SLM (SLM) 10-Q 22 Oct 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information	9 Months Ended
	Sep. 30, 2018shares
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Trading Symbol	SLM
Entity Registrant Name	SLM Corporation
Entity Central Index Key	1,032,033
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)	435,661,454
Entity Emerging Growth Company	false
Entity Small Business	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Assets
Cash and cash equivalents	$ 1,839,054	$ 1,534,339
Available-for-sale investments at fair value (cost of $181,785 and $247,607, respectively)	172,370	244,088
Loans held for investment (net of allowance for losses of $328,974 and $251,475, respectively)	21,978,903	18,567,641
Restricted cash	115,658	101,836
Other interest-earning assets	32,071	21,586
Accrued interest receivable	1,270,026	967,482
Premises and equipment, net	105,058	89,748
Income taxes receivable, net	22,102	0
Tax indemnification receivable	54,941	168,011
Other assets	101,000	84,853
Total assets	25,691,183	21,779,584
Liabilities
Deposits	17,873,293	15,505,383
Long-term borrowings	4,532,221	3,275,270
Income taxes payable, net	0	102,285
Upromise member accounts	226,176	243,080
Other liabilities	219,158	179,310
Total liabilities	22,850,848	19,305,328
Commitments and contingencies
Equity
Preferred stock, par value $0.20 per share, 20 million shares authorized: Series B: 4 million and 4 million shares issued, respectively, at stated value of $100 per share	400,000	400,000
Common stock, par value $0.20 per share, 1.125 billion shares authorized: 449.8 million and 443.5 million shares issued, respectively	89,962	88,693
Additional paid-in capital	1,268,763	1,222,277
Accumulated other comprehensive income (net of tax expense of $8,666 and $1,696, respectively)	27,012	2,748
Retained earnings	1,196,895	868,182
Total SLM Corporation stockholders’ equity before treasury stock	2,982,632	2,581,900
Less: Common stock held in treasury at cost: 14.1 million and 11.1 million shares, respectively	(142,297)	(107,644)
Total equity	2,840,335	2,474,256
Total liabilities and equity	$ 25,691,183	$ 21,779,584

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Amortized cost	$ 181,785	$ 247,607
Allowance for loan losses	328,974	251,475
Tax expense for accumulated other comprehensive (loss) income	$ 8,666	$ 1,696
Preferred stock, stated value (in dollars per share)	$ 0.20	$ 0.20
Preferred stock shares authorized (in shares)	20,000,000	20,000,000
Common stock par value (in dollars per share)	$ 0.20	$ 0.20
Common stock, shares authorized (in shares)	1,125,000,000	1,125,000,000
Common stock shares issued (in shares)	449,800,000	443,500,000
Common stock held in treasury (in shares)	14,100,000	11,100,000
Series B Preferred Stock
Preferred stock, stated value (in dollars per share)	$ 100	$ 100
Preferred stock shares outstanding (in shares)	4,000,000	4,000,000

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Interest income:
Loans	$ 485,997	$ 359,610	$ 1,370,090	$ 1,021,106
Investments	1,340	1,928	4,981	6,272
Cash and cash equivalents	10,260	4,686	22,068	10,429
Total interest income	497,597	366,224	1,397,139	1,037,807
Interest expense:
Deposits	105,093	61,890	273,154	157,473
Interest expense on short-term borrowings	1,156	1,804	4,677	4,234
Interest expense on long-term borrowings	34,715	20,469	89,111	56,070
Total interest expense	140,964	84,163	366,942	217,777
Net interest income	356,633	282,061	1,030,197	820,030
Less: provisions for credit losses	70,047	54,930	187,245	130,441
Net interest income after provisions for credit losses	286,586	227,131	842,952	689,589
Non-interest (loss) income:
Gains on sales of loans, net	0	0	2,060	0
Losses on sales of securities, net	0	0	(1,549)	0
(Losses) gains on derivatives and hedging activities, net	(4,949)	1,661	(6,325)	(7,326)
Other (loss) income	(80,702)	4,455	(58,765)	26,430
Total non-interest (loss) income	(85,651)	6,116	(64,579)	19,104
Non-interest expenses:
Compensation and benefits	62,260	51,052	190,822	157,523
FDIC assessment fees	9,136	7,626	25,933	21,477
Other operating expenses	79,236	57,464	193,974	151,070
Total operating expenses	150,632	116,142	410,729	330,070
Acquired intangible asset amortization expense	92	117	276	351
Total non-interest expenses	150,724	116,259	411,005	330,421
Income before income tax (benefit) expense	50,211	116,988	367,368	378,272
Income tax (benefit) expense	(53,667)	40,617	27,404	136,341
Net income	103,878	76,371	339,964	241,931
Preferred stock dividends	4,124	3,028	11,441	12,577
Net income attributable to SLM Corporation common stock	$ 99,754	$ 73,343	$ 328,523	$ 229,354
Basic earnings per common share attributable to SLM Corporation (in dollars per share)	$ 0.23	$ 0.17	$ 0.76	$ 0.53
Average common shares outstanding (in shares)	435,468	431,718	434,875	430,958
Diluted earnings per common share attributable to SLM Corporation (in dollars per share)	$ 0.23	$ 0.17	$ 0.75	$ 0.52
Average common and common equivalent shares outstanding (in shares)	440,019	438,419	439,484	438,422

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 103,878	$ 76,371	$ 339,964	$ 241,931
Other comprehensive income (loss):
Unrealized (losses) gains on investments	(1,811)	734	(5,896)	(666)
Unrealized gains on cash flow hedges	6,556	4,814	36,860	7,564
Total unrealized gains	4,745	5,548	30,964	6,898
Income tax expense	(1,219)	(2,113)	(7,562)	(2,644)
Other comprehensive income, net of tax expense	3,526	3,435	23,402	4,254
Total comprehensive income	$ 107,404	$ 79,806	$ 363,366	$ 246,185

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands	Total	Series A Preferred Stock	Series B Preferred Stock	Preferred Stock	Preferred StockSeries A Preferred Stock	Common Stock	Treasury Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Retained EarningsSeries A Preferred Stock	Retained EarningsSeries B Preferred Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of adoption of accounting principle	$ 165							$ 429		$ (264)
Beginning Balance (in shares) at Dec. 31, 2016				7,300,000		428,903,559	7,728,920
Beginning Balance, shares issued (in shares) at Dec. 31, 2016						436,632,479
Beginning Balance at Dec. 31, 2016	2,347,058			$ 565,000		$ 87,327	$ (67,484)	1,175,564	$ (8,671)	595,322
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	241,931									241,931
Other comprehensive income, net of tax	4,254								4,254
Total comprehensive income	$ 246,185
Cash dividends:
Cash dividends		$ (3,961)	$ (8,616)								$ (3,961)	$ (8,616)
Redemption of Series A Preferred Stock (in shares)					(3,300,000)
Redemption of Series A Preferred Stock		$ (165,000)			$ (165,000)
Dividend equivalent units related to employee stock-based compensation plans								96		(96)
Issuance of common shares (in shares)	5,652,886					5,652,886
Issuance of common shares	$ 16,467					$ 1,131		15,336
Stock-based compensation expense	$ 21,773							21,773
Shares repurchased related to employee stock-based compensation plans (in shares)	(2,666,781)					(2,666,781)	(2,666,781)
Shares repurchased related to employee stock-based compensation plans	$ (32,231)						$ (32,231)
Ending Balance (in shares) at Sep. 30, 2017				4,000,000		431,889,664	10,395,701
Ending Balance, shares issued (in shares) at Sep. 30, 2017						442,285,365
Ending Balance at Sep. 30, 2017	2,421,840			$ 400,000		$ 88,458	$ (99,715)	1,213,198	(4,417)	824,316
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of adoption of accounting principle | Accounting Standards Update 2017-12	1,052								270	782
Beginning Balance (in shares) at Dec. 31, 2017				4,000,000		432,376,250	11,087,337
Beginning Balance, shares issued (in shares) at Dec. 31, 2017						443,463,587
Beginning Balance at Dec. 31, 2017	2,474,256			$ 400,000		$ 88,693	$ (107,644)	1,222,277	2,748	868,182
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	339,964									339,964
Other comprehensive income, net of tax	23,402								23,402
Total comprehensive income	$ 363,366
Reclassification resulting from the adoption of ASU No. 2018-02									592	(592)
Cash dividends:
Cash dividends			$ (11,441)									$ (11,441)
Issuance of common shares (in shares)	6,341,950					6,341,950
Issuance of common shares	$ 21,927					$ 1,269		20,658
Stock-based compensation expense	$ 25,828							25,828
Shares repurchased related to employee stock-based compensation plans (in shares)	(3,056,746)					(3,056,746)	(3,056,746)
Shares repurchased related to employee stock-based compensation plans	$ (34,653)						$ (34,653)
Ending Balance (in shares) at Sep. 30, 2018				4,000,000		435,661,454	14,144,083
Ending Balance, shares issued (in shares) at Sep. 30, 2018						449,805,537
Ending Balance at Sep. 30, 2018	$ 2,840,335			$ 400,000		$ 89,962	$ (142,297)	$ 1,268,763	$ 27,012	$ 1,196,895

