and $363 million in loans pledged as collateral against the note issued from The Student Loan Corporation ("SLC") securitization trust at September 30, 2019 and December 31, 2018 , respectively. See Note 4: Credit Card and Student Loan Securitization Activities for additional information.
Schedule of Delinquent and Non-Accruing Loans	Information related to the delinquent and non-accruing loans in the Company's loan portfolio is shown below by each class of loan receivables except for PCI student loans, which is shown under the heading "— Purchased Credit-Impaired Loans" (dollars in millions): 30-89 Days Delinquent 90 or More Days Delinquent Total Past Due 90 or More Days Delinquent and Accruing Total Non-accruing (1) At September 30, 2019 Credit card loans (2) $ 950 $ 897 $ 1,847 $ 809 $ 269 Other loans Personal loans (3) 79 34 113 32 12 Private student loans (excluding PCI) (4) 114 36 150 35 9 Other 3 1 4 — 14 Total other loans (excluding PCI) 196 71 267 67 35 Total loan receivables (excluding PCI) $ 1,146 $ 968 $ 2,114 $ 876 $ 304 At December 31, 2018 Credit card loans (2) $ 885 $ 887 $ 1,772 $ 781 $ 266 Other loans Personal loans (3) 84 35 119 33 11 Private student loans (excluding PCI) (4) 117 38 155 37 8 Other 2 1 3 — 17 Total other loans (excluding PCI) 203 74 277 70 36 Total loan receivables (excluding PCI) $ 1,088 $ 961 $ 2,049 $ 851 $ 302 (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 $12 million and $9 million for the three months ended September 30, 2019 and 2018 , respectively, and $34 million and $28 million for the nine months ended September 30, 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) Credit card loans that are 90 or more days delinquent and accruing interest include $148 million and $116 million of loans accounted for as TDRs at September 30, 2019 and December 31, 2018 , respectively. (3) Personal loans that are 90 or more days delinquent and accruing interest include $8 million and $5 million of loans accounted for as TDRs at September 30, 2019 and December 31, 2018 , respectively. (4) Private student loans that are 90 or more days delinquent and accruing interest include $9 million and $7 million of loans accounted for as TDRs at September 30, 2019 and December 31, 2018 , respectively.
Schedule of Net Charge-offs	Information related to the net charge-offs in the Company's loan portfolio is shown below by each class of loan receivables except for PCI student loans, which is shown under the heading "— Purchased Credit-Impaired Loans" (dollars in millions): For the Three Months Ended September 30, 2019 2018 Net Net Charge-off (1) Net Net Charge-off (1) Credit card loans $ 611 3.32 % $ 543 3.14 % Other loans Personal loans 76 3.99 % 77 4.09 % Private student loans (excluding PCI) 14 0.69 % 22 1.19 % Other 1 — % — — % Total other loans 91 2.13 % 99 2.54 % Net charge-offs (excluding PCI) $ 702 3.09 % $ 642 3.03 % Net charge-offs (including PCI) $ 702 3.05 % $ 642 2.97 % For the Nine Months Ended September 30, 2019 2018 Net Net Charge-off (1) Net Net Charge-off (1) Credit card loans $ 1,850 3.43 % $ 1,638 3.27 % Other loans Personal loans 240 4.28 % 222 4.03 % Private student loans (excluding PCI) 44 0.73 % 65 1.17 % Other 1 — % 1 0.13 % Total other loans 285 2.30 % 288 2.52 % Net charge-offs (excluding PCI) $ 2,135 3.22 % $ 1,926 3.13 % Net charge-offs (including PCI) $ 2,135 3.17 % $ 1,926 3.06 % (1) Net charge-off rate represents net charge-off dollars (annualized) divided by average loans for the reporting period.
Schedule of Credit Risk Profile by FICO Score	The following table provides the most recent FICO scores available for the Company’s customers as a percentage of each class of loan receivables: Credit Risk Profile 660 and Above Less than 660 or No Score At September 30, 2019 Credit card loans 81 % 19 % Personal loans 94 % 6 % Private student loans (excluding PCI) (1) 95 % 5 % At December 31, 2018 Credit card loans 81 % 19 % Personal loans 94 % 6 % Private student loans (excluding PCI) (1) 94 % 6 % (1)
Schedule of Changes in the Allowance for Loan Losses	The following tables provide changes in the Company's allowance for loan losses (dollars in millions): For the Three Months Ended September 30, 2019 Credit Card Personal Loans Student Loans (1) Other Total Balance at beginning of period $ 2,691 $ 338 $ 167 $ 6 $ 3,202 Additions Provision for loan losses 719 86 (6 ) — 799 Deductions Charge-offs (784 ) (89 ) (17 ) (1 ) (891 ) Recoveries 173 13 3 — 189 Net charge-offs (611 ) (76 ) (14 ) (1 ) (702 ) Balance at end of period $ 2,799 $ 348 $ 147 $ 5 $ 3,299 For the Three Months Ended September 30, 2018 Credit Card Personal Loans Student Loans (1) Other Total Balance at beginning of period $ 2,334 $ 313 $ 170 $ 11 $ 2,828 Additions Provision for loan losses 633 87 22 — 742 Deductions Charge-offs (674 ) (86 ) (25 ) — (785 ) Recoveries 131 9 3 — 143 Net charge-offs (543 ) (77 ) (22 ) — (642 ) Other (2) — — (1 ) — (1 ) Balance at end of period $ 2,424 $ 323 $ 169 $ 11 $ 2,927 (1) Includes both PCI and non-PCI private student loans. (2) Net change in reserves on PCI pools having no remaining non-accretable difference. The following tables provide changes in the Company's allowance for loan losses (dollars in millions): For the Nine Months Ended September 30, 2019 Credit Card Personal Loans Student Loans (1) Other Total Balance at beginning of period $ 2,528 $ 338 $ 169 $ 6 $ 3,041 Additions Provision for loan losses 2,121 250 24 — 2,395 Deductions Charge-offs (2,347 ) (274 ) (54 ) (1 ) (2,676 ) Recoveries 497 34 10 — 541 Net charge-offs (1,850 ) (240 ) (44 ) (1 ) (2,135 ) Other (2) — — (2 ) — (2 ) Balance at end of period $ 2,799 $ 348 $ 147 $ 5 $ 3,299 For the Nine Months Ended September 30, 2018 Credit Card Personal Loans Student Loans (1) Other Total Balance at beginning of period $ 2,147 $ 301 $ 162 $ 11 $ 2,621 Additions Provision for loan losses 1,915 244 75 1 2,235 Deductions Charge-offs (2,021 ) (247 ) (74 ) (1 ) (2,343 ) Recoveries 383 25 9 — 417 Net charge-offs (1,638 ) (222 ) (65 ) (1 ) (1,926 ) Other (2) — — (3 ) — (3 ) Balance at end of period $ 2,424 $ 323 $ 169 $ 11 $ 2,927 (1) Includes both PCI and non-PCI private student loans. (2) Net change in reserves on PCI pools having no remaining non-accretable difference.
Schedule of Net Charge-offs of Interest and Fee Revenues on Loan Receivables	Net charge-offs of principal are recorded against the allowance for loan 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 Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Interest and fees accrued subsequently charged off, net of recoveries (recorded as a reduction of interest income) $ 127 $ 109 $ 382 $ 328 Fees accrued subsequently charged off, net of recoveries (recorded as a reduction to other income) $ 29 $ 26 $ 90 $ 81
Schedule of Allowance for Loan Losses and Recorded Investment in its Loan Portfolio by Impairment Methodology	The following tables provide additional detail of the Company's allowance for loan losses and recorded investment in its loan portfolio by impairment methodology (dollars in millions): Credit Card Personal Loans Student Loans (1) Other Loans Total At September 30, 2019 Allowance for loans evaluated for impairment as Collectively evaluated for impairment in accordance with ASC 450-20 $ 2,297 $ 287 $ 95 $ 4 $ 2,683 Evaluated for impairment in accordance with ASC 310-10-35 (2)(3) 502 61 29 1 593 Acquired with deteriorated credit quality, evaluated in accordance with ASC 310-30 — — 23 — 23 Total allowance for loan losses $ 2,799 $ 348 $ 147 $ 5 $ 3,299 Recorded investment in loans evaluated for impairment as Collectively evaluated for impairment in accordance with ASC 450-20 $ 70,860 $ 7,401 $ 8,146 $ 1,141 $ 87,548 Evaluated for impairment in accordance with ASC 310-10-35 (2)(3) 3,108 195 249 52 3,604 Acquired with deteriorated credit quality, evaluated in accordance with ASC 310-30 — — 1,341 — 1,341 Total recorded investment $ 73,968 $ 7,596 $ 9,736 $ 1,193 $ 92,493 At December 31, 2018 Allowance for loans evaluated for impairment as Collectively evaluated for impairment in accordance with ASC 450-20 $ 2,229 $ 292 $ 121 $ 4 $ 2,646 Evaluated for impairment in accordance with ASC 310-10-35 (2)(3) 299 46 23 2 370 Acquired with deteriorated credit quality, evaluated in accordance with ASC 310-30 — — 25 — 25 Total allowance for loan losses $ 2,528 $ 338 $ 169 $ 6 $ 3,041 Recorded investment in loans evaluated for impairment as Collectively evaluated for impairment in accordance with ASC 450-20 $ 70,628 $ 7,302 $ 7,546 $ 761 $ 86,237 Evaluated for impairment in accordance with ASC 310-10-35 (2)(3) 2,248 152 182 56 2,638 Acquired with deteriorated credit quality, evaluated in accordance with ASC 310-30 — — 1,637 — 1,637 Total recorded investment $ 72,876 $ 7,454 $ 9,365 $ 817 $ 90,512 (1) Includes both PCI and non-PCI private student loans. (2) Loan receivables evaluated for impairment in accordance with Accounting Standards Codification ("ASC") 310-10-35 include credit card loans, personal loans and student loans collectively evaluated for impairment in accordance with ASC Subtopic 310-40, Receivables, which consists of modified loans accounted for as TDRs. Other loans are individually evaluated for impairment and generally do not represent TDRs. (3) The unpaid principal balance of credit card loans was $2.8 billion and $2.0 billion at September 30, 2019 and December 31, 2018 , respectively. All loans accounted for as TDRs have a related allowance for loan losses.
Schedule of Troubled Debt Restructurings	Additional information about modified loans classified as TDRs is shown below (dollars in millions): Average recorded investment in loans Interest income recognized during period loans were impaired (1) Gross interest income that would have been recorded with original terms (2) For the Three Months Ended September 30, 2019 Credit card loans (3) $ 2,960 $ 93 $ 53 Personal loans $ 188 $ 5 $ 3 Private student loans $ 239 $ 5 $ 1 For the Three Months Ended September 30, 2018 Credit card loans (3) $ 1,815 $ 48 $ 37 Personal loans $ 134 $ 4 $ 1 Private student loans $ 166 $ 3 $ — For the Nine Months Ended September 30, 2019 Credit card loans (3) $ 2,682 $ 245 $ 148 Personal loans $ 174 $ 13 $ 7 Private student loans $ 215 $ 13 $ 1 For the Nine Months Ended September 30, 2018 Credit card loans (3) $ 1,612 $ 123 $ 95 Personal loans $ 125 $ 10 $ 4 Private student loans $ 152 $ 9 $ — (1) The Company does not separately track interest income on loans in modification programs. Amounts shown are estimated by applying an average interest rate to the average loans in the various modification programs. (2) The Company does not separately track the amount of additional gross interest income that would have been recorded if the loans in modification programs had not been restructured and interest had instead been recorded in accordance with the original terms. Amounts shown are estimated by applying the difference between the average interest rate earned on non-impaired loans and the average interest rate earned on loans in the modification programs to the average loans in the modification programs. (3) Includes credit card loans that were modified in TDRs, but are no longer enrolled in a TDR program due to noncompliance with the terms of the modification or due to successful completion of a program after which charging privileges may be reinstated based on customer-level evaluation. The average balance of credit card loans that were no longer enrolled in a TDR program was $985 million and $427 million for the three months ended September 30, 2019 and 2018 , respectively, and $833 million and $404 million for the nine months ended September 30, 2019 and 2018 , respectively.
Schedule of Loans That Entered a Modification Program During the Period	The following table provides information on loans that entered a loan modification program during the period (dollars in millions): For the Three Months Ended September 30, 2019 2018 Number of Accounts Balances Number of Accounts Balances Accounts that entered a loan modification program during the period Credit card loans 97,046 $ 623 69,127 $ 444 Personal loans 2,859 $ 39 1,903 $ 27 Private student loans 1,692 $ 31 935 $ 17 For the Nine Months Ended September 30, 2019 2018 Number of Accounts Balances Number of Accounts Balances Accounts that entered a loan modification program during the period Credit card loans 273,970 $ 1,766 185,185 $ 1,187 Personal loans 8,129 $ 110 5,867 $ 79 Private student loans 4,978 $ 92 2,887 $ 54
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 Three Months Ended September 30, 2019 2018 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) 19,108 $ 109 10,535 $ 60 Personal loans (2) 1,131 $ 15 847 $ 11 Private student loans (3) 396 $ 8 278 $ 5 For the Nine Months Ended September 30, 2019 2018 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) 50,980 $ 294 28,319 $ 156 Personal loans (2) 2,925 $ 42 2,059 $ 27 Private student loans (3) 966 $ 19 753 $ 13 (1) Terms revert back to the pre-modification terms for customers who default from a temporary program and charging privileges remain revoked in most cases. (2) For credit card loans and personal loans, a customer defaults from a modification program after two consecutive missed payments. 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
Schedule of Changes in Accretable Yield for the Acquired Loans	The following table provides changes in accretable yield for the acquired loans during each period (dollars in millions): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Balance at beginning of period $ 508 $ 608 $ 548 $ 669 Accretion into interest income (29 ) (34 ) (92 ) (106 ) Other changes in expected cash flows — 1 23 12 Balance at end of period $ 479 $ 575 $ 479 $ 575