CONSOLIDATED STATEMENTS OF CH_2

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Parenthetical) - $ / shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Series A Preferred Stock
Preferred stock dividend rate (in dollars per share)		$ 1.74
Series B Preferred Stock
Preferred stock dividend rate (in dollars per share)	$ 2.86	$ 2.15

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating activities
Net income	$ 339,964	$ 241,931
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Provisions for credit losses	187,245	130,441
Income tax expense	27,404	136,341
Amortization of brokered deposit placement fee	9,378	6,831
Amortization of ABCP Facility upfront fee	851	995
Amortization of deferred loan origination costs and loan premium/(discounts), net	8,039	6,122
Net amortization of discount on investments	1,344	1,504
Reduction of tax indemnification receivable	86,079	311
Depreciation of premises and equipment	9,977	8,194
Amortization of acquired intangibles	276	351
Stock-based compensation expense	25,828	21,773
Unrealized losses on derivatives and hedging activities, net	6,065	6,931
Gains on sales of loans, net	(2,060)	0
Losses on sales of securities, net	1,549	0
Other adjustments to net income, net	5,428	4,601
Changes in operating assets and liabilities:
Increase in accrued interest receivable	(628,959)	(506,451)
(Increase) decrease in other interest-earning assets	(10,485)	17,811
Decrease in tax indemnification receivable	26,991	44,725
Increase in other assets	(60,903)	(53,275)
Decrease in income taxes payable, net	(156,502)	(217,235)
Increase in accrued interest payable	27,265	15,240
Decrease in payable due to entity that is a subsidiary of Navient	(676)	(305)
Increase in other liabilities	3,502	6,143
Total adjustments	(432,364)	(368,952)
Total net cash used in operating activities	(92,400)	(127,021)
Investing activities
Loans acquired and originated	(5,570,195)	(4,314,711)
Net proceeds from sales of loans held for investment	44,832	5,497
Proceeds from claim payments	38,492	34,759
Net decrease in loans held for investment	2,208,681	1,488,087
Purchases of available-for-sale securities	(7,914)	(55,569)
Proceeds from sales and maturities of available-for-sale securities	70,843	29,452
Total net cash used in investing activities	(3,215,261)	(2,812,485)
Financing activities
Brokered deposit placement fee	(25,104)	(9,668)
Net increase in certificates of deposit	1,953,644	1,087,486
Net increase in other deposits	458,472	516,343
Borrowings collateralized by loans in securitization trusts - issued	1,890,912	767,245
Borrowings collateralized by loans in securitization trusts - repaid	(639,190)	(397,106)
Issuance costs for unsecured debt offering	0	(1,057)
Unsecured debt issued	0	197,000
Borrowings under ABCP Facility	300,000	300,000
Repayment of borrowings under ABCP Facility	(300,000)	0
Fees paid on ABCP Facility	(1,095)	(1,281)
Redemption of Preferred Stock Series A	0	(165,000)
Preferred stock dividends paid	(11,441)	(12,577)
Net cash provided by financing activities	3,626,198	2,281,385
Net increase (decrease) in cash, cash equivalents and restricted cash	318,537	(658,121)
Cash, cash equivalents and restricted cash at beginning of period	1,636,175	1,972,510
Cash, cash equivalents and restricted cash at beginning of period	1,954,712	1,314,389
Cash disbursements made for:
Interest	327,798	191,488
Income taxes paid	161,248	216,321
Income taxes refunded	(5,174)	(986)
Reconciliation of the Consolidated Statements of Cash Flows to the Consolidated Balance Sheets:
Total cash, cash equivalents and restricted cash	$ 1,636,175	$ 1,972,510

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies Basis of Presentation The accompanying unaudited, consolidated financial statements of SLM Corporation (“Sallie Mae,” “SLM,” the “Company,” “we,” or “us”) have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) for interim financial information. Accordingly, they do not include all the information and footnotes required by GAAP for complete consolidated financial statements. The consolidated financial statements include the accounts of SLM Corporation and its majority-owned and controlled subsidiaries after eliminating the effects of intercompany accounts and transactions. In the opinion of management, all adjustments considered necessary for a fair statement of the results for the interim periods have been included. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. Operating results for the three and nine months ended September 30, 2018 are not necessarily indicative of the results for the year ending December 31, 2018 or for any other period. These unaudited financial statements should be read in conjunction with the audited financial statements and related notes included in our Annual Report on Form 10-K for the year ended December 31, 2017 (the “2017 Form 10-K”). Consolidation The consolidated financial statements include the accounts of the Company and its majority-owned and controlled subsidiaries after eliminating the effects of intercompany accounts and transactions. We consolidate any variable interest entity (“VIE”) where we have determined we are the primary beneficiary. The primary beneficiary is the entity which has both: (1) the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance and (2) the obligation to absorb losses or receive benefits of the entity that could potentially be significant to the VIE. Recently Issued and Adopted Accounting Pronouncements ASU No. 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash” In November 2016, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) No. 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash.” Whereas restricted cash balances have traditionally been excluded from the statement of cash flows, this ASU requires restricted cash and restricted cash equivalents to be included within the beginning and ending totals of cash, cash equivalents and restricted cash presented on the statement of cash flows for all periods presented. Restricted cash and restricted cash equivalent inflows and outflows with external parties are required to be classified within the operating, investing, and/or financing activity sections of the statement of cash flows, whereas transfers between cash and cash equivalents and restricted cash and restricted cash equivalents should no longer be presented on the statement of cash flows. ASU No. 2016-18 also requires (a) the nature of the restrictions to be disclosed to help provide information about the sources and uses of these balances during a reporting period and (b) a reconciliation of the cash, cash equivalents and restricted cash totals on the statement of cash flows to the related balance sheet line items when cash, cash equivalents, and restricted cash are presented in more than one line item on the balance sheet. The reconciliation can be presented either on the face of the statement of cash flows or in the notes to the financial statements and must be provided for each period that a balance sheet is presented. We adopted the new accounting pronouncement on January 1, 2018, and the adoption did not have a material impact to our statement of cash flows. ASU No. 2017-12, “Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities” On August 28, 2017, the FASB issued ASU No. 2017-12, “Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities,” which (a) improves the financial reporting of hedging relationships to better portray the economic results of an entity's risk management activities in its financial statements and (b) makes certain targeted improvements to simplify the application of the hedge accounting guidance. The effective date for the standard is January 1, 2019, with early adoption permitted. We elected to early adopt the standard effective July 1, 2018. One of the key changes is that the standard eliminates the separate measurement and reporting of hedge ineffectiveness. In accordance with the new standard, certain provisions were required to be applied on a modified retrospective basis, which requires a cumulative effect adjustment to accumulated other comprehensive income with a corresponding adjustment to retained earnings as of the beginning of the fiscal year of adoption, or January 1, 2018 in our case. The accounting for derivative instruments requires that every derivative instrument, including certain derivative instruments embedded in other contracts, be recorded on the balance sheet as either an asset or liability measured at fair value. Our derivative instruments are classified and accounted for by us as fair value hedges, cash flow hedges, or trading hedges. Fair Value Hedges We generally use fair value hedges to offset the exposure to changes in fair value of a recognized fixed-rate liability. We enter into interest rate swaps to economically convert fixed-rate liabilities into variable-rate liabilities. For fair value hedges, we generally consider all components of the derivative’s gain and/or loss when assessing hedge effectiveness and generally hedge changes in fair values due to interest rates. Under the new standard, for fair value hedges, the entire change in the fair value of the hedging instrument included in the assessment of hedge effectiveness is recorded in the same line item in the consolidated statements of income that is used to present the earnings effect of the hedged component of the hedged item. The timing of recognition of the change in fair value of a hedging instrument included in the assessment of hedge effectiveness is the same as prior to the adoption of ASU No. 2017-12. Cash Flow Hedges We use cash flow hedges to hedge the exposure to variability in cash flows of floating-rate liabilities. This strategy is used primarily to minimize the exposure to volatility in cash flows from future changes in interest rates. In assessing hedge effectiveness, generally all components of each derivative’s gains or losses are included in the assessment. We hedge exposure to changes in cash flows due to changes in interest rates or total changes in cash flow. Under the new standard, for cash flow hedges, the entire change in the fair value of the hedging instrument included in the assessment of hedge effectiveness is recorded in other comprehensive income (loss). Those amounts are subsequently reclassified to earnings, in the same line item in the consolidated statements of income as impacted by the hedged item, when the hedged item affects earnings. Amounts reported in accumulated other comprehensive income related to derivatives will be reclassified to interest expense as interest payments are made on our variable-rate deposits. During the next twelve months, we estimate that $7 million will be reclassified as an increase to interest expense. Trading Activities When derivative instruments do not qualify for hedge accounting treatment, they are accounted for at fair value with all changes in fair value recorded through earnings. All of our derivative instruments with maturities of less than 3 years are economically hedging risk, but do not receive hedge accounting treatment. Trading derivatives also include any hedges that originally received hedge accounting treatment, but lost hedge accounting treatment due to failed effectiveness testing, as well as the activity of certain derivatives prior to those derivatives receiving hedge accounting treatment. Cumulative effect of applying the new standard As a result of the cumulative effect of applying the new hedging standard to our fair value hedges on July 1, 2018, we recorded a $2.0 million basis increase to our hedged deposit balances with a corresponding increase to retained earnings of approximately $1.0 million and a $3.0 million loss to “gains (losses) on derivatives and hedging activities, net” in our consolidated statements of income to adjust the life-to-date ineffectiveness. To reflect the adoption of the new hedging standard on our cash flow hedging relationships at July 1, 2018, we recorded a $0.3 million decrease to retained earnings and a corresponding $0.3 million increase to accumulated other comprehensive income. The new standard also requires modifications to existing presentation and disclosure requirements. We did not apply adjustments to our prior period consolidated balance sheets or consolidated statements of income as a result of adopting the new hedging standard. However, certain disclosures within the notes to the financial statements set forth in this report, regarding the three and nine month periods ended September 30, 2017, conform to the disclosure requirements of ASU No. 2017-12. For further details, refer to Note 7, “Derivative Financial Instruments.” ASU No. 2018-02, “Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income” In February 2018, the FASB issued ASU No. 2018-02, “Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income,” which allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the tax law and tax rate changes under the Tax Cuts and Jobs Act of 2017 (the “Tax Act”) enacted on December 22, 2017. Under the Tax Act, deferred taxes were adjusted to reflect the reduction of the historical corporate income tax rate to the newly enacted corporate income tax rate, which left the tax effects on items within accumulated other comprehensive income stranded at an inappropriate tax rate. This guidance is effective for fiscal years beginning after December 15, 2018, and for interim periods within those fiscal years, with early adoption permitted. We adopted this standard effective January 1, 2018 and recorded a $0.6 million