Credit Card and Student Loan _2

Credit Card and Student Loan Securitization Activities (Tables)	9 Months Ended
	Sep. 30, 2019
Variable Interest Entities Disclosure [Abstract]
Schedule of Restricted Credit Card Securitized Assets [Text Block]	The carrying values of these restricted assets, which are presented on the Company's condensed consolidated statements of financial condition as relating to securitization activities, are shown in the following table (dollars in millions): September 30, December 31, Restricted cash $ 26 $ 1,834 Investors' interests held by third-party investors 12,600 16,800 Investors' interests held by wholly-owned subsidiaries of Discover Bank 4,657 5,211 Seller's interest 13,578 11,050 Loan receivables (1) 30,835 33,061 Allowance for loan losses allocated to securitized loan receivables (1) (1,167 ) (1,150 ) Net loan receivables 29,668 31,911 Other 6 7 Carrying value of assets of consolidated variable interest entities $ 29,700 $ 33,752 (1) The Company maintains its allowance for loan losses at an amount sufficient to absorb probable losses inherent in 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.
Schedule of Restricted Student Loan Securitized Assets [Text Block]	The carrying values of these restricted assets, which are presented on the Company's condensed consolidated statements of financial condition as relating to securitization activities, are shown in the following table (dollars in millions): September 30, December 31, Restricted cash $ 11 $ 12 Student loan receivables 310 363 Carrying value of assets of consolidated variable interest entities $ 321 $ 375

Deposits (Tables)

Deposits (Tables)	9 Months Ended
	Sep. 30, 2019
Deposits [Abstract]
Schedule of Interest Bearing Deposit Accounts	The following table provides a summary of interest-bearing deposit accounts (dollars in millions): September 30, December 31, Certificates of deposit in amounts less than $100,000 $ 25,248 $ 27,947 Certificates of deposit in amounts $100,000 or greater (1) 8,736 6,841 Savings deposits, including money market deposit accounts 36,343 32,296 Total interest-bearing deposits $ 70,327 $ 67,084 (1) Includes $2.4 billion and $1.7 billion in certificates of deposit equal to or greater than $250,000, the Federal Deposit Insurance Corporation ("FDIC") insurance limit, as of September 30, 2019 and December 31, 2018 , respectively.
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): September 30, 2019 Three months or less $ 1,370 Over three months through six months 1,502 Over six months through twelve months 3,311 Over twelve months 2,553 Total $ 8,736
Schedule of Certificates of Deposit Maturities	The following table summarizes certificates of deposit maturing over the remainder of this year, over each of the next four years, and thereafter (dollars in millions): September 30, 2019 2019 $ 4,122 2020 15,328 2021 6,382 2022 3,178 2023 1,896 Thereafter 3,078 Total $ 33,984

Long-Term Borrowings (Tables)

Long-Term Borrowings (Tables)	9 Months Ended
	Sep. 30, 2019
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): September 30, 2019 December 31, 2018 Maturity Interest Weighted-Average Interest Rate Outstanding Amount Outstanding Amount Securitized Debt Fixed-rate asset-backed securities (1) 2020-2024 1.39%-3.32% 2.58% $ 7,637 $ 10,657 Floating-rate asset-backed securities (2)(3) 2020-2024 2.26%-2.63% 2.41% 5,014 6,063 Total Discover Card Master Trust I and Discover Card Execution Note Trust 12,651 16,720 Floating-rate asset-backed security (4)(5) 2031 6.00% 6.00% 169 197 Total SLC Private Student Loan Trust 169 197 Total long-term borrowings - owed to securitization investors 12,820 16,917 Discover Financial Services (Parent Company) Fixed-rate senior notes 2022-2027 3.75%-5.20% 4.16% 3,287 2,743 Fixed-rate retail notes 2019-2031 2.85%-4.60% 3.73% 339 346 Discover Bank Fixed-rate senior bank notes (1) 2020-2028 2.45%-4.65% 3.55% 6,811 6,027 Fixed-rate subordinated bank notes 2019-2028 4.68%-8.70% 6.32% 1,197 1,195 Total long-term borrowings $ 24,454 $ 27,228 (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 14: 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 September 30, 2019 . (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 14: Derivatives and Hedging Activities. (4) SLC Private Student Loan Trust floating-rate asset-backed security includes an issuance with the following interest rate term: Prime rate + 100 basis points as of September 30, 2019 . (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 the remainder of this year, over each of the next four years, and thereafter (dollars in millions): September 30, 2019 2019 $ 200 2020 4,745 2021 4,218 2022 4,124 2023 3,329 Thereafter 7,838 Total $ 24,454

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Changes in Accumulated Other Comprehensive Income (Loss)	Changes in each component of accumulated other comprehensive income (loss) ("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 Three Months Ended September 30, 2019 Balance at June 30, 2019 $ 112 $ (8 ) $ (187 ) $ (83 ) Net change 17 (8 ) — 9 Balance at September 30, 2019 $ 129 $ (16 ) $ (187 ) $ (74 ) For the Three Months Ended September 30, 2018 Balance at June 30, 2018 $ (14 ) $ 39 $ (187 ) $ (162 ) Net change (2 ) 4 — 2 Balance at September 30, 2018 $ (16 ) $ 43 $ (187 ) $ (160 ) For the Nine Months Ended September 30, 2019 Balance at December 31, 2018 $ 10 $ 22 $ (188 ) $ (156 ) Net change 119 (38 ) 1 82 Balance at September 30, 2019 $ 129 $ (16 ) $ (187 ) $ (74 ) For the Nine Months Ended September 30, 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 (10 ) 30 1 21 Balance at September 30, 2018 $ (16 ) $ 43 $ (187 ) $ (160 ) (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 other comprehensive income (loss) ("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 Three Months Ended September 30, 2019 Available-for-Sale Investment Securities Net unrealized holding gains arising during the period $ 24 $ (7 ) $ 17 Net change $ 24 $ (7 ) $ 17 Cash Flow Hedges Net unrealized losses arising during the period $ (9 ) $ 2 $ (7 ) Amounts reclassified from AOCI (2 ) 1 (1 ) Net change $ (11 ) $ 3 $ (8 ) For the Three Months Ended September 30, 2018 Available-for-Sale Investment Securities Net unrealized holding losses arising during the period $ (4 ) $ 2 $ (2 ) Net change $ (4 ) $ 2 $ (2 ) Cash Flow Hedges Net unrealized gains arising during the period $ 8 $ (2 ) $ 6 Amounts reclassified from AOCI (2 ) — (2 ) Net change $ 6 $ (2 ) $ 4 For the Nine Months Ended September 30, 2019 Available-for-Sale Investment Securities Net unrealized holding gains arising during the period $ 158 $ (39 ) $ 119 Net change $ 158 $ (39 ) $ 119 Cash Flow Hedges Net unrealized losses arising during the period $ (44 ) $ 11 $ (33 ) Amounts reclassified from AOCI (7 ) 2 (5 ) Net change $ (51 ) $ 13 $ (38 ) Pension Plan Unrealized gains arising during the period $ 1 $ — $ 1 Net change $ 1 $ — $ 1 For the Nine Months Ended September 30, 2018 Available-for-Sale Investment Securities Net unrealized holding losses arising during the period $ (14 ) $ 4 $ (10 ) Net change $ (14 ) $ 4 $ (10 ) Cash Flow Hedges Net unrealized gains arising during the period $ 42 $ (10 ) $ 32 Amounts reclassified from AOCI (2 ) — (2 ) Net change $ 40 $ (10 ) $ 30 Pension Plan Unrealized gains arising during the period $ 1 $ — $ 1 Net change $ 1 $ — $ 1

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Calculation	The following table presents the calculation of the Company's effective income tax rate (dollars in millions, except effective income tax rate): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Income before income tax expense $ 994 $ 967 $ 2,911 $ 2,700 Income tax expense $ 224 $ 247 $ 662 $ 645 Effective income tax rate 22.5 % 25.5 % 22.7 % 23.9 %

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Schedule of Basic and Diluted EPS	The following table presents the calculation of basic and diluted earnings per share ("EPS") (in millions, except per share amounts): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Numerator Net income $ 770 $ 720 $ 2,249 $ 2,055 Preferred stock dividends (15 ) (15 ) (31 ) (31 ) Net income available to common stockholders 755 705 2,218 2,024 Income allocated to participating securities (6 ) (6 ) (15 ) (16 ) Net income allocated to common stockholders $ 749 $ 699 $ 2,203 $ 2,008 Denominator Weighted-average shares of common stock outstanding 317 341 323 348 Effect of dilutive common stock equivalents — 1 — — Weighted-average shares of common stock outstanding and common stock equivalents 317 342 323 348 Basic earnings per common share $ 2.36 $ 2.05 $ 6.83 $ 5.77 Diluted earnings per common share $ 2.36 $ 2.05 $ 6.82 $ 5.77

Capital Adequacy (Tables)