Investments

Investments	9 Months Ended
	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Investments	Investments The amortized cost and fair value of securities available for sale are as follows: September 30, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Available for sale: Mortgage-backed securities $ 159,397 $ 92 $ (8,046 ) $ 151,443 Utah Housing Corporation bonds 22,388 — (1,461 ) 20,927 Total $ 181,785 $ 92 $ (9,507 ) $ 172,370 December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Available for sale: Mortgage-backed securities $ 227,607 $ 650 $ (3,210 ) $ 225,047 Utah Housing Corporation bonds 20,000 — (959 ) 19,041 Total $ 247,607 $ 650 $ (4,169 ) $ 244,088 The following table summarizes the amount of gross unrealized losses for our mortgage-backed securities and Utah Housing Corporation bonds and the estimated fair value for securities having gross unrealized losses, categorized by length of time the securities have been in an unrealized loss position: Less than 12 months 12 months or more Total Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value As of September 30, 2018: Mortgage-backed securities $ (1,768 ) $ 43,253 $ (6,278 ) $ 104,841 $ (8,046 ) $ 148,094 Utah Housing Corporation bonds (125 ) 4,875 (1,336 ) 16,052 (1,461 ) 20,927 Total $ (1,893 ) $ 48,128 $ (7,614 ) $ 120,893 $ (9,507 ) $ 169,021 As of December 31, 2017: Mortgage-backed securities $ (772 ) $ 77,356 $ (2,438 ) $ 110,500 $ (3,210 ) $ 187,856 Utah Housing Corporation bonds (77 ) 4,923 (882 ) 14,118 (959 ) 19,041 Total $ (849 ) $ 82,279 $ (3,320 ) $ 124,618 $ (4,169 ) $ 206,897 Our investment portfolio is comprised primarily of mortgage-backed securities issued by Ginnie Mae, Fannie Mae and Freddie Mac, with amortized costs of $68 million , $47 million , and $44 million , respectively, at September 30, 2018. We own these securities to meet our requirements under the Community Reinvestment Act. In the second quarter of 2018, we elected to sell nine securities totaling $41 million to better align the portfolio with the Community Reinvestment Act requirements, and we recognized a $2 million loss upon the sale of those securities. As of September 30, 2018, 75 of the 84 separate mortgage-backed securities in our investment portfolio had unrealized losses, and 35 of the 75 securities in a net loss position were issued under Ginnie Mae programs that carry a full faith and credit guarantee from the U.S. Government. The remaining securities in a net loss position carry a principal and interest guarantee by Fannie Mae or Freddie Mac, respectively. We have the ability and the intent to hold these securities for a period of time sufficient for the market price to recover to at least the adjusted amortized cost of the security. As of December 31, 2017, 62 of the 92 separate mortgage-backed securities in our investment portfolio had unrealized losses, and 31 of the 62 securities in a net loss position were issued under Ginnie Mae programs that carry a full faith and credit guarantee from the U.S. Government. The remainder carried a principal and interest guarantee by Fannie Mae or Freddie Mac, respectively. We also invest in Utah Housing Corporation bonds for the purpose of complying with the Community Reinvestment Act. These bonds are rated Aa3 by Moody’s Investors Service. The amortized cost of the investment on the consolidated balance sheet at September 30, 2018 and December 31, 2017 was $22 million and $20 million , respectively. We have the intent and ability to hold these bonds for a period of time sufficient for the market price to recover to at least the adjusted amortized cost of the security. As of September 30, 2018, the amortized cost and fair value of securities, by contractual maturities, are summarized below. Contractual maturities versus actual maturities may differ due to the effect of prepayments. Year of Maturity Amortized Cost Estimated Fair Value 2038 $ 267 $ 281 2039 2,990 3,068 2042 9,524 8,766 2043 14,396 13,728 2044 23,437 22,535 2045 25,868 24,468 2046 40,006 37,703 2047 57,395 54,082 2048 7,902 7,739 Total $ 181,785 $ 172,370 The mortgage-backed securities have been pledged to the Federal Reserve Bank (the “FRB”) as collateral against any advances and accrued interest under the Primary Credit lending program sponsored by the FRB. We had $ 153 million and $218 million

Loans Held for Investment

Loans Held for Investment	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Loans Held for Investment	Loans Held for Investment Loans held for investment consist of Private Education Loans, FFELP Loans and Personal Loans. We use “Private Education Loans” to mean education loans to students or their families that are not made, insured or guaranteed by any state or federal government. Private Education Loans do not include loans insured or guaranteed under the previously existing Federal Family Education Loan Program (“FFELP”). We use “Personal Loans” to mean those unsecured loans to individuals that may be used for non-educational purposes. We began acquiring Personal Loans from third parties in the fourth quarter of 2016 and originating Personal Loans in the first quarter of 2018. Our Private Education Loans are made largely to bridge the gap between the cost of higher education and the amount funded through financial aid, government loans and customers’ resources. Private Education Loans bear the full credit risk of the customer. We manage this risk through risk-performance underwriting strategies and qualified cosigners. Private Education Loans may be fixed rate or may carry a variable interest rate indexed to LIBOR. As of September 30, 2018 , and December 31, 2017, 69 percent and 77 percent , respectively, of all of our Private Education Loans were indexed to LIBOR. We provide incentives for customers to include a cosigner on the loan, and the vast majority of loans in our portfolio are cosigned. We also encourage customers to make payments while in school. In connection with the separation of Navient Corporation (“Navient”) from SLM (the “Spin-Off”), we retained the right to require Navient to purchase delinquent loans (at fair value) when the borrower has a lending relationship with both us and Navient (“Split Loans”). In the second quarter of 2018, we sold our remaining $43 million portfolio of Split Loans (both current and non-current loans) to Navient and recognized a net gain of $2 million . FFELP Loans are insured as to their principal and accrued interest in the event of default, subject to a risk-sharing level based on the date of loan disbursement. These insurance obligations are supported by contractual rights against the United States. For loans disbursed on or after July 1, 2006, we receive 97 percent reimbursement on all qualifying claims. For loans disbursed after October 1, 1993, and before July 1, 2006, we receive 98 percent reimbursement on all qualifying claims. For loans disbursed prior to October 1, 1993, we receive 100 percent reimbursement on all qualifying claims. Loans held for investment are summarized as follows: September 30, December 31, 2018 2017 Private Education Loans: Fixed rate $ 6,369,950 $ 4,000,447 Variable rate 13,870,041 13,431,720 Total Private Education Loans, gross 20,239,991 17,432,167 Deferred origination costs and unamortized premium/(discount) 65,499 56,378 Allowance for loan losses (274,684 ) (243,715 ) Total Private Education Loans, net 20,030,806 17,244,830 FFELP Loans 866,786 927,660 Deferred origination costs and unamortized premium/(discount) 2,432 2,631 Allowance for loan losses (1,080 ) (1,132 ) Total FFELP Loans, net 868,138 929,159 Personal Loans (fixed rate) 1,133,005 400,280 Deferred origination costs and unamortized premium/(discount) 164 — Allowance for loan losses (53,210 ) (6,628 ) Total Personal Loans, net 1,079,959 393,652 Loans held for investment, net $ 21,978,903 $ 18,567,641 The estimated weighted average life of education loans in our portfolio was approximately 5.4 years and 5.5 years at September 30, 2018 and December 31, 2017 , respectively. The average balance and the respective weighted average interest rates of loans in our portfolio are summarized as follows: Three Months Ended September 30, 2018 2017 Average Balance Weighted Average Interest Rate Average Balance Weighted Average Interest Rate Private Education Loans $ 19,295,318 9.16 % $ 16,228,751 8.50 % FFELP Loans 877,279 4.65 960,185 4.02 Personal Loans 1,082,177 11.03 86,441 9.66 Total portfolio $ 21,254,774 $ 17,275,377 Nine Months Ended September 30, 2018 2017 Average Balance Weighted Average Interest Rate Average Balance Weighted Average Interest Rate Private Education Loans $ 18,908,929 9.01 % $ 15,791,557 8.37 % FFELP Loans 898,208 4.47 981,106 3.86 Personal Loans 810,753 10.82 61,263 9.44 Total portfolio $ 20,617,890 $ 16,833,926