Capital Adequacy (Tables)	9 Months Ended
	Sep. 30, 2019
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 Requirements Capital Requirements To Be Classified as Well-Capitalized Amount Ratio (1) Amount Ratio Amount (2) Ratio (2) September 30, 2019 Total capital (to risk-weighted assets) Discover Financial Services $ 13,009 13.7 % $ 7,598 ≥8.0% $ 9,498 ≥10.0% Discover Bank $ 13,354 14.2 % $ 7,515 ≥8.0% $ 9,394 ≥10.0% Tier 1 capital (to risk-weighted assets) Discover Financial Services $ 11,403 12.0 % $ 5,699 ≥6.0% $ 5,699 ≥6.0% Discover Bank $ 11,157 11.9 % $ 5,637 ≥6.0% $ 7,515 ≥8.0% Tier 1 capital (to average assets) Discover Financial Services $ 11,403 10.3 % $ 4,409 ≥4.0% N/A N/A Discover Bank $ 11,157 10.2 % $ 4,362 ≥4.0% $ 5,452 ≥5.0% Common Equity Tier 1 (to risk-weighted assets) Discover Financial Services $ 10,840 11.4 % $ 4,274 ≥4.5% N/A N/A Discover Bank $ 11,157 11.9 % $ 4,227 ≥4.5% $ 6,106 ≥6.5% December 31, 2018 Total capital (to risk-weighted assets) Discover Financial Services $ 12,532 13.5 % $ 7,450 ≥8.0% $ 9,312 ≥10.0% Discover Bank $ 13,106 14.2 % $ 7,372 ≥8.0% $ 9,215 ≥10.0% Tier 1 capital (to risk-weighted assets) Discover Financial Services $ 10,895 11.7 % $ 5,587 ≥6.0% $ 5,587 ≥6.0% Discover Bank $ 10,834 11.8 % $ 5,529 ≥6.0% $ 7,372 ≥8.0% Tier 1 capital (to average assets) Discover Financial Services $ 10,895 10.1 % $ 4,308 ≥4.0% N/A N/A Discover Bank $ 10,834 10.2 % $ 4,265 ≥4.0% $ 5,332 ≥5.0% Common Equity Tier 1 (to risk-weighted assets) Discover Financial Services $ 10,332 11.1 % $ 4,191 ≥4.5% N/A N/A Discover Bank $ 10,834 11.8 % $ 4,147 ≥4.5% $ 5,990 ≥6.5% (1) Capital ratios are calculated based on the Basel III Standardized Approach rules, subject to applicable 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)	9 Months Ended
	Sep. 30, 2019
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 (in millions): For the Three Months Ended September 30, For the Nine Months Ended September 30, 2019 2018 2019 2018 Aggregate sales transaction volume (1) $ 44,332 $ 40,806 $ 125,922 $ 116,800 (1) Represents period 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)	9 Months Ended
	Sep. 30, 2019
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 for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Balance at September 30, 2019 Assets Fair value - OCI U.S. Treasury securities $ 9,930 $ — $ — $ 9,930 Residential mortgage-backed securities - Agency — 450 — 450 Available-for-sale investment securities $ 9,930 $ 450 $ — $ 10,380 Liabilities Fair value - OCI Derivative financial instruments - cash flow hedges (1) $ — $ 3 $ — $ 3 Fair value - Net income Derivative financial instruments - fair value hedges (1) $ — $ 1 $ — $ 1 Balance at December 31, 2018 Assets Fair value - OCI U.S. Treasury securities $ 2,586 $ — $ — $ 2,586 Residential mortgage-backed securities - Agency — 547 — 547 Available-for-sale investment securities $ 2,586 $ 547 $ — $ 3,133 Derivative financial instruments - cash flow hedges (1) $ — $ 8 $ — $ 8 Fair value - Net income Derivative financial instruments - fair value hedges (1) $ — $ 5 $ — $ 5 Liabilities Fair value - OCI Derivative financial instruments - cash flow hedges (1) $ — $ 2 $ — $ 2 (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 condensed 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 September 30, 2019 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Carrying Value Assets Amortized cost Residential mortgage-backed securities - Agency $ — $ 273 $ — $ 273 $ 269 Held-to-maturity investment securities $ — $ 273 $ — $ 273 $ 269 Net loan receivables $ — $ — $ 92,855 $ 92,855 $ 89,194 Carrying value approximates fair value (1) Cash and cash equivalents $ 6,075 $ — $ — $ 6,075 $ 6,075 Restricted cash $ 37 $ — $ — $ 37 $ 37 Other short-term investments $ 1,000 $ — $ — $ 1,000 $ 1,000 Accrued interest receivables (2) $ — $ 1,054 $ — $ 1,054 $ 1,054 Liabilities Amortized cost Time deposits (3) $ — $ 34,478 $ — $ 34,478 $ 33,984 Long-term borrowings - owed to securitization investors $ — $ 12,729 $ 185 $ 12,914 $ 12,820 Other long-term borrowings — 12,348 — 12,348 11,634 Long-term borrowings $ — $ 25,077 $ 185 $ 25,262 $ 24,454 Carrying value approximates fair value (1) Accrued interest payables (2) $ — $ 243 $ — $ 243 $ 243 (1) The carrying values of these assets and liabilities approximate fair value due to the nature of their liquidity (i.e., due or payable in less than one year). (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 condensed consolidated statements of financial condition. (3) Excludes deposits without contractually defined maturities for all periods presented. 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, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Total Carrying Value Assets Amortized cost Residential mortgage-backed securities - Agency $ — $ 233 $ — $ 233 $ 237 Held-to-maturity investment securities $ — $ 233 $ — $ 233 $ 237 Net loan receivables $ — $ — $ 90,787 $ 90,787 $ 87,471 Carrying value approximates fair value (1) Cash and cash equivalents $ 13,299 $ — $ — $ 13,299 $ 13,299 Restricted cash $ 1,846 $ — $ — $ 1,846 $ 1,846 Accrued interest receivables (2) $ — $ 951 $ — $ 951 $ 951 Liabilities Amortized cost Time deposits (3) $ — $ 34,635 $ — $ 34,635 $ 34,788 Long-term borrowings - owed to securitization investors $ — $ 16,701 $ 217 $ 16,918 $ 16,917 Other long-term borrowings — 10,325 — 10,325 10,311 Long-term borrowings $ — $ 27,026 $ 217 $ 27,243 $ 27,228 Carrying value approximates fair value (1) Accrued interest payables (2) $ — $ 292 $ — $ 292 $ 292 (1) The carrying values of these assets and liabilities approximate fair value due to the nature of their liquidity (i.e., due or payable in less than one year). (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 condensed 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)	9 Months Ended
	Sep. 30, 2019
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): September 30, 2019 December 31, 2018 Notional Amount Number of Outstanding Derivative Contracts Derivative Assets Derivative Liabilities Notional Amount Derivative Assets Derivative Liabilities Derivatives designated as hedges Interest rate swaps—cash flow hedge $ 1,650 4 $ — $ 3 $ 2,450 $ 8 $ 2 Interest rate swaps—fair value hedge $ 9,000 12 — 1 $ 8,000 5 — Derivatives not designated as hedges Foreign exchange forward contracts (1) $ 34 7 — — $ 33 — — Total gross derivative assets/liabilities (2) — 4 13 2 Less: collateral held/posted (3) — (4 ) (8 ) (2 ) Total net derivative assets/liabilities $ — $ — $ 5 $ — (1) The foreign exchange forward contracts have notional amounts of EUR 9 million , GBP 12 million , SGD 1 million and INR 596 million as of September 30, 2019 and notional amounts of EUR 9 million , GBP 12 million , SGD 1 million and INR 464 million as of December 31, 2018 . (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 September 30, 2019 , the Company had one outstanding contract with a notional amount of $27 million and immaterial fair value. At December 31, 2018 , the Company had one outstanding contract with a notional amount of $79 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 adjustment for fair value hedges (dollars in millions): September 30, 2019 December 31, 2018 Carrying Amount of Hedged Assets/Liabilities Cumulative Amount of Fair Value Hedging Adjustment Increasing (Decreasing) the Carrying Amount of Hedged Assets/Liabilities Carrying Amount of Hedged Assets/Liabilities Cumulative Amount of Fair Value Hedging Adjustment Increasing (Decreasing) the Carrying Amount of Hedged Assets/Liabilities Long-term borrowings $ 9,046 $ 69 $ 7,893 $ (91 )
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 condensed consolidated financial statements such impact is reported (dollars in millions): Location and Amount of (Losses) Gains Recognized in Income Interest (Expense) Deposits Long-Term Borrowings Other Income For the Three Months Ended September 30, 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 $ (407 ) $ (231 ) $ 23 The effects of cash flow and fair value hedging Gains on cash flow hedging relationship Amounts reclassified from OCI into earnings $ 1 $ 1 $ — Gains (losses) on fair value hedging relationship Gains (losses) on hedged items $ — $ (20 ) $ — Gains on interest rate swaps — 12 — Total gains (losses) on fair value hedges $ — $ (8 ) $ — The effects of derivatives not designated in hedging relationships Gains on derivatives not designated as hedges $ — $ — $ 1 For the Three Months Ended September 30, 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 $ (329 ) $ (229 ) $ 20 The effects of cash flow and fair value hedging Gains on cash flow hedging relationship Amounts reclassified from OCI into earnings $ — $ 2 $ — Gains (losses) on fair value hedging relationship Gains on hedged items $ — $ 2 $ — Gains (losses) on interest rate swaps — (14 ) — Total gains (losses) on fair value hedges $ — $ (12 ) $ — The effects of derivatives not designated in hedging relationships Gains on derivatives not designated as hedges $ — $ — $ 1 The following table summarizes the impact of the derivative instruments on income and indicates where within the condensed consolidated financial statements such impact is reported (dollars in millions): Location and Amount of (Losses) Gains Recognized in Income Interest (Expense) Deposits Long-Term Borrowings Other Income For the Nine Months Ended September 30, 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 $ (1,194 ) $ (721 ) $ 73 The effects of cash flow and fair value hedging Gains on cash flow hedging relationship Amounts reclassified from OCI into earnings $ 3 $ 4 $ — Gains (losses) on fair value hedging relationship Gains (losses) on hedged items $ — $ (160 ) $ — Gains on interest rate swaps — 128 — Total gains (losses) on fair value hedges $ — $ (32 ) $ — The effects of derivatives not designated in hedging relationships Gains on derivatives not designated as hedges $ — $ — $ 1 For the Nine Months Ended September 30, 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 $ (878 ) $ (656 ) $ 73 The effects of cash flow and fair value hedging (Losses) gains on cash flow hedging relationship Amounts reclassified from OCI into earnings $ (1 ) $ 3 $ — Gains (losses) on fair value hedging relationship Gains on hedged items $ — $ 61 $ — Gains (losses) on interest rate swaps — (88 ) — Total gains (losses) on fair value hedges $ — $ (27 ) $ — The effects of derivatives not designated in hedging relationships Gains on derivatives not designated as hedges $ — $ — $ 2

Segment Disclosures (Tables)

Segment Disclosures (Tables)	9 Months Ended
	Sep. 30, 2019
Segment Reporting [Abstract]
Schedule of Segment Disclosures	The following table presents segment data (dollars in millions): Direct Banking Payment Services Total For the Three Months Ended September 30, 2019 Interest income Credit card loans $ 2,465 $ — $ 2,465 Private student loans 175 — 175 PCI student loans 29 — 29 Personal loans 249 — 249 Other 122 — 122 Total interest income 3,040 — 3,040 Interest expense 638 — 638 Net interest income 2,402 — 2,402 Provision for loan losses 799 — 799 Other income 409 89 498 Other expense 1,069 38 1,107 Income before income tax expense $ 943 $ 51 $ 994 For the Three Months Ended September 30, 2018 Interest income Credit card loans $ 2,258 $ — $ 2,258 Private student loans 154 — 154 PCI student loans 34 — 34 Personal loans 238 — 238 Other 97 — 97 Total interest income 2,781 — 2,781 Interest expense 558 — 558 Net interest income 2,223 — 2,223 Provision for loan losses 742 — 742 Other income 421 80 501 Other expense 979 36 1,015 Income before income tax expense $ 923 $ 44 $ 967 The following table presents segment data (dollars in millions): Direct Banking Payment Services Total For the Nine Months Ended September 30, 2019 Interest income Credit card loans $ 7,223 $ — $ 7,223 Private student loans 520 — 520 PCI student loans 92 — 92 Personal loans 727 — 727 Other 391 1 392 Total interest income 8,953 1 8,954 Interest expense 1,915 — 1,915 Net interest income 7,038 1 7,039 Provision for loan losses 2,395 — 2,395 Other income 1,217 259 1,476 Other expense 3,097 112 3,209 Income before income tax expense $ 2,763 $ 148 $ 2,911 For the Nine Months Ended September 30, 2018 Interest income Credit card loans $ 6,487 $ — $ 6,487 Private student loans 451 — 451 PCI student loans 106 — 106 Personal loans 693 — 693 Other 249 — 249 Total interest income 7,986 — 7,986 Interest expense 1,534 — 1,534 Net interest income 6,452 — 6,452 Provision for loan losses 2,235 — 2,235 Other income 1,213 237 1,450 Other expense 2,859 108 2,967 Income before income tax expense $ 2,571 $ 129 $ 2,700

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	9 Months Ended
	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue [Table Text Block]	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): Direct Banking Payment Services Total For the Three Months Ended September 30, 2019 Other income subject to ASC 606 Discount and interchange revenue, net (1) $ 238 $ 17 $ 255 Protection products revenue 48 — 48 Transaction processing revenue — 52 52 Other income 3 20 23 Total other income subject to ASC 606 (2) 289 89 378 Other income not subject to ASC 606 Loan fee income 120 — 120 Total other income not subject to ASC 606 120 — 120 Total other income by operating segment $ 409 $ 89 $ 498 For the Three Months Ended September 30, 2018 Other income subject to ASC 606 Discount and interchange revenue, net (1) $ 266 $ 14 $ 280 Protection products revenue 51 — 51 Transaction processing revenue — 47 47 Other income 1 19 20 Total other income subject to ASC 606 (2) 318 80 398 Other income not subject to ASC 606 Loan fee income 103 — 103 Total other income not subject to ASC 606 103 — 103 Total other income by operating segment $ 421 $ 80 $ 501 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): Direct Banking Payment Services Total For the Nine Months Ended September 30, 2019 Other income subject to ASC 606 Discount and interchange revenue, net (1) $ 738 $ 47 $ 785 Protection products revenue 146 — 146 Transaction processing revenue — 146 146 Other income 7 66 73 Total other income subject to ASC 606 (2) 891 259 1,150 Other income not subject to ASC 606 Loan fee income 326 — 326 Total other income not subject to ASC 606 326 — 326 Total other income by operating segment $ 1,217 $ 259 $ 1,476 For the Nine Months Ended September 30, 2018 Other income subject to ASC 606 Discount and interchange revenue, net (1) $ 758 $ 39 $ 797 Protection products revenue 154 — 154 Transaction processing revenue — 132 132 Other income 7 66 73 Total other income subject to ASC 606 (2) 919 237 1,156 Other income not subject to ASC 606 Loan fee income 294 — 294 Total other income not subject to ASC 606 294 — 294 Total other income by operating segment $ 1,213 $ 237 $ 1,450 (1) Net of rewards, including Cashback Bonus rewards, of $520 million and $473 million for the three months ended September 30, 2019 and 2018 , respectively, and $1.4 billion and $1.3 billion for the nine months ended September 30, 2019 and 2018 , respectively. (2) Excludes $2 million of deposit product fees that are reported within net interest income for the nine months ended September 30, 2019 and 2018 and $1 million for the three months ended September 30, 2018 . Deposit product fees were immaterial for the three months ended September 30, 2019 .

Background and Basis of Prese_3

Background and Basis of Presentation (Narrative) (Details)	9 Months Ended
	Sep. 30, 2019segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of reportable segments (in number of segments)	2

Investments (Narrative) (Detail

Investments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Investment Holdings [Line Items]
Losses related to other-than-temporary impairments	$ 0	$ 0	$ 0	$ 0
Proceeds from sales of available-for-sale securities	0	0	0	0
Recognized gains (losses) on available-for-sale securities	0	$ 0	0	$ 0
Affordable housing project equity method investments	299		299		$ 271
Contingent liabilities related to affordable housing project equity method investments	57		57		30
Other Assets [Member] | Community Reinvestment Act [Member]
Investment Holdings [Line Items]
Equity method investments	321		321		295
Other Liabilities [Member] | Community Reinvestment Act [Member]
Investment Holdings [Line Items]
Contingent liabilities related to equity method investments	$ 57		$ 57		$ 49

Investments (Schedule of Invest

Investments (Schedule of Investment Securities) (Details) - USD ($) $ in Millions		Sep. 30, 2019	Dec. 31, 2018
Investment Holdings [Line Items]
Other short-term investments		$ 1,000	$ 0
Investment securities		10,649	3,370
U.S. Treasury Securities [Member]
Investment Holdings [Line Items]
Investment securities	[1]	9,930	2,586
Derivative collateral		86	42
Residential Mortgage-Backed Securities - Agency [Member]
Investment Holdings [Line Items]
Investment securities	[2]	719	784
Certificates of Deposit [Member]
Investment Holdings [Line Items]
Other short-term investments	[3]	$ 1,000	$ 0
[1]	Includes $86 million and $42 million of U.S. Treasury securities pledged as swap collateral as of September 30, 2019 and December 31, 2018
[2]	Consists of residential mortgage-backed securities issued by Fannie Mae, Freddie Mac and Ginnie Mae.
[3]	Includes certificates of deposit with maturity dates greater than 90 days but less than one year at the time of acquisition.

Investments (Schedule of Amorti

Investments (Schedule of Amortized Cost, Gross Unrealized Gains, Gross Unrealized Losses and Fair Value) (Details) - USD ($) $ in Millions		Sep. 30, 2019		Dec. 31, 2018
Investment Holdings [Line Items]
Available-for-sale investment securities, amortized cost	[1]	$ 10,207		$ 3,118
Available-for-sale investment securities, gross unrealized gains	[1]	179		27
Available-for-sale investment securities, gross unrealized losses	[1]	(6)		(12)
Available-for-sale investment securities, fair value	[1]	10,380		3,133
Held-to-maturity investment securities, amortized cost	[2]	269		237
Held-to-maturity investment securities, gross unrealized gains	[2]	4		0
Held-to-maturity investment securities, gross unrealized losses	[2]	0		(4)
Held-to-maturity investment securities, fair value	[2]	273		233
U.S. Treasury Securities [Member]
Investment Holdings [Line Items]
Available-for-sale investment securities, amortized cost	[1]	9,758		2,559
Available-for-sale investment securities, gross unrealized gains	[1]	177		27
Available-for-sale investment securities, gross unrealized losses	[1]	(5)		0
Available-for-sale investment securities, fair value	[1]	9,930		2,586
Residential Mortgage-Backed Securities - Agency [Member]
Investment Holdings [Line Items]
Available-for-sale investment securities, amortized cost	[1]	449	[3]	559
Available-for-sale investment securities, gross unrealized gains	[1]	2		0
Available-for-sale investment securities, gross unrealized losses	[1]	(1)		(12)
Available-for-sale investment securities, fair value	[1]	450	[3]	547
Held-to-maturity investment securities, amortized cost	[2],[4]	269	[3]	237
Held-to-maturity investment securities, gross unrealized gains	[2],[4]	4		0
Held-to-maturity investment securities, gross unrealized losses	[2],[4]	0		(4)
Held-to-maturity investment securities, fair value	[2],[4]	$ 273	[3]	$ 233
[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	Sep. 30, 2019USD ($)securities	Dec. 31, 2018USD ($)securities
U.S. Treasury Securities [Member]
Investment Holdings [Line Items]
Available-for-sale investment securities, continuous unrealized loss position, number of securities | securities	13
Available-for-sale investment securities, continuous unrealized loss position, less than 12 months, fair value	$ 1,660
Available-for-sale investment securities, continuous unrealized loss position, less than 12 months, unrealized losses	(5)
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]
Available-for-sale investment securities, continuous unrealized loss position, number of securities | securities	11	31
Available-for-sale investment securities, continuous unrealized loss position, less than 12 months, fair value	$ 70	$ 110
Available-for-sale investment securities, continuous unrealized loss position, less than 12 months, unrealized losses	0	(1)
Available-for-sale investment securities, continuous unrealized loss position, more than 12 months, fair value	78	437
Available-for-sale investment securities, continuous unrealized loss position, more than 12 months, unrealized losses	$ (1)	$ (11)
Held-to-maturity investment securities, continuous unrealized loss position, number of securities | securities	22	90
Held-to-maturity investment securities, continuous unrealized loss position, less than 12 months, fair value	$ 8	$ 101
Held-to-maturity investment securities, continuous unrealized loss position, less than 12 months, unrealized losses	0	(1)
Held-to-maturity investment securities, continuous unrealized loss position, more than 12 months, fair value	20	83
Held-to-maturity investment securities, continuous unrealized loss position, more than 12 months, unrealized losses	$ 0	$ (3)

Investments (Schedule of Maturi

Investments (Schedule of Maturities of Available-for-Sale Debt Securities and Held-to-Maturity Debt Securities) (Details) - USD ($) $ in Millions		Sep. 30, 2019		Dec. 31, 2018
Investment Holdings [Line Items]
Available-for-sale investment securities, debt maturities, one year or less, amortized cost		$ 621
Available-for-sale investment securities, debt maturities, after one year through five years, amortized cost		8,077
Available-for-sale investment securities, debt maturities, after five years through ten years, amortized cost		1,509
Available-for-sale investment securities, debt maturities, after ten years, amortized cost		0
Available-for-sale investment securities, amortized cost	[1]	10,207		$ 3,118
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		269
Held-to-maturity investment securities, amortized cost	[2]	269		237
Available-for-sale investment securities, debt maturities, one year or less, fair value		624
Available-for-sale investment securities, debt maturities, after one year through five years, fair value		8,234
Available-for-sale investment securities, debt maturities, after five years through ten years, fair value		1,522
Available-for-sale investment securities, debt maturities, after ten years, fair value		0
Available-for-sale investment securities, fair value	[1]	10,380		3,133
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		273
Held-to-maturity investment securities, fair value	[2]	273		233
U.S. Treasury Securities [Member]
Investment Holdings [Line Items]
Available-for-sale investment securities, debt maturities, one year or less, amortized cost		621
Available-for-sale investment securities, debt maturities, after one year through five years, amortized cost		7,980
Available-for-sale investment securities, debt maturities, after five years through ten years, amortized cost		1,157
Available-for-sale investment securities, debt maturities, after ten years, amortized cost		0
Available-for-sale investment securities, amortized cost	[1]	9,758		2,559
Available-for-sale investment securities, debt maturities, one year or less, fair value		624
Available-for-sale investment securities, debt maturities, after one year through five years, fair value		8,137
Available-for-sale investment securities, debt maturities, after five years through ten years, fair value		1,169
Available-for-sale investment securities, debt maturities, after ten years, fair value		0
Available-for-sale investment securities, fair value	[1]	9,930		2,586
Residential Mortgage-Backed Securities - Agency [Member]
Investment Holdings [Line Items]
Available-for-sale investment securities, debt maturities, one year or less, amortized cost	[3]	0
Available-for-sale investment securities, debt maturities, after one year through five years, amortized cost	[3]	97
Available-for-sale investment securities, debt maturities, after five years through ten years, amortized cost	[3]	352
Available-for-sale investment securities, debt maturities, after ten years, amortized cost	[3]	0
Available-for-sale investment securities, amortized cost	[1]	449	[3]	559
Held-to-maturity investment securities, debt maturities, one year or less, amortized cost	[3]	0
Held-to-maturity investment securities, debt maturities, after one year through five years, amortized cost	[3]	0
Held-to-maturity investment securities, debt maturities, after five years through ten years, amortized cost	[3]	0
Held-to-maturity investment securities, debt maturities, after ten years, amortized cost	[3]	269
Held-to-maturity investment securities, amortized cost	[2],[4]	269	[3]	237
Available-for-sale investment securities, debt maturities, one year or less, fair value	[3]	0
Available-for-sale investment securities, debt maturities, after one year through five years, fair value	[3]	97
Available-for-sale investment securities, debt maturities, after five years through ten years, fair value	[3]	353
Available-for-sale investment securities, debt maturities, after ten years, fair value	[3]	0
Available-for-sale investment securities, fair value	[1]	450	[3]	547
Held-to-maturity investment securities, debt maturities, one year or less, fair value	[3]	0
Held-to-maturity investment securities, debt maturities, after one year through five years, fair value	[3]	0
Held-to-maturity investment securities, debt maturities, after five years through ten years, fair value	[3]	0
Held-to-maturity investment securities, debt maturities, after ten years, fair value	[3]	273
Held-to-maturity investment securities, fair value	[2],[4]	$ 273	[3]	$ 233
[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.

Loan Receivables (Narrative) (D

Loan Receivables (Narrative) (Details) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)segment	Sep. 30, 2018USD ($)	Jun. 30, 2019USD ($)	Dec. 31, 2018USD ($)	Jun. 30, 2018USD ($)	Dec. 31, 2017USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loan portfolio segments (in segments) | segment				3
Private student loan forbearance lifetime cap (in months)				12 months
Private student loans including PCI in forbearance		$ 41		$ 41			$ 37
Private student loans in forbearance as a percentage of student loans in repayment and forbearance (in percent)		0.80%		0.80%			0.70%
Private student loans including PCI in repayment		$ 5,200		$ 5,200
Percentage of defaulted loans that were charged off at the end of the month in which they defaulted (in percent)		37.00%	34.00%	38.00%	35.00%
Provision for loan losses		$ 799	$ 742	$ 2,395	$ 2,235
Allowance for loan losses		$ 3,299	$ 2,927	$ 3,299	$ 2,927	$ 3,202	$ 3,041	$ 2,828	$ 2,621
Net charge-off rate (in percent)	[1]	3.05%	2.97%	3.17%	3.06%
Personal Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum period of payment reduction for the temporary reduced payment program (in months)				12 months
Maximum repayment term for temporary modification programs (in years)				9 years
Maximum repayment term for permanent modification programs (in years)				9 years
Credit Card Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum period of payment reduction for the temporary reduced payment program (in months)				12 months
Permanent workout program maturity (in months)				60 months
Interest and fees forgiven due to credit card loan modification program		$ 19	$ 12	$ 53	$ 35
Provision for loan losses		719	633	2,121	1,915
Allowance for loan losses		$ 2,799	$ 2,424	$ 2,799	$ 2,424	$ 2,691	2,528	$ 2,334	$ 2,147
Net charge-off rate (in percent)	[1]	3.32%	3.14%	3.43%	3.27%
PCI Student Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchased credit-impaired loans outstanding balance		$ 1,400		$ 1,400			1,700
Purchased credit-impaired loans	[2]	1,341		1,341			1,637
Provision for loan losses		0	$ 0	0	$ 0
Allowance for loan losses		$ 23		$ 23			$ 25
Threshold charge-off period for past due accounts (in days)		120 days		120 days
Net charge-off rate (in percent)		0.32%	0.64%	0.33%	0.71%
PCI Student Loans [Member] | 30 or More Days Delinquent [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Delinquency rate on PCI student loans (in percent)		2.90%		2.90%			2.93%
PCI Student Loans [Member] | 90 or More Days Delinquent [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Delinquency rate on PCI student loans (in percent)		0.72%		0.72%			0.78%
[1]	Net charge-off rate represents net charge-off dollars (annualized) divided by average loans for the reporting period.
[2]	Amounts include carrying values of $310 million and $363 million in loans pledged as collateral against the note issued from The Student Loan Corporation ("SLC") securitization trust at September 30, 2019 and December 31, 2018 , respectively. See Note 4: Credit Card and Student Loan Securitization Activities for additional information.

Loan Receivables (Schedule of L

Loan Receivables (Schedule of Loan Receivables) (Details) - USD ($) $ in Millions		Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables		$ 92,493		$ 90,512
Allowance for loan losses		(3,299)	$ (3,202)	(3,041)	$ (2,927)	$ (2,828)	$ (2,621)
Net loan receivables		89,194		87,471
Variable Interest Entity, Primary Beneficiary [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables		31,145		33,424
Allowance for loan losses		(1,167)		(1,150)
Credit Card Securitization Trusts [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit card loans	[1]	30,835		33,061
Allowance for loan losses	[1]	(1,167)		(1,150)
Net loan receivables		29,668		31,911
Seller's interest		13,578		11,050
Student Loan Securitization Trusts [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchased credit-impaired loans		310		363
Credit Card Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Credit card loans	[2]	73,968		72,876
Allowance for loan losses		(2,799)	(2,691)	(2,528)	(2,424)	(2,334)	(2,147)
Credit Card Loans [Member] | Credit Card Securitization Trusts [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Investors' interest		17,300		22,000
Seller's interest		13,600		11,100
Total Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables		17,184		15,999
Total Other Loans [Member] | Personal Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables		7,596		7,454
Allowance for loan losses		(348)	(338)	(338)	(323)	(313)	(301)
Total Other Loans [Member] | Private Student Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables		8,395		7,728
Total Other Loans [Member] | Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables		1,193		817
Allowance for loan losses		(5)	$ (6)	(6)	$ (11)	$ (11)	$ (11)
Purchase Credit-Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Purchased credit-impaired loans	[3]	1,341		1,637
Allowance for loan losses		(23)		(25)
Purchase Credit-Impaired 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		$ 310		$ 363
[1]	The Company maintains its allowance for loan losses at an amount sufficient to absorb probable losses inherent in 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]	Amounts include carrying values of $17.3 billion and $22.0 billion underlying investors' interest in trust debt at September 30, 2019 and December 31, 2018 , respectively, and $13.6 billion and $11.1 billion in seller's interest at September 30, 2019 and December 31, 2018 , respectively. See Note 4: Credit Card and Student Loan Securitization Activities for additional information.
[3]	Amounts include carrying values of $310 million and $363 million in loans pledged as collateral against the note issued from The Student Loan Corporation ("SLC") securitization trust at September 30, 2019 and December 31, 2018 , respectively. See Note 4: Credit Card and Student Loan Securitization Activities for additional information.

Loan Receivables (Schedule of D

Loan Receivables (Schedule of Delinquent and Non-Accruing Loans) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		$ 2,114		$ 2,114		$ 2,049
Loan receivables, 90 or more days delinquent and accruing		876		876		851
Loan receivables, total non-accruing		304		304		302
30-89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		1,146		1,146		1,088
90 or More Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		968		968		961
Credit Card Loans [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		1,847		1,847		1,772
Loan receivables, 90 or more days delinquent and accruing	[1]	809		809		781
Loan receivables, total non-accruing	[2]	269		269		266
Estimated gross interest income that would have been recorded based on original terms		12	$ 9	34	$ 28
Credit Card Loans [Member] | Entity Loan Modification Program [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, 90 or more days delinquent and accruing		148		148		116
Credit Card Loans [Member] | 30-89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		950		950		885
Credit Card Loans [Member] | 90 or More Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		897		897		887
Total Other Loans [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		267		267		277
Loan receivables, 90 or more days delinquent and accruing		67		67		70
Loan receivables, total non-accruing		35		35		36
Total Other Loans [Member] | 30-89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		196		196		203
Total Other Loans [Member] | 90 or More Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		71		71		74
Total Other Loans [Member] | Personal Loans [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		113		113		119
Loan receivables, 90 or more days delinquent and accruing	[3]	32		32		33
Loan receivables, total non-accruing		12		12		11
Total Other Loans [Member] | Personal Loans [Member] | Entity Loan Modification Program [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, 90 or more days delinquent and accruing		8		8		5
Total Other Loans [Member] | Personal Loans [Member] | 30-89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		79		79		84
Total Other Loans [Member] | Personal Loans [Member] | 90 or More Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		34		34		35
Total Other Loans [Member] | Private Student Loans (Excluding PCI) [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		150		150		155
Loan receivables, 90 or more days delinquent and accruing	[4]	35		35		37
Loan receivables, total non-accruing		9		9		8
Total Other Loans [Member] | Private Student Loans (Excluding PCI) [Member] | Entity Loan Modification Program [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, 90 or more days delinquent and accruing		9		9		7
Total Other Loans [Member] | Private Student Loans (Excluding PCI) [Member] | 30-89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		114		114		117
Total Other Loans [Member] | Private Student Loans (Excluding PCI) [Member] | 90 or More Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		36		36		38
Total Other Loans [Member] | Other Loans [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		4		4		3
Loan receivables, 90 or more days delinquent and accruing		0		0		0
Loan receivables, total non-accruing		14		14		17
Total Other Loans [Member] | Other Loans [Member] | 30-89 Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		3		3		2
Total Other Loans [Member] | Other Loans [Member] | 90 or More Days Delinquent [Member]
Financing Receivable, Past Due [Line Items]
Loan receivables, past due		$ 1		$ 1		$ 1
[1]	Credit card loans that are 90 or more days delinquent and accruing interest include $148 million and $116 million of loans accounted for as TDRs at September 30, 2019 and December 31, 2018 , respectively.
[2]	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 $12 million and $9 million for the three months ended September 30, 2019 and 2018 , respectively, and $34 million and $28 million for the nine months ended September 30, 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.
[3]	Personal loans that are 90 or more days delinquent and accruing interest include $8 million and $5 million of loans accounted for as TDRs at September 30, 2019 and December 31, 2018 , respectively.
[4]	Private student loans that are 90 or more days delinquent and accruing interest include $9 million and $7 million of loans accounted for as TDRs at September 30, 2019 and December 31, 2018 , respectively.