Allowance for Loan Losses

Allowance for Loan Losses	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Allowance for Loan Losses	Allowance for Loan Losses Our provision for credit losses represents the periodic expense of maintaining an allowance sufficient to absorb incurred probable losses in the held-for-investment loan portfolios. The evaluation of the allowance for loan losses is inherently subjective, as it requires material estimates that may be susceptible to significant changes. We believe the allowance for loan losses is appropriate to cover probable losses incurred in the loan portfolios. Allowance for Loan Losses Metrics Allowance for Loan Losses Three Months Ended September 30, 2018 FFELP Loans Private Education Loans Personal Loans Total Allowance for Loan Losses Beginning balance $ 1,073 $ 261,695 $ 32,509 $ 295,277 Total provision 259 42,482 26,155 68,896 Net charge-offs: Charge-offs (252 ) (34,229 ) (5,740 ) (40,221 ) Recoveries — 4,736 286 5,022 Net charge-offs (252 ) (29,493 ) (5,454 ) (35,199 ) Loan sales (1) — — — — Ending Balance $ 1,080 $ 274,684 $ 53,210 $ 328,974 Allowance: Ending balance: individually evaluated for impairment $ — $ 119,643 $ — $ 119,643 Ending balance: collectively evaluated for impairment $ 1,080 $ 155,041 $ 53,210 $ 209,331 Loans: Ending balance: individually evaluated for impairment $ — $ 1,199,493 $ — $ 1,199,493 Ending balance: collectively evaluated for impairment $ 866,786 $ 19,040,498 $ 1,133,005 $ 21,040,289 Net charge-offs as a percentage of average loans in repayment (annualized) (2) 0.15 % 0.88 % 2.03 % Allowance as a percentage of the ending total loan balance 0.12 % 1.36 % 4.70 % Allowance as a percentage of the ending loans in repayment (2) 0.16 % 1.99 % 4.70 % Allowance coverage of net charge-offs (annualized) 1.07 2.33 2.44 Ending total loans, gross $ 866,786 $ 20,239,991 $ 1,133,005 Average loans in repayment (2) $ 681,131 $ 13,351,517 $ 1,072,624 Ending loans in repayment (2) $ 679,110 $ 13,815,415 $ 1,133,005 ____________ (1) Represents fair value adjustments on loans sold. (2) Loans in repayment include loans on which borrowers are making interest only or fixed payments, as well as loans that have entered full principal and interest repayment status after any applicable grace period. Allowance for Loan Losses Three Months Ended September 30, 2017 FFELP Loans Private Education Loans Personal Loans Total Allowance for Loan Losses Beginning balance $ 1,606 $ 205,024 $ 818 $ 207,448 Total provision (73 ) 53,120 800 53,847 Net charge-offs: Charge-offs (181 ) (34,280 ) (220 ) (34,681 ) Recoveries — 4,560 2 4,562 Net charge-offs (181 ) (29,720 ) (218 ) (30,119 ) Loan sales (1) — (1,257 ) — (1,257 ) Ending Balance $ 1,352 $ 227,167 $ 1,400 $ 229,919 Allowance: Ending balance: individually evaluated for impairment $ — $ 100,999 $ — $ 100,999 Ending balance: collectively evaluated for impairment $ 1,352 $ 126,168 $ 1,400 $ 128,920 Loans: Ending balance: individually evaluated for impairment $ — $ 942,561 $ — $ 942,561 Ending balance: collectively evaluated for impairment $ 949,180 $ 16,190,346 $ 132,100 $ 17,271,626 Net charge-offs as a percentage of average loans in repayment (annualized) (2) 0.10 % 1.08 % 0.96 % Allowance as a percentage of the ending total loan balance 0.14 % 1.33 % 1.06 % Allowance as a percentage of the ending loans in repayment (2) 0.20 % 1.99 % 1.06 % Allowance coverage of net charge-offs (annualized) 1.87 1.91 1.60 Ending total loans, gross $ 949,180 $ 17,132,907 $ 132,100 Average loans in repayment (2) $ 734,613 $ 10,971,028 $ 90,850 Ending loans in repayment (2) $ 690,849 $ 11,406,581 $ 132,100 ____________ (1) Represents fair value adjustments on loans sold. (2) Loans in repayment include loans on which borrowers are making interest only or fixed payments, as well as loans that have entered full principal and interest repayment status after any applicable grace period. Allowance for Loan Losses Nine Months Ended September 30, 2018 FFELP Loans Private Education Loans Personal Loans Total Allowance for Loan Losses Beginning balance $ 1,132 $ 243,715 $ 6,628 $ 251,475 Total provision 742 130,616 55,981 187,339 Net charge-offs: Charge-offs (794 ) (113,852 ) (9,812 ) (124,458 ) Recoveries — 15,421 413 15,834 Net charge-offs (794 ) (98,431 ) (9,399 ) (108,624 ) Loan sales (1) — (1,216 ) — (1,216 ) Ending Balance $ 1,080 $ 274,684 $ 53,210 $ 328,974 Allowance: Ending balance: individually evaluated for impairment $ — $ 119,643 $ — $ 119,643 Ending balance: collectively evaluated for impairment $ 1,080 $ 155,041 $ 53,210 $ 209,331 Loans: Ending balance: individually evaluated for impairment $ — $ 1,199,493 $ — $ 1,199,493 Ending balance: collectively evaluated for impairment $ 866,786 $ 19,040,498 $ 1,133,005 $ 21,040,289 Net charge-offs as a percentage of average loans in repayment (annualized) (2) 0.15 % 1.01 % 1.56 % Allowance as a percentage of the ending total loan balance 0.12 % 1.36 % 4.70 % Allowance as a percentage of the ending loans in repayment (2) 0.16 % 1.99 % 4.70 % Allowance coverage of net charge-offs (annualized) 1.02 2.09 4.25 Ending total loans, gross $ 866,786 $ 20,239,991 $ 1,133,005 Average loans in repayment (2) $ 700,679 $ 13,009,704 $ 803,928 Ending loans in repayment (2) $ 679,110 $ 13,815,415 $ 1,133,005 ____________ (1) Represents fair value adjustments on loans sold. (2) Loans in repayment include loans on which borrowers are making interest only or fixed payments, as well as loans that have entered full principal and interest repayment status after any applicable grace period. Allowance for Loan Losses Nine Months Ended September 30, 2017 FFELP Loans Private Education Loans Personal Loans Total Allowance for Loan Losses Beginning balance $ 2,171 $ 182,472 $ 58 $ 184,701 Total provision (161 ) 129,105 1,580 130,524 Net charge-offs: Charge-offs (658 ) (93,235 ) (240 ) (94,133 ) Recoveries — 12,216 2 12,218 Net charge-offs (658 ) (81,019 ) (238 ) (81,915 ) Loan sales (1) — (3,391 ) — (3,391 ) Ending Balance $ 1,352 $ 227,167 $ 1,400 $ 229,919 Allowance: Ending balance: individually evaluated for impairment $ — $ 100,999 $ — $ 100,999 Ending balance: collectively evaluated for impairment $ 1,352 $ 126,168 $ 1,400 $ 128,920 Loans: Ending balance: individually evaluated for impairment $ — $ 942,561 $ — $ 942,561 Ending balance: collectively evaluated for impairment $ 949,180 $ 16,190,346 $ 132,100 $ 17,271,626 Net charge-offs as a percentage of average loans in repayment (annualized) (2) 0.12 % 1.02 % 0.51 % Allowance as a percentage of the ending total loan balance 0.14 % 1.33 % 1.06 % Allowance as a percentage of the ending loans in repayment (2) 0.20 % 1.99 % 1.06 % Allowance coverage of net charge-offs (annualized) 1.54 2.10 4.41 Ending total loans, gross $ 949,180 $ 17,132,907 $ 132,100 Average loans in repayment (2) $ 752,990 $ 10,589,725 $ 62,747 Ending loans in repayment (2) $ 690,849 $ 11,406,581 $ 132,100 ____________ (1) Represents fair value adjustments on loans sold. (2) Loans in repayment include loans on which borrowers are making interest only or fixed payments, as well as loans that have entered full principal and interest repayment status after any applicable grace period. Troubled Debt Restructurings (“TDRs”) All of our loans are collectively assessed for impairment, except for loans classified as TDRs (where we conduct individual assessments of impairment). We modify the terms of loans for certain borrowers when we believe such modifications will increase the collectability of the loan. These modifications generally take the form of a forbearance, a temporary interest rate reduction or an extended repayment plan. The majority of our loans that are considered TDRs involve a temporary forbearance of payments and do not change the contractual interest rate of the loan. When we give a borrower facing financial difficulty an interest rate reduction, we temporarily reduce the rate to 2.0 percent for a two -year period and, in the vast majority of cases, permanently extend the final maturity of the loan. The combination of these two loan term changes helps reduce the monthly payment due from the borrower and increases the likelihood the borrower will remain current during the interest rate modification period as well as when the loan returns to its original contractual interest rate. At September 30, 2018 and September 30, 2017, 7.4 percent and 5.2 percent , respectively, of our loans then currently in full principal and interest repayment status were subject to interest rate reductions made under our rate modification program. Once a loan qualifies for TDR status, it remains a TDR for allowance purposes for the remainder of its life. As of September 30, 2018 , and December 31, 2017 , approximately 58 percent and 66 percent , respectively, of TDRs were classified as such due to their forbearance status. For additional information, see Note 6, “Allowance for Loan Losses” in our 2017 Form 10-K. Within the Private Education Loan portfolio, loans greater than 90 days past due are considered to be nonperforming. FFELP Loans are at least 97 percent guaranteed as to their principal and accrued interest by the federal government in the event of default and, therefore, we do not deem FFELP Loans as nonperforming from a credit risk perspective at any point in their life cycle prior to claim payment and continue to accrue interest on those loans through the date of claim. At September 30, 2018 and December 31, 2017 , all TDR loans had a related allowance recorded. The following table provides the recorded investment, unpaid principal balance and related allowance for our TDR loans. Recorded