Loan Receivables (Schedule of N

Loan Receivables (Schedule of Net Charge-offs) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Charge Offs [Line Items]
Net charge-offs		$ 702	$ 642	$ 2,135	$ 1,926
Net charge-off rate (in percent)	[1]	3.05%	2.97%	3.17%	3.06%
Excluding PCI Loans [Member]
Charge Offs [Line Items]
Net charge-offs		$ 702	$ 642	$ 2,135	$ 1,926
Net charge-off rate (in percent)	[1]	3.09%	3.03%	3.22%	3.13%
Credit Card Loans [Member]
Charge Offs [Line Items]
Net charge-offs		$ 611	$ 543	$ 1,850	$ 1,638
Net charge-off rate (in percent)	[1]	3.32%	3.14%	3.43%	3.27%
Total Other Loans [Member]
Charge Offs [Line Items]
Net charge-offs		$ 91	$ 99	$ 285	$ 288
Net charge-off rate (in percent)	[1]	2.13%	2.54%	2.30%	2.52%
Total Other Loans [Member] | Personal Loans [Member]
Charge Offs [Line Items]
Net charge-offs		$ 76	$ 77	$ 240	$ 222
Net charge-off rate (in percent)	[1]	3.99%	4.09%	4.28%	4.03%
Total Other Loans [Member] | Private Student Loans (Excluding PCI) [Member]
Charge Offs [Line Items]
Net charge-offs		$ 14	$ 22	$ 44	$ 65
Net charge-off rate (in percent)	[1]	0.69%	1.19%	0.73%	1.17%
Total Other Loans [Member] | Other Loans [Member]
Charge Offs [Line Items]
Net charge-offs		$ 1	$ 0	$ 1	$ 1
Net charge-off rate (in percent)	[1]	0.00%	0.00%	0.00%	0.13%
[1]	Net charge-off rate represents net charge-off dollars (annualized) divided by average loans for the reporting period.

Loan Receivables (Schedule of C

Loan Receivables (Schedule of Credit Risk Profile by FICO Score) (Details)		Sep. 30, 2019	Dec. 31, 2018
Credit Card Loans [Member] | FICO Score, 660 and Above [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
FICO scores as a percentage of class of loan receivables		81.00%	81.00%
Credit Card Loans [Member] | FICO Score, Less Than 660 Or No Score [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
FICO scores as a percentage of class of loan receivables		19.00%	19.00%
Total Other Loans [Member] | Personal Loans [Member] | FICO Score, 660 and Above [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
FICO scores as a percentage of class of loan receivables		94.00%	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]
FICO scores as a percentage of class of loan receivables		6.00%	6.00%
Total Other Loans [Member] | Private Student Loans (Excluding PCI) [Member] | FICO Score, 660 and Above [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
FICO scores as a percentage of class of loan receivables	[1]	95.00%	94.00%
Total Other Loans [Member] | Private Student Loans (Excluding PCI) [Member] | FICO Score, Less Than 660 Or No Score [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
FICO scores as a percentage of class of loan receivables	[1]	5.00%	6.00%
[1]	PCI loans are discussed under the heading "— Purchased Credit-Impaired Loans."

Loan Receivables (Schedule of_2

Loan Receivables (Schedule of Changes in the Allowance for Loan Losses) (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2019		Sep. 30, 2018	Sep. 30, 2019		Sep. 30, 2018
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, balance at beginning of period		$ 3,202		$ 2,828	$ 3,041		$ 2,621
Provision for loan losses		799		742	2,395		2,235
Charge-offs		(891)		(785)	(2,676)		(2,343)
Recoveries		189		143	541		417
Net charge-offs		(702)		(642)	(2,135)		(1,926)
Other	[1]			(1)	(2)		(3)
Allowance for loan losses, balance at end of period		3,299		2,927	3,299		2,927
Student Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, balance at beginning of period	[2]	167		170	169	[3]	162
Provision for loan losses	[2]	(6)		22	24		75
Charge-offs	[2]	(17)		(25)	(54)		(74)
Recoveries	[2]	3		3	10		9
Net charge-offs	[2]	(14)		(22)	(44)		(65)
Other	[1]			(1)	(2)		(3)
Allowance for loan losses, balance at end of period	[2]	147	[3]	169	147	[3]	169
Credit Card Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, balance at beginning of period		2,691		2,334	2,528		2,147
Provision for loan losses		719		633	2,121		1,915
Charge-offs		(784)		(674)	(2,347)		(2,021)
Recoveries		173		131	497		383
Net charge-offs		(611)		(543)	(1,850)		(1,638)
Other				0	0		0
Allowance for loan losses, balance at end of period		2,799		2,424	2,799		2,424
Total Other Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Net charge-offs		(91)		(99)	(285)		(288)
Total Other Loans [Member] | Personal Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, balance at beginning of period		338		313	338		301
Provision for loan losses		86		87	250		244
Charge-offs		(89)		(86)	(274)		(247)
Recoveries		13		9	34		25
Net charge-offs		(76)		(77)	(240)		(222)
Other				0	0		0
Allowance for loan losses, balance at end of period		348		323	348		323
Total Other Loans [Member] | Other Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, balance at beginning of period		6		11	6		11
Provision for loan losses		0		0	0		1
Charge-offs		(1)		0	(1)		(1)
Recoveries		0		0	0		0
Net charge-offs		(1)		0	(1)		(1)
Other				0	0		0
Allowance for loan losses, balance at end of period		$ 5		$ 11	$ 5		$ 11
[1]	Net change in reserves on PCI pools having no remaining non-accretable difference.
[2]	Includes both PCI and non-PCI private student loans.
[3]	Includes both PCI and non-PCI private student loans.

Loan Receivables (Schedule of_3

Loan Receivables (Schedule of Net Charge-offs of Interest and Fee Revenues on Loan Receivables) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Loans and Leases Receivable Disclosure [Abstract]
Interest and fees accrued subsequently charged off, net of recoveries (recorded as a reduction of interest income)	$ 127	$ 109	$ 382	$ 328
Fees accrued subsequently charged off, net of recoveries (recorded as a reduction to other income)	$ 29	$ 26	$ 90	$ 81

Loan Receivables (Schedule of A

Loan Receivables (Schedule of Allowance for Loan Losses and Recorded Investment in its Loan Portfolio by Impairment Methodology) (Details) - USD ($) $ in Millions		Sep. 30, 2019		Jun. 30, 2019	Dec. 31, 2018		Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses, collectively evaluated for impairment in accordance with ASC 450-20		$ 2,683			$ 2,646
Allowance for loan losses, evaluated for impairment in accordance with ASC 310-10-35	[1],[2]	593			370
Total allowance for loan losses		3,299		$ 3,202	3,041		$ 2,927	$ 2,828	$ 2,621
Recorded investment in loans, collectively evaluated for impairment in accordance with ASC 450-20		87,548			86,237
Recorded investment in loans, evaluated for impairment in accordance with ASC 310-10-35	[1],[2]	3,604			2,638
Loan receivables		92,493			90,512
Financial Asset Acquired with Credit Deterioration [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loans losses, acquired with deteriorated credit quality, evaluated in accordance with ASC 310-30		23			25
Recorded investment in loans, acquired with deteriorated credit quality, evaluated in accordance with ASC 310-30		1,341			1,637
Student Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total allowance for loan losses	[3]	147	[4]	167	169	[4]	169	170	162
Total recorded investment	[4]	9,736			9,365
Credit Card Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses, collectively evaluated for impairment in accordance with ASC 450-20		2,297			2,229
Allowance for loan losses, evaluated for impairment in accordance with ASC 310-10-35	[1],[2]	502			299
Total allowance for loan losses		2,799		2,691	2,528		2,424	2,334	2,147
Recorded investment in loans, collectively evaluated for impairment in accordance with ASC 450-20		70,860			70,628
Recorded investment in loans, evaluated for impairment in accordance with ASC 310-10-35	[1],[2]	3,108			2,248
Total recorded investment		73,968			72,876
Unpaid principal balance of modified loans accounted for as troubled debt restructurings		2,800			2,000
Credit Card Loans [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loans losses, acquired with deteriorated credit quality, evaluated in accordance with ASC 310-30		0			0
Recorded investment in loans, acquired with deteriorated credit quality, evaluated in accordance with ASC 310-30		0			0
Total Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan receivables		17,184			15,999
Total Other Loans [Member] | Personal Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses, collectively evaluated for impairment in accordance with ASC 450-20		287			292
Allowance for loan losses, evaluated for impairment in accordance with ASC 310-10-35	[1],[2]	61			46
Total allowance for loan losses		348		338	338		323	313	301
Recorded investment in loans, collectively evaluated for impairment in accordance with ASC 450-20		7,401			7,302
Recorded investment in loans, evaluated for impairment in accordance with ASC 310-10-35	[1],[2]	195			152
Total recorded investment		7,596			7,454
Loan receivables		7,596			7,454
Total Other Loans [Member] | Personal Loans [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loans losses, acquired with deteriorated credit quality, evaluated in accordance with ASC 310-30		0			0
Recorded investment in loans, acquired with deteriorated credit quality, evaluated in accordance with ASC 310-30		0			0
Total Other Loans [Member] | Private Student Loans (Excluding PCI) [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses, collectively evaluated for impairment in accordance with ASC 450-20		95			121
Allowance for loan losses, evaluated for impairment in accordance with ASC 310-10-35	[1],[2]	29			23
Recorded investment in loans, collectively evaluated for impairment in accordance with ASC 450-20		8,146			7,546
Recorded investment in loans, evaluated for impairment in accordance with ASC 310-10-35	[1],[2]	249			182
Loan receivables		8,395			7,728
Total Other Loans [Member] | Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses, collectively evaluated for impairment in accordance with ASC 450-20		4			4
Allowance for loan losses, evaluated for impairment in accordance with ASC 310-10-35	[1],[2]	1			2
Total allowance for loan losses		5		$ 6	6		$ 11	$ 11	$ 11
Recorded investment in loans, collectively evaluated for impairment in accordance with ASC 450-20		1,141			761
Recorded investment in loans, evaluated for impairment in accordance with ASC 310-10-35	[1],[2]	52			56
Total recorded investment		1,193			817
Loan receivables		1,193			817
Total Other Loans [Member] | Other Loans [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loans losses, acquired with deteriorated credit quality, evaluated in accordance with ASC 310-30		0			0
Recorded investment in loans, acquired with deteriorated credit quality, evaluated in accordance with ASC 310-30		0			0
PCI Student Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total allowance for loan losses		23			25
Recorded investment in loans, acquired with deteriorated credit quality, evaluated in accordance with ASC 310-30	[5]	1,341			1,637
PCI Student Loans [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loans losses, acquired with deteriorated credit quality, evaluated in accordance with ASC 310-30		23			25
Recorded investment in loans, acquired with deteriorated credit quality, evaluated in accordance with ASC 310-30		$ 1,341			$ 1,637
[1]	Loan receivables evaluated for impairment in accordance with Accounting Standards Codification ("ASC") 310-10-35 include credit card loans, personal loans and student loans collectively evaluated for impairment in accordance with ASC Subtopic 310-40, Receivables, which consists of modified loans accounted for as TDRs. Other loans are individually evaluated for impairment and generally do not represent TDRs.
[2]	The unpaid principal balance of credit card loans was $2.8 billion and $2.0 billion at September 30, 2019 and December 31, 2018 , respectively. All loans accounted for as TDRs have a related allowance for loan losses.
[3]	Includes both PCI and non-PCI private student loans.
[4]	Includes both PCI and non-PCI private student loans.
[5]	Amounts include carrying values of $310 million and $363 million in loans pledged as collateral against the note issued from The Student Loan Corporation ("SLC") securitization trust at September 30, 2019 and December 31, 2018 , respectively. See Note 4: Credit Card and Student Loan Securitization Activities for additional information.

Loan Receivables (Schedule of T

Loan Receivables (Schedule of Troubled Debt Restructurings) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Credit Card Loans [Member]
Financing Receivable, Modifications [Line Items]
Average recorded investment in loans	[1]	$ 2,960	$ 1,815	$ 2,682	$ 1,612
Interest income recognized during period loans were impaired	[1],[2]	93	48	245	123
Gross interest income that would have been recorded with original terms	[1],[3]	53	37	148	95
Credit Card Loans [Member] | Loans no longer in a modification program
Financing Receivable, Modifications [Line Items]
Average recorded investment in loans		985	427	833	404
Total Other Loans [Member] | Personal Loans [Member]
Financing Receivable, Modifications [Line Items]
Average recorded investment in loans		188	134	174	125
Interest income recognized during period loans were impaired	[2]	5	4	13	10
Gross interest income that would have been recorded with original terms	[3]	3	1	7	4
Total Other Loans [Member] | Private Student Loans [Member]
Financing Receivable, Modifications [Line Items]
Average recorded investment in loans		239	166	215	152
Interest income recognized during period loans were impaired	[2]	5	3	13	9
Gross interest income that would have been recorded with original terms	[3]	$ 1	$ 0	$ 1	$ 0
[1]	Includes credit card loans that were modified in TDRs, but are no longer enrolled in a TDR program due to noncompliance with the terms of the modification or due to successful completion of a program after which charging privileges may be reinstated based on customer-level evaluation. The average balance of credit card loans that were no longer enrolled in a TDR program was $985 million and $427 million for the three months ended September 30, 2019 and 2018 , respectively, and $833 million and $404 million for the nine months ended September 30, 2019 and 2018 , respectively.
[2]	The Company does not separately track interest income on loans in modification programs. Amounts shown are estimated by applying an average interest rate to the average loans in the various modification programs.
[3]	The Company does not separately track the amount of additional gross interest income that would have been recorded if the loans in modification programs had not been restructured and interest had instead been recorded in accordance with the original terms. Amounts shown are estimated by applying the difference between the average interest rate earned on non-impaired loans and the average interest rate earned on loans in the modification programs to the average loans in the modification programs.

Loan Receivables (Schedule of_4

Loan Receivables (Schedule of Loans That Entered a Modification Program During the Period) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019USD ($)accounts	Sep. 30, 2018USD ($)accounts	Sep. 30, 2019USD ($)accounts	Sep. 30, 2018USD ($)accounts
Credit Card Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts that entered a loan modification program during the period, number of accounts (in accounts) | accounts	97,046	69,127	273,970	185,185
Accounts that entered a loan modification program during the period, balances | $	$ 623	$ 444	$ 1,766	$ 1,187
Total Other Loans [Member] | Personal Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts that entered a loan modification program during the period, number of accounts (in accounts) | accounts	2,859	1,903	8,129	5,867
Accounts that entered a loan modification program during the period, balances | $	$ 39	$ 27	$ 110	$ 79
Total Other Loans [Member] | Private Student Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts that entered a loan modification program during the period, number of accounts (in accounts) | accounts	1,692	935	4,978	2,887
Accounts that entered a loan modification program during the period, balances | $	$ 31	$ 17	$ 92	$ 54

Loan Receivables (Schedule of_5

Loan Receivables (Schedule of Troubled Debt Restructurings That Subsequently Defaulted) (Details) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019USD ($)accounts	Sep. 30, 2018USD ($)accounts	Sep. 30, 2019USD ($)accountsmissed_payments	Sep. 30, 2018USD ($)accounts
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amount of missed payments after which a customer defaults from a modification program (in payments) | missed_payments				2
Credit Card Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings that subsequently defaulted, number of accounts (in accounts) | accounts	[1],[2]	19,108	10,535	50,980	28,319
Troubled debt restructurings that subsequently defaulted, aggregated outstanding balances upon default | $	[1],[2]	$ 109	$ 60	$ 294	$ 156
Total Other Loans [Member] | Personal Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings that subsequently defaulted, number of accounts (in accounts) | accounts	[2]	1,131	847	2,925	2,059
Troubled debt restructurings that subsequently defaulted, aggregated outstanding balances upon default | $	[2]	$ 15	$ 11	$ 42	$ 27
Total Other Loans [Member] | Private Student Loans [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Troubled debt restructurings that subsequently defaulted, number of accounts (in accounts) | accounts	[3]	396	278	966	753
Troubled debt restructurings that subsequently defaulted, aggregated outstanding balances upon default | $	[3]	$ 8	$ 5	$ 19	$ 13
Delinquency days to default (in days)				60 days
[1]	Terms revert back to the pre-modification terms for customers who default from a temporary program and charging privileges remain revoked in most cases.
[2]	For credit card loans and personal loans, a customer defaults from a modification program after two
[3]	For student loans, defaults have been defined as loans that are 60

Loan Receivables (Schedule of_6

Loan Receivables (Schedule of Changes in Accretable Yield for the Acquired Loans) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Accretable yield, balance at beginning of period	$ 508	$ 608	$ 548	$ 669
Accretion into interest income	(29)	(34)	(92)	(106)
Other changes in expected cash flows	0	1	23	12
Accretable yield, balance at end of period	$ 479	$ 575	$ 479	$ 575

Credit Card and Student Loan _3

Credit Card and Student Loan Securitization Activities (Narrative) (Details)	9 Months Ended
	Sep. 30, 2019classestrust
Student Loan Securitization Trusts [Member]
Variable Interest Entity [Line Items]
Number of trusts issuing securities | trust	1
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) | 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		Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Restricted cash		$ 37		$ 1,846	$ 590
Allowance for loan losses allocated to securitized loan receivables		(3,299)	$ (3,202)	(3,041)	$ (2,927)	$ (2,828)	$ (2,621)
Net loan receivables		89,194		87,471
Other		2,389		2,215
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Restricted cash		37		1,846
Allowance for loan losses allocated to securitized loan receivables		(1,167)		(1,150)
Other		6		7
Variable Interest Entity, Primary Beneficiary [Member] | Credit Card Securitization Trusts [Member]
Variable Interest Entity [Line Items]
Restricted cash		26		1,834
Investors' interests held by third-party investors		12,600		16,800
Investors' interests held by wholly-owned subsidiaries of Discover Bank		4,657		5,211
Seller's interest		13,578		11,050
Loan receivables	[1]	30,835		33,061
Allowance for loan losses allocated to securitized loan receivables	[1]	(1,167)		(1,150)
Net loan receivables		29,668		31,911
Other		6		7
Carrying value of assets of consolidated variable interest entities		$ 29,700		$ 33,752
[1]	The Company maintains its allowance for loan losses at an amount sufficient to absorb probable losses inherent in 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.

Credit Card and Student Loan _5

Credit Card and Student Loan Securitization Activities (Schedule of Restricted Student Loan Securitized Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Variable Interest Entity [Line Items]
Restricted cash	$ 37	$ 1,846	$ 590
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Restricted cash	37	1,846
Variable Interest Entity, Primary Beneficiary [Member] | Student Loan Securitization Trusts [Member]
Variable Interest Entity [Line Items]
Restricted cash	11	12
Purchased credit-impaired loans	310	363
Carrying value of assets of consolidated variable interest entities	$ 321	$ 375

Deposits (Narrative) (Details)

Deposits (Narrative) (Details)	9 Months Ended
	Sep. 30, 2019channels
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		Sep. 30, 2019	Dec. 31, 2018
Deposits [Abstract]
Certificates of deposit in amounts less than $100,000		$ 25,248	$ 27,947
Certificates of deposit in amounts $100,000 or greater	[1]	8,736	6,841
Savings deposits, including money market deposit accounts		36,343	32,296
Total interest-bearing deposits		70,327	67,084
Certificates of deposit equal to or greater than $250,000		$ 2,400	$ 1,700
[1]	Includes $2.4 billion and $1.7 billion in certificates of deposit equal to or greater than $250,000, the Federal Deposit Insurance Corporation ("FDIC") insurance limit, as of September 30, 2019 and December 31, 2018 , respectively.

Deposits (Schedule of $100,000

Deposits (Schedule of $100,000 or More Certificates of Deposit Maturities) (Details) - USD ($) $ in Millions		Sep. 30, 2019	Dec. 31, 2018
Deposits [Abstract]
Three months or less		$ 1,370
Over three months through six months		1,502
Over six months through twelve months		3,311
Over twelve months		2,553
Total	[1]	$ 8,736	$ 6,841
[1]	Includes $2.4 billion and $1.7 billion in certificates of deposit equal to or greater than $250,000, the Federal Deposit Insurance Corporation ("FDIC") insurance limit, as of September 30, 2019 and December 31, 2018 , respectively.

Deposits (Schedule of Certifica

Deposits (Schedule of Certificates of Deposit Maturities) (Details) $ in Millions	Sep. 30, 2019USD ($)
Deposits [Abstract]
2019	$ 4,122
2020	15,328
2021	6,382
2022	3,178
2023	1,896
Thereafter	3,078
Total	$ 33,984

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 Millions	Sep. 30, 2019USD ($)
Debt Instrument [Line Items]
Total commitment of secured credit facilities	$ 6,000
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		9 Months Ended
		Sep. 30, 2019		Dec. 31, 2018
Debt Instrument [Line Items]
Long-term borrowings (in dollars)		$ 24,454		$ 27,228
Variable Interest Entity, Primary Beneficiary [Member]
Debt Instrument [Line Items]
Long-term borrowings (in dollars)		12,820		16,917
Securitized Debt [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Debt Instrument [Line Items]
Long-term borrowings (in dollars)		12,820		16,917
Securitized Debt [Member] | Discover Card Master Trust I and Discover Card Execution Note Trust [Member]
Debt Instrument [Line Items]
Long-term borrowings (in dollars)		$ 12,651		16,720
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		2.58%
Long-term borrowings (in dollars)	[1]	$ 7,637		10,657
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		1.39%
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		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		2.41%
Long-term borrowings (in dollars)	[3]	$ 5,014	[2]	6,063
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		2.26%
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		2.63%
Securitized Debt [Member] | Discover Card Master Trust I and Discover Card Execution Note Trust [Member] | Floating Rate Asset Backed Securities 1-Month LIBOR Plus 23 to 60 Basis Points [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 1-Month LIBOR Plus 23 to 60 Basis Points [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 1-Month LIBOR Plus 23 to 60 Basis Points [Member] | Maximum [Member]
Debt Instrument [Line Items]
Basis spread on variable rate		0.60%
Securitized Debt [Member] | SLC Private Student Loan Trust [Member]
Debt Instrument [Line Items]
Long-term borrowings (in dollars)		$ 169		197
Securitized Debt [Member] | SLC Private Student Loan Trust [Member] | Floating-Rate Asset-Backed Securities [Member]
Debt Instrument [Line Items]
Interest rate		6.00%
Weighted-average interest rate		6.00%
Long-term borrowings (in dollars)	[4]	$ 169	[5]	197
Securitized Debt [Member] | SLC Private Student Loan Trust [Member] | Floating Rate Asset Backed Securities Prime Rate Plus 100 Basis Points [Member]
Debt Instrument [Line Items]
Interest rate terms		Prime rate + 100 basis points
Basis spread on variable rate		1.00%
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 (in dollars)		$ 3,287		2,743
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 (in dollars)		$ 339		346
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		3.55%
Long-term borrowings (in dollars)	[1]	$ 6,811		6,027
Senior Notes [Member] | Discover Bank [Member] | Fixed-Rate Senior Bank Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate		2.45%
Senior Notes [Member] | Discover Bank [Member] | Fixed-Rate Senior Bank Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate		4.65%
Subordinated Debt [Member] | Discover Bank [Member] | Fixed-Rate Subordinated Bank Notes [Member]
Debt Instrument [Line Items]
Weighted-average interest rate		6.32%
Long-term borrowings (in dollars)		$ 1,197		$ 1,195
Subordinated Debt [Member] | Discover Bank [Member] | Fixed-Rate Subordinated Bank Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest rate		4.68%
Subordinated Debt [Member] | Discover Bank [Member] | Fixed-Rate Subordinated Bank Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest rate		8.70%
[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 14: 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 September 30, 2019 .
[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 14: 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]	SLC Private Student Loan Trust floating-rate asset-backed security includes an issuance with the following interest rate term: Prime rate + 100 basis points as of September 30, 2019 .