Investment Unpaid Principal Balance Allowance September 30, 2018 TDR Loans $ 1,220,233 $ 1,199,493 $ 119,643 December 31, 2017 TDR Loans $ 1,007,141 $ 990,351 $ 94,682 The following table provides the average recorded investment and interest income recognized for our TDR loans. Three Months Ended 2018 2017 Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized TDR Loans $ 1,180,206 $ 19,943 $ 877,011 $ 16,517 Nine Months Ended 2018 2017 Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized TDR Loans $ 1,106,946 $ 56,509 $ 772,362 $ 43,084 The following table provides information regarding the loan status and aging of TDR loans. September 30, December 31, 2018 2017 Balance % Balance % TDR loans in in-school/grace/deferment (1) $ 68,848 $ 51,745 TDR loans in forbearance (2) 73,403 69,652 TDR loans in repayment (3) and percentage of each status: Loans current 954,309 90.3 % 774,222 89.1 % Loans delinquent 31-60 days (4) 51,979 4.9 48,377 5.6 Loans delinquent 61-90 days (4) 31,582 3.0 28,778 3.3 Loans delinquent greater than 90 days (4) 19,372 1.8 17,577 2.0 Total TDR loans in repayment 1,057,242 100.0 % 868,954 100.0 % Total TDR loans, gross $ 1,199,493 $ 990,351 _____ (1) Deferment includes customers who have returned to school or are engaged in other permitted educational activities and are not yet required to make payments on the loans (e.g., residency periods for medical students or a grace period for bar exam preparation). (2) Loans for customers who have requested extension of grace period generally during employment transition or who have temporarily ceased making full payments due to hardship or other factors, consistent with established loan program servicing policies and procedures. (3) Loans in repayment include loans on which borrowers are making interest only or fixed payments, as well as loans that have entered full principal and interest repayment status after any applicable grace period. (4) The period of delinquency is based on the number of days scheduled payments are contractually past due. The following table provides the amount of modified loans (which include forbearance and reductions in interest rates) that became TDRs in the periods presented. Additionally, for the periods presented, the table summarizes charge-offs occurring in the TDR portfolio, as well as TDRs for which a payment default occurred in the relevant period presented and within 12 months of the loan first being designated as a TDR. We define payment default as more than 60 days past due for this disclosure. Three Months Ended Three Months Ended Modified Loans (1) Charge-offs Payment- Default Modified Loans (1) Charge-offs Payment- Default TDR Loans $ 101,117 $ 11,090 $ 20,595 $ 168,645 $ 12,227 $ 28,275 Nine Months Ended Nine Months Ended Modified Loans (1) Charge-offs Payment- Default Modified Loans (1) Charge-offs Payment- Default TDR Loans $ 301,769 $ 39,315 $ 68,430 $ 415,341 $ 34,965 $ 77,248 _____ (1) Represents the principal balance of loans that have been modified during the period and resulted in a TDR. Private Education Loan Key Credit Quality Indicators FFELP Loans are at least 97 percent insured and guaranteed as to their principal and accrued interest in the event of default; therefore, there are no key credit quality indicators associated with FFELP Loans. For Private Education Loans, the key credit quality indicators are FICO scores, the existence of a cosigner, the loan status and loan seasoning. The FICO scores are assessed at original approval and periodically refreshed/updated through the loan’s term. The following table highlights the gross principal balance of our Private Education Loan portfolio stratified by key credit quality indicators. Private Education Loans Credit Quality Indicators September 30, 2018 December 31, 2017 Credit Quality Indicators: Balance (1) % of Balance Balance (1) % of Balance Cosigners: With cosigner $ 18,147,180 90 % $ 15,658,539 90 % Without cosigner 2,092,811 10 1,773,628 10 Total $ 20,239,991 100 % $ 17,432,167 100 % FICO at Original Approval (2) : Less than 670 $ 1,373,155 7 % $ 1,153,591 6 % 670-699 3,042,228 15 2,596,959 15 700-749 6,655,405 33 5,714,554 33 Greater than or equal to 750 9,169,203 45 7,967,063 46 Total $ 20,239,991 100 % $ 17,432,167 100 % Seasoning (3) : 1-12 payments $ 5,419,487 27 % $ 4,256,592 24 % 13-24 payments 3,238,910 16 3,229,465 19 25-36 payments 2,533,308 13 2,429,238 14 37-48 payments 1,638,309 8 1,502,327 9 More than 48 payments 1,473,944 7 1,256,813 7 Not yet in repayment 5,936,033 29 4,757,732 27 Total $ 20,239,991 100 % $ 17,432,167 100 % (1) Balance represents gross Private Education Loans. (2) Represents the higher credit score of the cosigner or the borrower. (3) Number of months in active repayment (whether interest only payment, fixed payment, or full principal and interest payment status) for which a scheduled payment was due. The following table provides information regarding the loan status of our Private Education Loans. Loans in repayment include loans making interest only or fixed payments, as well as loans that have entered full principal and interest repayment status after any applicable grace period. Private Education Loans September 30, December 31, 2018 2017 Balance % Balance % Loans in-school/grace/deferment (1) $ 5,936,033 $ 4,757,732 Loans in forbearance (2) 488,543 468,402 Loans in repayment and percentage of each status: Loans current 13,492,029 97.7 % 11,911,128 97.6 % Loans delinquent 31-60 days (3) 198,987 1.4 179,002 1.5 Loans delinquent 61-90 days (3) 82,358 0.6 78,292 0.6 Loans delinquent greater than 90 days (3) 42,041 0.3 37,611 0.3 Total Private Education Loans in repayment 13,815,415 100.0 % 12,206,033 100.0 % Total Private Education Loans, gross 20,239,991 17,432,167 Private Education Loans deferred origination costs and unamortized premium/(discount) 65,499 56,378 Total Private Education Loans 20,305,490 17,488,545 Private Education Loans allowance for losses (274,684 ) (243,715 ) Private Education Loans, net $ 20,030,806 $ 17,244,830 Percentage of Private Education Loans in repayment 68.3 % 70.0 % Delinquencies as a percentage of Private Education Loans in repayment 2.3 % 2.4 % Loans in forbearance as a percentage of Private Education Loans in repayment and forbearance 3.4 % 3.7 % (1) Deferment includes customers who have returned to school or are engaged in other permitted educational activities and are not yet required to make payments on the loans (e.g., residency periods for medical students or a grace period for bar exam preparation). (2) Loans for customers who have requested extension of grace period generally during employment transition or who have temporarily ceased making full payments due to hardship or other factors, consistent with established loan program servicing policies and procedures. (3) The period of delinquency is based on the number of days scheduled payments are contractually past due. Personal Loan Key Credit Quality Indicators For Personal Loans, the key credit quality indicators are FICO scores, loan seasoning and loan status. The FICO scores are assessed at original approval and periodically refreshed/updated through the loan’s term. The following table highlights the gross principal balance of our Personal Loan portfolio stratified by key credit quality indicators. Personal Loans Credit Quality Indicators September 30, 2018 December 31, 2017 Credit Quality Indicators: Balance (1) % of Balance Balance (1) % of Balance FICO at Original Approval: Less than 670 $ 79,769 7 % $ 32,156 8 % 670-699 327,364 29 114,731 29 700-749 520,370 46 182,025 45 Greater than or equal to 750 205,502 18 71,368 18 Total $ 1,133,005 100 % $ 400,280 100 % Seasoning (2) : 0-12 payments $ 1,084,706 96 % $ 400,280 100 % 13-24 payments 48,299 4 — — 25-36 payments — — — — 37-48 payments — — — — More than 48 payments — — — — Total $ 1,133,005 100 % $ 400,280 100 % (1) Balance represents gross Personal Loans. (2) Number of months in active repayment for which a scheduled payment was due. The following table provides information regarding the loan status of our Personal Loans. Personal Loans September 30, December 31, 2018 2017 Balance % Balance % Loans in repayment and percentage of each status: Loans current $ 1,123,597 99.2 % $ 398,988 99.7 % Loans delinquent 31-60 days (1) 4,321 0.4 761 0.2 Loans delinquent 61-90 days (1) 2,804 0.2 340 0.1 Loans delinquent greater than 90 days (1) 2,283 0.2 191 — Total Personal Loans in repayment 1,133,005 100.0 % 400,280 100.0 % Total Personal Loans, gross 1,133,005 400,280 Personal Loans deferred origination costs and unamortized premium/(discount) 164 — Total Personal Loans 1,133,169 400,280 Personal Loans allowance for losses (53,210 ) (6,628 ) Personal Loans, net $ 1,079,959 $ 393,652 Delinquencies as a percentage of Personal Loans in repayment 0.8 % 0.3 % _______ (1) The period of delinquency is based on the number of days scheduled payments are contractually past due. Accrued Interest Receivable The following table provides information regarding accrued interest receivable on our Private Education Loans. The table also discloses the amount of accrued interest on loans greater than 90 days past due as compared to our allowance for uncollectible interest. The allowance for uncollectible interest exceeds the amount of accrued interest on our 90 days past due Private Education Loan portfolio for all periods presented. Private Education Loans Accrued Interest Receivable Total Interest Receivable Greater Than 90 Days Past Due Allowance for Uncollectible Interest September 30, 2018 $ 1,250,288 $ 1,594 $ 6,462 December 31, 2017 $ 951,138 $ 1,372 $ 4,664