Long-Term Borrowings (Schedul_2

Long-Term Borrowings (Schedule of Long-Term Borrowings Maturities) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
2019	$ 200
2020	4,745
2021	4,218
2022	4,124
2023	3,329
Thereafter	7,838
Total	$ 24,454	$ 27,228

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Schedule of Changes in Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax, balance at beginning of period				$ (156)
Cumulative effect of ASU No. 2018-02 adoption					$ 0
Net change in accumulated other comprehensive income (loss), net of tax		$ 9	$ 2	82	21
Accumulated other comprehensive income (loss), net of tax, balance at end of period		(74)		(74)
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	(14)	10	(5)
Cumulative effect of ASU No. 2018-02 adoption	[1]				(1)
Net change in accumulated other comprehensive income (loss), net of tax		17	(2)	119	(10)
Accumulated other comprehensive income (loss), net of tax, balance at end of period		129	(16)	129	(16)
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		(8)	39	22	10
Cumulative effect of ASU No. 2018-02 adoption	[1]				3
Net change in accumulated other comprehensive income (loss), net of tax		(8)	4	(38)	30
Accumulated other comprehensive income (loss), net of tax, balance at end of period		(16)	43	(16)	43
Gains (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		(187)	(187)	(188)	(157)
Cumulative effect of ASU No. 2018-02 adoption	[1]				(31)
Net change in accumulated other comprehensive income (loss), net of tax		0	0	1	1
Accumulated other comprehensive income (loss), net of tax, balance at end of period		(187)	(187)	(187)	(187)
AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss), net of tax, balance at beginning of period		(83)	(162)	(156)	(152)
Cumulative effect of ASU No. 2018-02 adoption	[1]				(29)
Net change in accumulated other comprehensive income (loss), net of tax		9	2	82	21
Accumulated other comprehensive income (loss), net of tax, balance at end of period		$ (74)	$ (160)	$ (74)	$ (160)
[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	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 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	$ 24	$ (4)	$ 158	$ (14)
Available-for-sale investment securities, net unrealized holding gains (losses) arising during the period, tax benefit (expense)	(7)	2	(39)	4
Available-for-sale investment securities, net unrealized holding gains (losses) arising during the period, net of tax	17	(2)	119	(10)
Available-for-sale investment securities, net change, before tax	24	(4)	158	(14)
Available-for-sale investment securities, net change, tax benefit (expense)	(7)	2	(39)	4
Available-for-sale investment securities, net change, net of tax	17	(2)	119	(10)
Cash flow hedges, net unrealized gains (losses) arising during the period, before tax	(9)	8	(44)	42
Cash flow hedges, net unrealized gains (losses) arising during the period, tax benefit (expense)	2	(2)	11	(10)
Cash flow hedges, net unrealized gains (losses) arising during the period, net of tax	(7)	6	(33)	32
Cash flow hedges, amounts reclassified from AOCI, before tax	(2)	(2)	(7)	(2)
Cash flow hedges, amounts reclassified from AOCI, tax benefit (expense)	1	0	2	0
Cash flow hedges, amounts reclassified from AOCI, net of tax	(1)	(2)	(5)	(2)
Cash flow hedges, net change, before tax	(11)	6	(51)	40
Cash flow hedges, net change, tax benefit (expense)	3	(2)	13	(10)
Cash flow hedges, net change, net of tax	$ (8)	$ 4	(38)	30
Pension plan, unrealized gains (losses) arising during the period, before tax			1	1
Pension plan, unrealized gains (losses) arising during the period, tax benefit (expense)			0	0
Pension plan, unrealized gains (losses) arising during the period, net of tax			1	1
Pension plan, net change, before tax			1	1
Pension plan, net change, tax benefit (expense)			0	0
Pension plan, net change, net of tax			$ 1	$ 1

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details)	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Change in Effective Income Tax Rate	(3.00%)	(1.20%)

Income Taxes (Schedule of Effec

Income Taxes (Schedule of Effective Income Tax Rate Calculation) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income before income tax expense	$ 994	$ 967	$ 2,911	$ 2,700
Income tax expense	$ 224	$ 247	$ 662	$ 645
Effective income tax rate (in percent)	22.50%	25.50%	22.70%	23.90%

Earnings Per Share (Schedule of

Earnings Per Share (Schedule of Basic and Diluted EPS ) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net income	$ 770	$ 720	$ 2,249	$ 2,055
Preferred stock dividends	(15)	(15)	(31)	(31)
Net income available to common stockholders	755	705	2,218	2,024
Income allocated to participating securities	(6)	(6)	(15)	(16)
Net income allocated to common stockholders	749	699	2,203	2,008
Income allocated to participating securities, diluted	(6)	(6)	(15)	(16)
Net income allocated to common stockholders, diluted	$ 749	$ 699	$ 2,203	$ 2,008
Denominator:
Weighted-average shares of common stock outstanding	317	341	323	348
Effect of dilutive common stock equivalents	0	1	0	0
Weighted-average shares of common stock outstanding and common stock equivalents	317	342	323	348
Basic earnings per common share (in dollars per share)	$ 2.36	$ 2.05	$ 6.83	$ 5.77
Diluted earnings per common share (in dollars per share)	$ 2.36	$ 2.05	$ 6.82	$ 5.77

Capital Adequacy (Schedule of M

Capital Adequacy (Schedule of Minimum and Well-Capitalized Requirements) (Details) - USD ($) $ in Millions		Sep. 30, 2019	Dec. 31, 2018
Discover Bank [Member]
Compliance with Regulatory Capital Requirements [Line Items]
Total capital to risk-weighted assets, actual amount		$ 13,354	$ 13,106
Total capital to risk-weighted assets, actual ratio (in percent)	[1]	14.20%
Total capital to risk-weighted assets, minimum capital requirements, amount		$ 7,515	$ 7,372
Total capital to risk-weighted assets, minimum capital requirements, ratio (in percent)		8.00%	8.00%
Total capital to risk-weighted assets, capital requirements to be classified as well-capitalized, amount		$ 9,394	$ 9,215
Total capital to risk-weighted assets, capital requirements to be classified as well-capitalized, ratio (in percent)		10.00%	10.00%
Tier I capital to risk-weighted assets, actual amount		$ 11,157	$ 10,834
Tier I capital to risk-weighted assets, actual ratio (in percent)	[1]	11.90%
Tier I capital to risk-weighted assets, minimum capital requirements, amount		$ 5,637	$ 5,529
Tier I capital to risk-weighted assets, minimum capital requirements, ratio (in percent)		6.00%	6.00%
Tier I capital to risk-weighted assets, capital requirements to be classified as well-capitalized, amount		$ 7,515	$ 7,372
Tier I capital to risk-weighted assets, capital requirements to be classified as well-capitalized, ratio (in percent)		8.00%	8.00%
Tier I capital to average assets, actual amount		$ 11,157	$ 10,834
Tier I capital to average assets, actual ratio (in percent)	[1]	10.20%
Tier I capital to average assets, minimum capital requirements, amount		$ 4,362	$ 4,265
Tier I capital to average assets, minimum capital requirements, ratio (in percent)		4.00%	4.00%
Tier I capital to average assets, capital requirements to be classified as well-capitalized, amount		$ 5,452	$ 5,332
Tier I capital to average assets, capital requirements to be classified as well-capitalized, ratio (in percent)		5.00%	5.00%
CET1 capital to risk-weighted assets, actual amount		$ 11,157	$ 10,834
CET1 capital to risk-weighted assets, actual ratio (in percent)	[1]	11.90%
CET1 capital to risk-weighted assets, minimum capital requirements, amount		$ 4,227	$ 4,147
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		$ 6,106	$ 5,990
CET1 capital to risk-weighted assets, capital requirements to be classified as well-capitalized, ratio (in percent)		6.50%	6.50%
Parent Company [Member]
Compliance with Regulatory Capital Requirements [Line Items]
Total capital to risk-weighted assets, actual amount		$ 13,009	$ 12,532
Total capital to risk-weighted assets, minimum capital requirements, amount		$ 7,598	$ 7,450
Total capital to risk-weighted assets, minimum capital requirements, ratio (in percent)		8.00%	8.00%
Total capital to risk-weighted assets, capital requirements to be classified as well-capitalized, amount	[2]	$ 9,498	$ 9,312
Total capital to risk-weighted assets, capital requirements to be classified as well-capitalized, ratio (in percent)	[2]	10.00%	10.00%
Tier I capital to risk-weighted assets, actual amount		$ 11,403	$ 10,895
Tier I capital to risk-weighted assets, actual ratio (in percent)	[1]	12.00%
Tier I capital to risk-weighted assets, minimum capital requirements, amount		$ 5,699	$ 5,587
Tier I capital to risk-weighted assets, minimum capital requirements, ratio (in percent)		6.00%	6.00%
Tier I capital to risk-weighted assets, capital requirements to be classified as well-capitalized, amount	[2]	$ 5,699	$ 5,587
Tier I capital to risk-weighted assets, capital requirements to be classified as well-capitalized, ratio (in percent)	[2]	6.00%	6.00%
Tier I capital to average assets, actual amount		$ 11,403	$ 10,895
Tier I capital to average assets, actual ratio (in percent)	[1]	10.30%
Tier I capital to average assets, minimum capital requirements, amount		$ 4,409	$ 4,308
Tier I capital to average assets, minimum capital requirements, ratio (in percent)		4.00%	4.00%
CET1 capital to risk-weighted assets, actual amount		$ 10,840	$ 10,332
CET1 capital to risk-weighted assets, actual ratio (in percent)	[1]	11.40%
CET1 capital to risk-weighted assets, minimum capital requirements, amount		$ 4,274	$ 4,191
CET1 capital to risk-weighted assets, minimum capital requirements, ratio (in percent)		4.50%	4.50%
Transition [Member] | Discover Bank [Member]
Compliance with Regulatory Capital Requirements [Line Items]
Total capital to risk-weighted assets, actual ratio (in percent)	[1]		14.20%
Tier I capital to risk-weighted assets, actual ratio (in percent)	[1]		11.80%
Tier I capital to average assets, actual ratio (in percent)	[1]		10.20%
CET1 capital to risk-weighted assets, actual ratio (in percent)	[1]		11.80%
Transition [Member] | Parent Company [Member]
Compliance with Regulatory Capital Requirements [Line Items]
Total capital to risk-weighted assets, actual ratio (in percent)	[1]	13.70%	13.50%
Tier I capital to risk-weighted assets, actual ratio (in percent)	[1]		11.70%
Tier I capital to average assets, actual ratio (in percent)	[1]		10.10%
CET1 capital to risk-weighted assets, actual ratio (in percent)	[1]		11.10%
[1]	Capital ratios are calculated based on the Basel III Standardized Approach rules, subject to applicable 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	Sep. 30, 2019	Dec. 31, 2018
Commitments, Contingencies and Guarantees [Line Items]
Guarantor obligations, maximum exposure, undiscounted	$ 200
Escrow deposits and settlement withholdings	8	$ 10
Commitments to Extend Credit [Member]
Commitments, Contingencies and Guarantees [Line Items]
Unused commitments to extend credit for loans	$ 206,800

Commitments, Contingencies an_4

Commitments, Contingencies and Guarantees (Schedule of Merchant Chargeback Guarantee) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Merchant Chargeback Guarantees [Member]
Loss Contingencies [Line Items]
Aggregate sales transaction volume	[1]	$ 44,332	$ 40,806	$ 125,922	$ 116,800
[1]	Represents period 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 (Narrative) (Details) - USD ($) $ in Millions	Jul. 22, 2015	Sep. 30, 2019
Unfavorable Regulatory Action [Member] | Consumer Financial Protection Bureau Consent Order [Member]
Loss Contingencies [Line Items]
Amount of civil money penalty for consent order	$ 2.5
Maximum [Member] | Pending and Threatened Litigation [Member]
Loss Contingencies [Line Items]
Aggregate range of reasonably possible losses		$ 125
Minimum [Member] | Unfavorable Regulatory Action [Member] | Consumer Financial Protection Bureau Consent Order [Member]
Loss Contingencies [Line Items]
Aggregate range of reasonably possible losses	$ 16

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Residential Mortgage-Backed Securities - Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale securities, par value	$ 442		$ 442
Available for sale securities, weighted average coupon rate (in percent)	2.81%		2.81%
Available for sale securities, weighted average remaining maturity (in years)			2 years
Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset transfers from level 1 to level 2 within the fair value hierarchy	$ 0	$ 0	$ 0	$ 0
Asset transfers from level 2 to level 1 within the fair value hierarchy	0	0	0	0
Liability transfers from level 1 to level 2 within the fair value hierarchy	0	0	0	0
Liability transfers from level 2 to level 1 within the fair value hierarchy	0	0	0	0
Fair Value, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of assets measured at fair value on a non-recurring basis	$ 0	$ 0	$ 0	$ 0