Deposits

Deposits	9 Months Ended
	Sep. 30, 2018
Banking and Thrift [Abstract]
Deposits	Deposits The following table summarizes total deposits at September 30, 2018 and December 31, 2017 . September 30, December 31, 2018 2017 Deposits - interest bearing $ 17,872,781 $ 15,504,330 Deposits - non-interest bearing 512 1,053 Total deposits $ 17,873,293 $ 15,505,383 Our total deposits of $ 17.9 billion were comprised of $ 9.5 billion in brokered deposits and $ 8.4 billion in retail and other deposits at September 30, 2018 , compared to total deposits of $15.5 billion , which were comprised of $8.2 billion in brokered deposits and $7.3 billion in retail and other deposits, at December 31, 2017. Interest bearing deposits as of September 30, 2018 and December 31, 2017 consisted of retail and brokered non-maturity savings deposits, retail and brokered non-maturity money market deposits (“MMDAs”) and retail and brokered certificates of deposit (“CDs”). Interest bearing deposits include deposits from Educational 529 and Health Savings plans that diversify our funding sources and additional deposits we consider to be core. These and other large omnibus accounts, aggregating the deposits of many individual depositors, represented $5.6 billion of our deposit total as of September 30, 2018 , compared with $ 5.5 billion at December 31, 2017. Some of our deposit products are serviced by third-party providers. Placement fees associated with the brokered CDs are amortized into interest expense using the effective interest rate method. We recognized placement fee expense of $ 4 million and $3 million in the three months ended September 30, 2018 and 2017, respectively, and placement fee expense of $ 9 million and $ 7 million in the nine months ended September 30, 2018 and 2017, respectively. Fees paid to third-party brokers related to brokered CDs were $ 6 million and $4 million for the three months ended September 30, 2018 and 2017, respectively, and fees paid to third-party brokers related to brokered CDs were $ 25 million and $10 million for the nine months ended September 30, 2018 and 2017, respectively. Interest bearing deposits at September 30, 2018 and December 31, 2017 are summarized as follows: September 30, 2018 December 31, 2017 Amount Qtr.-End Weighted Average Stated Rate (1) Amount Year-End Weighted Average Stated Rate (1) Money market $ 8,239,595 2.29 % $ 7,731,966 1.80 % Savings 684,298 1.70 738,243 1.10 Certificates of deposit 8,948,888 2.65 7,034,121 1.93 Deposits - interest bearing $ 17,872,781 $ 15,504,330 ____________ (1) Includes the effect of interest rate swaps in effective hedge relationships. As of September 30, 2018 , and December 31, 2017 , there were $ 420 million and $396 million, respectively, of deposits exceeding Federal Deposit Insurance Corporation (“FDIC”) insurance limits. Accrued interest on deposits was $52 million and $28 million at September 30, 2018 and December 31, 2017

Borrowings

Borrowings	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Borrowings	Borrowings Outstanding borrowings consist of unsecured debt and secured borrowings issued through our term asset-backed securitization (“ABS”) program and our asset-backed commercial paper (“ABCP”) funding facility (the “ABCP Facility”). The following table summarizes our borrowings at September 30, 2018 and December 31, 2017 . September 30, 2018 December 31, 2017 Short-Term Long-Term Total Short-Term Long-Term Total Unsecured borrowings: Unsecured debt $ — $ 197,146 $ 197,146 $ — $ 196,539 $ 196,539 Total unsecured borrowings — 197,146 197,146 — 196,539 196,539 Secured borrowings: Private Education Loan term securitizations: Fixed rate — 2,337,004 2,337,004 — 1,565,760 1,565,760 Variable rate — 1,998,071 1,998,071 — 1,512,971 1,512,971 Total Private Education Loan term securitizations — 4,335,075 4,335,075 — 3,078,731 3,078,731 ABCP Facility — — — — — — Total secured borrowings — 4,335,075 4,335,075 — 3,078,731 3,078,731 Total $ — $ 4,532,221 $ 4,532,221 $ — $ 3,275,270 $ 3,275,270 Short-term Borrowings Asset-Backed Commercial Paper Funding Facility On February 21, 2018, we amended and extended the maturity of our $750 million ABCP Facility. We hold 100 percent of the residual interest in the ABCP Facility trust. Under the amended ABCP Facility, we incur financing costs of between 0.35 percent and 0.45 percent on unused borrowing capacity and approximately 3-month LIBOR plus 0.85 percent on outstandings. The amended ABCP Facility extends the revolving period, during which we may borrow, repay and reborrow funds, until February 20, 2019. The scheduled amortization period, during which amounts outstanding under the ABCP Facility must be repaid, ends on February 20, 2020 (or earlier, if certain material adverse events occur). At both September 30, 2018 and December 31, 2017, there were no borrowings outstanding under the ABCP Facility. We expect to amend and extend the ABCP Facility on an annual basis. Long-term Borrowings Unsecured Debt On April 5, 2017, we issued an unsecured debt offering of $200 million of 5.125 percent Senior Notes due April 5, 2022 at par. At September 30, 2018, the outstanding balance was $197 million . Secured Financings On March 21, 2018, we executed our $670 million SMB Private Education Loan Trust 2018-A term ABS transaction, which was accounted for as a secured financing. We sold $670 million of notes to third parties and retained a 100 percent interest in the residual certificates issued in the securitization, raising approximately $668 million of gross proceeds. The Class A and Class B notes had a weighted average life of 4.43 years and priced at a weighted average LIBOR equivalent cost of 1-month LIBOR plus 0.78 percent . At September 30, 2018, $661 million of our Private Education Loans were encumbered because of this transaction. On June 20, 2018, we executed our $687 million SMB Private Education Loan Trust 2018-B term ABS transaction, which was accounted for as a secured financing. We sold $687 million of notes to third parties and retained a 100 percent interest in the residual certificates issued in the securitization, raising approximately $683 million of gross proceeds. The Class A and Class B notes had a weighted average life of 4.40 years and priced at a weighted average LIBOR equivalent cost of 1-month LIBOR plus 0.76 percent . At September 30, 2018, $692 million of our Private Education Loans were encumbered because of this transaction. On September 19, 2018, we executed our $ 544 million SMB Private Education Loan Trust 2018-C term ABS transaction, which was accounted for as a secured financing. We sold $ 544 million of notes to third parties and retained a 100 percent interest in the residual certificates issued in the securitization, raising approximately $ 541 million of gross proceeds. The Class A and Class B notes had a weighted average life of 4.32 years and priced at a weighted average LIBOR equivalent cost of 1-month LIBOR plus 0.77 percent. At September 30, 2018, $ 555 million of our Private Education Loans were encumbered because of this transaction. Secured Financings at Issuance Issue Date Issued Total Issued Weighted Average Cost of Funds (1) Weighted Average Life (in years) Private Education: 2016-A May 2016 $ 501,000 1-month LIBOR plus 1.38% 4.01 2016-B July 2016 607,000 1-month LIBOR plus 1.36% 4.01 2016-C October 2016 674,000 1-month LIBOR plus 1.15% 4.27 Total notes issued in 2016 $ 1,782,000 Total loan and accrued interest amount securitized at inception in 2016 $ 2,107,042 2017-A February 2017 $ 772,000 1-month LIBOR plus 0.93% 4.27 2017-B November 2017 676,000 1-month LIBOR plus 0.80% 4.07 Total notes issued in 2017 $ 1,448,000 Total loan and accrued interest amount securitized at inception in 2017 $ 1,606,804 2018-A March 2018 $ 670,000 1-month LIBOR plus 0.78% 4.43 2018-B June 2018 686,500 1-month LIBOR plus 0.76% 4.40 2018-C September 2018 544,000 1-month LIBOR plus 0.77% 4.32 Total notes issued in 2018 $ 1,900,500 Total loan and accrued interest amount securitized at inception in 2018 $ 2,101,644 ____________ (1) Represents LIBOR equivalent cost of funds for floating and fixed rate bonds, excluding issuance costs. Consolidated Funding Vehicles We consolidate our financing entities that are VIEs as a result of our being the entities’ primary beneficiary. As a result, these financing VIEs are accounted for as secured borrowings. We consolidate the following financing VIEs as of September 30, 2018 and December 31, 2017 , respectively: September 30, 2018 Debt Outstanding Carrying Amount of Assets Securing Debt Outstanding Short-Term Long-Term Total Loans Restricted Cash Other Assets (1) Total Secured borrowings: Private Education Loan term securitizations $ — $ 4,335,075 $ 4,335,075 $ 5,174,592 $ 111,555 $ 381,760 $ 5,667,907 ABCP Facility — — — — — 430 430 Total $ — $ 4,335,075 $ 4,335,075 $ 5,174,592 $ 111,555 $ 382,190 $ 5,668,337 December 31, 2017 Debt Outstanding Carrying Amount of Assets Securing Debt Outstanding Short-Term Long-Term Total Loans Restricted Cash Other Assets (1) Total Secured borrowings: Private Education Loan term securitizations $ — $ 3,078,731 $ 3,078,731 $ 3,691,024 $ 95,966 $ 240,208 $ 4,027,198 ABCP Facility — — — — 1,017 161 1,178 Total $ — $ 3,078,731 $ 3,078,731 $ 3,691,024 $ 96,983 $ 240,369 $ 4,028,376 ____ (1) Other assets primarily represent accrued interest receivable. Other Borrowing Sources We maintain discretionary uncommitted Federal Funds lines of credit with various correspondent banks, which totaled $125 million at September 30, 2018. The interest rate we are charged on these lines of credit is priced at Fed Funds plus a spread at the time of borrowing and is payable daily. We did not utilize these lines of credit in the nine months ended September 30, 2018 or in the year ended December 31, 2017 . We established an account at the FRB to meet eligibility requirements for access to the Primary Credit borrowing facility at the FRB’s Discount Window (the “Window”). The Primary Credit borrowing facility is a lending program available to depository institutions that are in generally sound financial condition. All borrowings at the Window must be fully collateralized. We can pledge to the FRB asset-backed and mortgage-backed securities, as well as FFELP Loans and Private Education Loans, as collateral for borrowings at the Window. Generally, collateral value is assigned based on the estimated fair value of the pledged assets. At September 30, 2018 and December 31, 2017 , the value of our pledged collateral at the FRB totaled $3.1 billion and $2.6 billion, respectively. The interest rate charged to us is the discount rate set by the FRB. We did not utilize this facility in the nine months ended September 30, 2018 or in the year ended December 31, 2017

Derivative Financial Instrument

Derivative Financial Instruments	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Derivative Financial Instruments Accounting for Derivative Instruments We elected to early adopt ASU No. 2017-12 effective July 1, 2018. Under the new standard, we are no longer required to separately measure and report hedge ineffectiveness, which was previously recorded in “gains (losses) on derivatives and hedging activities, net” in our consolidated statements of income. In accordance with the new standard, certain provisions were required to be applied on a modified retrospective basis, which requires a cumulative effect adjustment to accumulated other comprehensive income with a corresponding adjustment to retained earnings as of the beginning of the fiscal year of adoption, or January 1, 2018 in our case. Among other provisions, the new standard required modifications to existing presentation and disclosure requirements. As such, the disclosures for the three and nine month periods ended September 30, 2017 in the “Impact of Derivatives on the Consolidated Statements of Income” table below, conform to the disclosure requirements of ASU No. 2017-12. See Note 1, “Significant Accounting Policies” for additional information related to the adoption of this new standard. Risk Management Strategy We maintain an overall interest rate risk management strategy that incorporates the use of derivative instruments to reduce the economic effect of interest rate changes. Our goal is to manage interest rate sensitivity by modifying the repricing frequency and underlying index characteristics of certain balance sheet assets or liabilities, so any adverse impacts related to movements in interest rates are managed within low to moderate limits. As a result of interest rate fluctuations, hedged balance sheet positions will appreciate or depreciate in market value or create variability in cash flows. Income or loss on the derivative instruments linked to the hedged item will generally offset the effect of this unrealized appreciation or depreciation or volatility in cash flows for the period the item is being hedged. We view this strategy as a prudent management of interest rate risk. Please refer to Note 11, “Derivative Financial Instruments” in our 2017 Form 10-K for a full discussion of our risk management strategy. Title VII of the Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010 (the “Dodd-Frank Act”) requires all standardized derivatives, including most interest rate swaps, to be submitted for clearing to central counterparties to reduce counterparty risk. Two of the central counterparties we use are the Chicago Mercantile Exchange (“CME”) and the London Clearing House (“LCH”). The CME and the LCH made amendments to their respective rules that resulted in the prospective accounting treatment of certain daily variation margin payments being considered as the legal settlement of the outstanding exposure of the derivative instead of the posting of collateral. The CME rule changes, which became effective in January 2017, and the LCH rule changes, which became effective in January 2018, result in all variation margin payments on derivatives cleared through the CME and LCH being accounted for as legal settlement. As of September 30, 2018 , $6.6 billion notional of our derivative contracts were cleared on the CME and $0.6 billion were cleared on the LCH. The derivative contracts cleared through the CME and LCH represent 91.6 percent and 8.4 percent , respectively, of our total notional derivative contracts of $7.2 billion at September 30, 2018 . For derivatives cleared through the CME and LCH, the net gain (loss) position includes the variation margin amounts as settlement of the derivative and not collateral against the fair value of the derivative. Interest income (expense) related to variation margin on derivatives that are not designated as hedging instruments or are designated as fair value relationships is recognized as a gain (loss) rather than as interest income (expense). Changes in fair value for derivatives not designated as hedging instruments will be presented as realized gains (losses). Our exposure is limited to the value of the derivative contracts in a gain position less any collateral held and plus any collateral posted. When there is a net negative exposure, we consider our exposure to the counterparty to be zero. At September 30, 2018 and December 31, 2017, we had a net positive exposure (derivative gain positions to us, less collateral held by us and plus collateral posted with counterparties) related to derivatives of $33 million and $20 million, respectively. Summary of Derivative Financial Statement Impact The following tables summarize the fair values and notional amounts of all derivative instruments at September 30, 2018 and December 31, 2017 , and their impact on earnings and other comprehensive income for the three and nine months ended September 30, 2018 and 2017. Please refer to Note 11, “Derivative Financial Instruments” in our 2017 Form 10-K for a full discussion of cash flow hedges, fair value hedges, and trading activities. Impact of Derivatives on the Consolidated Balance Sheet Cash Flow Hedges Fair Value Hedges Trading Total September 30, December 31, September 30, December September 30, December September 30, December 2018 2017 2018 2017 2018 2017 2018 2017 Fair Values (1) Hedged Risk Exposure Derivative Assets: (2) Interest rate swaps Interest rate $ — $ — $ 1,306 $ 630 $ 78 $ 182 $ 1,384 $ 812 Derivative Liabilities: (2) Interest rate swaps Interest rate (454 ) (2,584 ) — — — — (454 ) (2,584 ) Total net derivatives $ (454 ) $ (2,584 ) $ 1,306 $ 630 $ 78 $ 182 $ 930 $ (1,772 ) ___________ (1) Fair values reported include variation margin as legal settlement of the derivative contract and accrued interest. Assets and liabilities are presented without consideration of master netting agreements. Derivatives are carried on the balance sheet based on net position by counterparty under master netting agreements and classified in other assets or other liabilities depending on whether in a net positive or negative position. (2) The following table reconciles gross positions with the impact of master netting agreements to the balance sheet classification: Other Assets Other Liabilities September 30, December 31, September 30, December 31, 2018 2017 2018 2017 Gross position (1) $ 1,384 $ 812 $ (454 ) $ (2,584 ) Impact of master netting agreement (340 ) (812 ) 340 812 Derivative values with impact of master netting agreements (as carried on balance sheet) 1,044 — (114 ) (1,772 ) Cash collateral pledged (2) 32,071 — — 21,586 Net position $ 33,115 $ — $ (114 ) $ 19,814 __________ (1) Gross position amounts include accrued interest and variation margin as legal settlement of the derivative contract. (2) Cash collateral pledged excludes amounts that represent legal settlement of the derivative contracts. Cash Flow Fair Value Trading Total September 30, December 31, September 30, December 31, September 30, December 31, September 30, December 31, 2018 2017 2018 2017 2018 2017 2018 2017 Notional Values Interest rate swaps $ 1,312,573 $ 1,408,649 $ 4,310,694 $ 3,062,849 $ 1,577,978 $ 987,577 $ 7,201,245 $ 5,459,075 As of September 30, 2018, and December 31, 2017, the following amounts were recorded on the consolidated balance sheet related to cumulative basis adjustments for fair value hedges: Line Item in the Balance Sheet in Which the Hedged Item is Included: Carrying Amount of the Hedged Assets/(Liabilities) Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Assets/(Liabilities) September 30, December 31, September 30, December 31, 2018 2017 2018 2017 Deposits $ (4,251,414 ) $ (3,036,671 ) $ 49,694 $ 22,168 Impact of Derivatives on the Consolidated Statements of Income Three Months Ended Nine Months Ended 2018 2017 2018 2017 Fair Value Hedges Interest rate swaps: Hedged items recorded in interest expense $ 4,809 $ 3,294 $ 27,526 $ 2,673 Derivatives recorded in interest expense (4,896 ) (546 ) (27,774 ) (7,803 ) Total $ (87 ) $ 2,748 $ (248 ) $ (5,130 ) Cash Flow Hedges Interest rate swaps: Amount of gain (loss) reclassified from accumulated other comprehensive income into interest expense $ (21 ) $ (2,689 ) $ (2,142 ) $ (8,697 ) Total $ (21 ) $ (2,689 ) $ (2,142 ) $ (8,697 ) Trading Interest rate swaps: Change in fair value of future interest payments recorded in earnings $ (1,557 ) $ (247 ) $ (8,492 ) $ (1,189 ) Total (1,557 ) (247 ) (8,492 ) (1,189 ) Total $ (1,665 ) $ (188 ) $ (10,882 ) $ (15,016 ) Impact of Derivatives on the Statements of Changes in Stockholders’ Equity Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Amount of gain recognized in other comprehensive income (loss) $ 6,453 $ 2,125 $ 34,718 $ (1,133 ) Less: amount of loss reclassified in interest expense (21 ) (2,689 ) (2,142 ) (8,697 ) Total change in other comprehensive income (loss) for unrealized gains (losses) on derivatives, before income tax (expense) benefit $ 6,474 $ 4,814 $ 36,860 $ 7,564 Cash Collateral As of September 30, 2018 , cash collateral held and pledged excludes amounts that represent legal settlement of the derivative contracts held with CME and LCH. Cash collateral held related to derivative exposure between us and our derivatives counterparties was zero at both September 30, 2018 and December 31, 2017 . Collateral held is recorded in “Other Liabilities” on the consolidated balance sheets. Cash collateral pledged related to derivative exposure between us and our derivatives counterparties was $32 million and $22 million at September 30, 2018 and December 31, 2017