Fair Value Measurements (Schedu

Fair Value Measurements (Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions		Sep. 30, 2019		Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities, fair value	[1]	$ 10,380		$ 3,133
U.S. Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities, fair value	[1]	9,930		2,586
Residential Mortgage-Backed Securities - Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities, fair value	[1]	450	[2]	547
Fair Value, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities, fair value		10,380		3,133
Fair Value, Recurring [Member] | U.S. Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities, fair value		9,930		2,586
Fair Value, Recurring [Member] | Residential Mortgage-Backed Securities - Agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities, fair value		450		547
Fair Value, Recurring [Member] | Interest Rate Swaps [Member] | Cash Flow Hedging [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets, fair value	[3]			8
Derivative financial instruments, liabilities, fair value	[3]	3		2
Fair Value, Recurring [Member] | Interest Rate Swaps [Member] | Fair Value Hedging [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets, fair value	[3]			5
Derivative financial instruments, liabilities, fair value	[3]	1
Fair Value, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities, fair value		9,930		2,586
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]
Available-for-sale investment securities, fair value		9,930		2,586
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]
Available-for-sale investment securities, fair value		0		0
Fair Value, Recurring [Member] | Level 1 [Member] | Interest Rate Swaps [Member] | Cash Flow Hedging [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets, fair value				0
Derivative financial instruments, liabilities, fair value		0		0
Fair Value, Recurring [Member] | Level 1 [Member] | Interest Rate Swaps [Member] | Fair Value Hedging [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets, fair value				0
Derivative financial instruments, liabilities, fair value		0
Fair Value, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities, fair value		450		547
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]
Available-for-sale investment securities, fair value		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]
Available-for-sale investment securities, fair value		450		547
Fair Value, Recurring [Member] | Level 2 [Member] | Interest Rate Swaps [Member] | Cash Flow Hedging [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets, fair value	[3]			8
Derivative financial instruments, liabilities, fair value	[3]	3		2
Fair Value, Recurring [Member] | Level 2 [Member] | Interest Rate Swaps [Member] | Fair Value Hedging [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets, fair value	[3]			5
Derivative financial instruments, liabilities, fair value	[3]	1
Fair Value, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investment securities, fair value		0		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]
Available-for-sale investment securities, fair value		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]
Available-for-sale investment securities, fair value		0		0
Fair Value, Recurring [Member] | Level 3 [Member] | Interest Rate Swaps [Member] | Cash Flow Hedging [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets, fair value				0
Derivative financial instruments, liabilities, fair value		0		0
Fair Value, Recurring [Member] | Level 3 [Member] | Interest Rate Swaps [Member] | Fair Value Hedging [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments, assets, fair value				$ 0
Derivative financial instruments, liabilities, fair value		$ 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 condensed 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		Sep. 30, 2019		Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities	[1]	$ 273		$ 233
Residential Mortgage-Backed Securities - Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities	[1],[2]	273	[3]	233
Fair Value, Nonrecurring [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities		273		233
Net loan receivables		92,855		90,787
Cash and cash equivalents	[4]	6,075		13,299
Restricted cash	[4]	37		1,846
Other short-term investments	[4]	1,000
Accrued interest receivables	[4],[5]	1,054		951
Time deposits	[6]	34,478		34,635
Long-term borrowings		25,262		27,243
Accrued interest payables	[4],[5]	243		292
Fair Value, Nonrecurring [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term borrowings		12,348		10,325
Fair Value, Nonrecurring [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term borrowings		12,914		16,918
Fair Value, Nonrecurring [Member] | Residential Mortgage-Backed Securities - Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities		273		233
Fair Value, Nonrecurring [Member] | Carrying Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities		269		237
Net loan receivables		89,194		87,471
Cash and cash equivalents	[4]	6,075		13,299
Restricted cash	[4]	37		1,846
Other short-term investments	[4]	1,000
Accrued interest receivables	[4],[5]	1,054		951
Time deposits	[6]	33,984		34,788
Long-term borrowings		24,454		27,228
Accrued interest payables	[4],[5]	243		292
Fair Value, Nonrecurring [Member] | Carrying Value [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term borrowings		11,634		10,311
Fair Value, Nonrecurring [Member] | Carrying Value [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term borrowings		12,820		16,917
Fair Value, Nonrecurring [Member] | Carrying Value [Member] | Residential Mortgage-Backed Securities - Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities		269		237
Fair Value, Nonrecurring [Member] | 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]	6,075		13,299
Restricted cash	[4]	37		1,846
Other short-term investments	[4]	1,000
Accrued interest receivables		0		0
Time deposits		0		0
Long-term borrowings		0		0
Accrued interest payables		0		0
Fair Value, Nonrecurring [Member] | 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
Fair Value, Nonrecurring [Member] | Level 1 [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term borrowings		0		0
Fair Value, Nonrecurring [Member] | 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
Fair Value, Nonrecurring [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities		273		233
Net loan receivables		0		0
Cash and cash equivalents		0		0
Restricted cash		0		0
Other short-term investments		0
Accrued interest receivables	[4],[5]	1,054		951
Time deposits	[6]	34,478		34,635
Long-term borrowings		25,077		27,026
Accrued interest payables	[4],[5]	243		292
Fair Value, Nonrecurring [Member] | Level 2 [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term borrowings		12,348		10,325
Fair Value, Nonrecurring [Member] | Level 2 [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term borrowings		12,729		16,701
Fair Value, Nonrecurring [Member] | Level 2 [Member] | Residential Mortgage-Backed Securities - Agency [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities		273		233
Fair Value, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity investment securities		0		0
Net loan receivables		92,855		90,787
Cash and cash equivalents		0		0
Restricted cash		0		0
Other short-term investments		0
Accrued interest receivables		0		0
Time deposits		0		0
Long-term borrowings		185		217
Accrued interest payables		0		0
Fair Value, Nonrecurring [Member] | 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
Fair Value, Nonrecurring [Member] | Level 3 [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term borrowings		185		217
Fair Value, Nonrecurring [Member] | 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
[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 the nature of their liquidity (i.e., due or payable in less than one year).
[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 condensed 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	9 Months Ended
	Sep. 30, 2019USD ($)
Derivative [Line Items]
Additional collateral	$ 20
Interest Expense [Member]
Derivative [Line Items]
Cash flow hedge gain (loss) to be reclassified within twelve months	$ 5
Deposits [Member]
Derivative [Line Items]
Initial maximum period for cash flow hedges (in years)	7 years
Securitized Debt [Member]
Derivative [Line Items]
Initial maximum period for cash flow hedges (in years)	7 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		Sep. 30, 2019USD ($)transactions		Sep. 30, 2019GBP (£)transactions	Sep. 30, 2019SGD ($)transactions	Sep. 30, 2019EUR (€)transactions	Sep. 30, 2019INR (₨)transactions	Dec. 31, 2018USD ($)transactions		Dec. 31, 2018GBP (£)transactions	Dec. 31, 2018SGD ($)transactions	Dec. 31, 2018EUR (€)transactions	Dec. 31, 2018INR (₨)transactions
Derivatives, Fair Value [Line Items]
Derivative assets	[1]	$ 0						$ 13
Collateral held, derivative assets	[2]	0						(8)
Total net derivative assets		0						5
Derivative liabilities	[1]	4						2
Collateral posted, derivative liabilities	[2]	(4)						(2)
Total net derivative liabilities		0						0
Designated as Hedges [Member] | Cash Flow Hedging [Member] | Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		$ 1,650						2,450
Derivative, number of outstanding derivative contracts (in transactions) | transactions		4		4	4	4	4
Derivative assets		$ 0						8
Derivative liabilities		3						2
Designated as Hedges [Member] | Fair Value Hedging [Member] | Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		$ 9,000						8,000
Derivative, number of outstanding derivative contracts (in transactions) | transactions		12		12	12	12	12
Derivative assets		$ 0						5
Derivative liabilities		1						0
Not Designated as Hedges [Member] | Foreign Exchange Forward Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		$ 34	[3]	£ 12	$ 1	€ 9	₨ 596	33	[3]	£ 12	$ 1	€ 9	₨ 464
Derivative, number of outstanding derivative contracts (in transactions) | transactions		7		7	7	7	7
Derivative assets		$ 0						0
Derivative liabilities		0						0
Not Designated as Hedges [Member] | When-Issued Forward Contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		$ 27						$ 79
Derivative, number of outstanding derivative contracts (in transactions) | transactions		1		1	1	1	1	1		1	1	1	1
[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 September 30, 2019 , the Company had one outstanding contract with a notional amount of $27 million and immaterial fair value. At December 31, 2018 , the Company had one outstanding contract with a notional amount of $79 million
[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 9 million , GBP 12 million , SGD 1 million and INR 596 million as of September 30, 2019 and notional amounts of EUR 9 million , GBP 12 million , SGD 1 million and INR 464 million as of December 31, 2018 .

Derivatives and Hedging Activ_5

Derivatives and Hedging Activities Derivatives and Hedging Activities (Schedule of Hedged Items in a Fair Value Hedging Relationship) (Details) - Long-term Borrowings [Member] - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Schedule of Hedged Items in Fair Value Hedging Relationship [Line Items]
Carrying amount of hedged assets/liabilities	$ 9,046	$ 7,893
Cumulative amount of fair value hedging adjustment increasing (decreasing) the carrying amount of hedged assets/liabilities	$ 69	$ (91)

Derivatives and Hedging Activ_6

Derivatives and Hedging Activities (Schedule of Impact of the Derivative Instruments on Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Amounts reclassified from OCI into earnings, cash flow hedges	$ 2	$ 2	$ 7	$ 2
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	(407)	(329)	(1,194)	(878)
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	1	0	3	(1)
Gains (losses) on hedged items, fair value hedges	0	0	0	0
Gains (losses) on interest rate swaps, fair value hedges	0	0	0	0
Total gains (losses) on fair value hedges	0	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	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	(231)	(229)	(721)	(656)
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	1	2	4	3
Gains (losses) on hedged items, fair value hedges	(20)	2	(160)	61
Gains (losses) on interest rate swaps, fair value hedges	12	(14)	128	(88)
Total gains (losses) on fair value hedges	(8)	(12)	(32)	(27)
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	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	23	20	73	73
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	0
Gains (losses) on hedged items, fair value hedges	0	0	0	0
Gains (losses) on interest rate swaps, fair value hedges	0	0	0	0
Total gains (losses) on fair value hedges	0	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	$ 1	$ 2

Segment Disclosures (Narrative)

Segment Disclosures (Narrative) (Details)	9 Months Ended
	Sep. 30, 2019segment
Segment Reporting [Abstract]
Number of reportable segments (in number of segments)	2

Segment Disclosures (Schedule o

Segment Disclosures (Schedule of Segment Disclosures) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Interest income	$ 3,040	$ 2,781	$ 8,954	$ 7,986
Interest expense	638	558	1,915	1,534
Net interest income	2,402	2,223	7,039	6,452
Provision for loan losses	799	742	2,395	2,235
Other income	498	501	1,476	1,450
Other expense	1,107	1,015	3,209	2,967
Income before income tax expense	994	967	2,911	2,700
Other [Member]
Segment Reporting Information [Line Items]
Interest income	122	97	392	249
Credit Card Loans [Member]
Segment Reporting Information [Line Items]
Interest income	2,465	2,258	7,223	6,487
Provision for loan losses	719	633	2,121	1,915
Total Other Loans [Member] | Private Student Loans [Member]
Segment Reporting Information [Line Items]
Interest income	175	154	520	451
Total Other Loans [Member] | Personal Loans [Member]
Segment Reporting Information [Line Items]
Interest income	249	238	727	693
Provision for loan losses	86	87	250	244
PCI Student Loans [Member]
Segment Reporting Information [Line Items]
Interest income	29	34	92	106
Provision for loan losses	0	0	0	0
Operating Segments [Member] | Direct Banking [Member]
Segment Reporting Information [Line Items]
Interest income	3,040	2,781	8,953	7,986
Interest expense	638	558	1,915	1,534
Net interest income	2,402	2,223	7,038	6,452
Provision for loan losses	799	742	2,395	2,235
Other income	409	421	1,217	1,213
Other expense	1,069	979	3,097	2,859
Income before income tax expense	943	923	2,763	2,571
Operating Segments [Member] | Direct Banking [Member] | Other [Member]
Segment Reporting Information [Line Items]
Interest income	122	97	391	249
Operating Segments [Member] | Direct Banking [Member] | Credit Card Loans [Member]
Segment Reporting Information [Line Items]
Interest income	2,465	2,258	7,223	6,487
Operating Segments [Member] | Direct Banking [Member] | Total Other Loans [Member] | Private Student Loans [Member]
Segment Reporting Information [Line Items]
Interest income	175	154	520	451
Operating Segments [Member] | Direct Banking [Member] | Total Other Loans [Member] | Personal Loans [Member]
Segment Reporting Information [Line Items]
Interest income	249	238	727	693
Operating Segments [Member] | Direct Banking [Member] | PCI Student Loans [Member]
Segment Reporting Information [Line Items]
Interest income	29	34	92	106
Operating Segments [Member] | Payment Services [Member]
Segment Reporting Information [Line Items]
Interest income	0	0	1	0
Interest expense	0	0	0	0
Net interest income	0	0	1	0
Provision for loan losses	0	0	0	0
Other income	89	80	259	237
Other expense	38	36	112	108
Income before income tax expense	51	44	148	129
Operating Segments [Member] | Payment Services [Member] | Other [Member]
Segment Reporting Information [Line Items]
Interest income	0	0	1	0
Operating Segments [Member] | Payment Services [Member] | Credit Card Loans [Member]
Segment Reporting Information [Line Items]
Interest income	0	0	0	0
Operating Segments [Member] | Payment Services [Member] | Total Other Loans [Member] | Private Student Loans [Member]
Segment Reporting Information [Line Items]
Interest income	0	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	0
Operating Segments [Member] | Payment Services [Member] | PCI Student Loans [Member]
Segment Reporting Information [Line Items]
Interest income	$ 0	$ 0	$ 0	$ 0

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		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Discount and interchange revenue, net		$ 255	$ 280	$ 785	$ 797
Protection products revenue		48	51	146	154
Transaction processing revenue		52	47	146	132
Other income subject to ASC 606		23	20	73	73
Loan fee income		120	103	326	294
Total other income not subject to ASC 606		120	103	326	294
Total other income by operating segment		498	501	1,476	1,450
Customer rewards included in discount and interchange revenue		520	473	1,400	1,300
Deposit product fees reported in net interest income and excluded from other income subject to ASC 606			1	2	2
Accounting Standards Update 2014-09 [Member]
Disaggregation of Revenue [Line Items]
Discount and interchange revenue, net	[1]	255	280	785	797
Protection products revenue		48	51	146	154
Transaction processing revenue		52	47	146	132
Other income subject to ASC 606		23	20	73	73
Total other income subject to ASC 606	[2]	378	398	1,150	1,156
Operating Segments [Member] | Direct Banking [Member]
Disaggregation of Revenue [Line Items]
Loan fee income		120	103	326	294
Total other income not subject to ASC 606		120	103	326	294
Total other income by operating segment		409	421	1,217	1,213
Operating Segments [Member] | Direct Banking [Member] | Accounting Standards Update 2014-09 [Member]
Disaggregation of Revenue [Line Items]
Discount and interchange revenue, net	[1]	238	266	738	758
Protection products revenue		48	51	146	154
Transaction processing revenue		0	0	0	0
Other income subject to ASC 606		3	1	7	7
Total other income subject to ASC 606	[2]	289	318	891	919
Operating Segments [Member] | Payment Services [Member]
Disaggregation of Revenue [Line Items]
Loan fee income		0	0	0	0
Total other income not subject to ASC 606		0	0	0	0
Total other income by operating segment		89	80	259	237
Operating Segments [Member] | Payment Services [Member] | Accounting Standards Update 2014-09 [Member]
Disaggregation of Revenue [Line Items]
Discount and interchange revenue, net	[1]	17	14	47	39
Protection products revenue		0	0	0	0
Transaction processing revenue		52	47	146	132
Other income subject to ASC 606		20	19	66	66
Total other income subject to ASC 606	[2]	$ 89	$ 80	$ 259	$ 237
[1]	Net of rewards, including Cashback Bonus rewards, of $520 million and $473 million for the three months ended September 30, 2019 and 2018 , respectively, and $1.4 billion and $1.3 billion for the nine months ended September 30, 2019 and 2018 , respectively.
[2]	Excludes $2 million of deposit product fees that are reported within net interest income for the nine months ended September 30, 2019 and 2018 and $1 million for the three months ended September 30, 2018 . Deposit product fees were immaterial for the three months ended September 30, 2019 .