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Common Stock The following table summarizes our common share repurchases and issuances. Three Months Ended Nine Months Ended (Shares and per share amounts in actuals) 2018 2017 2018 2017 Shares repurchased related to employee stock-based compensation plans (1)(2) 116,151 81,817 3,056,746 2,666,781 Average purchase price per share $ 11.54 $ 10.93 $ 11.34 $ 12.09 Common shares issued (3) 397,004 423,112 6,341,950 5,652,886 __________________ (1) Comprised of shares withheld from stock option exercises and vesting of restricted stock for employees’ tax withholding obligations and shares tendered by employees to satisfy option exercise costs. (2) At the present time, we do not intend to initiate a publicly announced share repurchase program. (3) Common shares issued under our various compensation and benefit plans. The closing price of our common stock on September 28, 2018 was $11.15

Earnings per Common Share

Earnings per Common Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Earnings per Common Share	Earnings per Common Share Basic earnings per common share (“EPS”) are calculated using the weighted average number of shares of common stock outstanding during each period. A reconciliation of the numerators and denominators of the basic and diluted EPS calculations follows. Three Months Ended Nine Months Ended September 30, September 30, (In thousands, except per share data) 2018 2017 2018 2017 Numerator: Net income $ 103,878 $ 76,371 $ 339,964 $ 241,931 Preferred stock dividends 4,124 3,028 11,441 12,577 Net income attributable to SLM Corporation common stock $ 99,754 $ 73,343 $ 328,523 $ 229,354 Denominator: Weighted average shares used to compute basic EPS 435,468 431,718 434,875 430,958 Effect of dilutive securities: Dilutive effect of stock options, restricted stock, restricted stock units and Employee Stock Purchase Plan (“ESPP”) (1)(2) 4,551 6,701 4,609 7,464 Weighted average shares used to compute diluted EPS 440,019 438,419 439,484 438,422 Basic earnings per common share attributable to SLM Corporation $ 0.23 $ 0.17 $ 0.76 $ 0.53 Diluted earnings per common share attributable to SLM Corporation $ 0.23 $ 0.17 $ 0.75 $ 0.52 ________________ (1) Includes the potential dilutive effect of additional common shares that are issuable upon exercise of outstanding stock options, restricted stock, restricted stock units, and the outstanding commitment to issue shares under the ESPP, determined by the treasury stock method. (2) For the three months ended September 30, 2018 and 2017, securities covering approximately 0 and 0 shares, respectively, and for the nine months ended September 30, 2018 and 2017, securities covering approximately 0 and 0

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements We use estimates of fair value in applying various accounting standards for our financial statements. We categorize our fair value estimates based on a hierarchical framework associated with three levels of price transparency utilized in measuring financial instruments at fair value. For additional information regarding our policies for determining fair value and the hierarchical framework, see Note 2, “Significant Accounting Policies - Fair Value Measurement” in our 2017 Form 10-K. During the nine months ended September 30, 2018 , there were no significant transfers of financial instruments between levels or changes in our methodology or assumptions used to value our financial instruments. The following table summarizes the valuation of our financial instruments that are marked to fair value on a recurring basis. Fair Value Measurements on a Recurring Basis September 30, 2018 December 31, 2017 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Available-for-sale investments $ — $ 172,370 $ — $ 172,370 $ — $ 244,088 $ — $ 244,088 Derivative instruments — 1,384 — 1,384 — 812 — 812 Total $ — $ 173,754 $ — $ 173,754 $ — $ 244,900 $ — $ 244,900 Liabilities Derivative instruments $ — $ (454 ) $ — $ (454 ) $ — $ (2,584 ) $ — $ (2,584 ) Total $ — $ (454 ) $ — $ (454 ) $ — $ (2,584 ) $ — $ (2,584 ) The following table summarizes the fair values of our financial assets and liabilities, including derivative financial instruments. September 30, 2018 December 31, 2017 Fair Value Carrying Value Difference Fair Value Carrying Value Difference Earning assets Loans held for investment, net $ 24,167,452 $ 21,978,903 $ 2,188,549 $ 20,673,136 $ 18,567,641 $ 2,105,495 Cash and cash equivalents 1,839,054 1,839,054 — 1,534,339 1,534,339 — Available-for-sale investments 172,370 172,370 — 244,088 244,088 — Accrued interest receivable 1,270,026 1,270,026 — 967,482 967,482 — Tax indemnification receivable 54,941 54,941 — 168,011 168,011 — Derivative instruments 1,384 1,384 — 812 812 — Total earning assets $ 27,505,227 $ 25,316,678 $ 2,188,549 $ 23,587,868 $ 21,482,373 $ 2,105,495 Interest-bearing liabilities Money-market and savings accounts $ 8,923,893 $ 8,923,893 $ — $ 8,470,209 $ 8,470,209 $ — Certificates of deposit 8,928,356 8,948,888 20,532 7,044,208 7,034,121 (10,087 ) Long-term borrowings 4,503,254 4,532,221 28,967 3,299,871 3,275,270 (24,601 ) Accrued interest payable 62,627 62,627 — 35,363 35,363 — Derivative instruments 454 454 — 2,584 2,584 — Total interest-bearing liabilities $ 22,418,584 $ 22,468,083 $ 49,499 $ 18,852,235 $ 18,817,547 $ (34,688 ) Excess of net asset fair value over carrying value $ 2,238,048 $ 2,070,807

Arrangements with Navient Corpo

Arrangements with Navient Corporation	9 Months Ended
	Sep. 30, 2018
Related Party Transactions [Abstract]
Arrangements with Navient Corporation	Arrangements with Navient Corporation In connection with the Spin-Off, we entered into a separation and distribution agreement (the “Separation and Distribution Agreement”) and other ancillary agreements with Navient. Please refer to Note 16, “Arrangements with Navient Corporation” in our 2017 Form 10-K for a full discussion of these agreements. Indemnification Obligations Navient is responsible for, and has agreed to indemnify us against, all claims, actions, damages, losses or expenses that may arise from the conduct of all activities of pre-Spin-Off SLM Corporation (“pre-Spin-Off SLM”) occurring prior to the Spin-Off other than those specifically excluded in the Separation and Distribution Agreement. Some significant examples of the types of indemnification obligations Navient has under the Separation and Distribution Agreement and related ancillary agreements include: • Navient will indemnify the Company and Sallie Mae Bank, a Utah industrial bank subsidiary of the Company (the “Bank”), for any liabilities, costs or expenses they may incur arising from any action or threatened action related to the servicing, operations and collections activities of pre-Spin-Off SLM and its subsidiaries with respect to Private Education Loans and FFELP Loans that were assets of the Bank or Navient at the time of the Spin-Off; provided that written notice was provided to Navient on or prior to April 30, 2017, the third anniversary date of the Spin-Off. Navient will not indemnify for changes in law or changes in prior existing interpretations of law that occur on or after April 30, 2014. • Pursuant to a tax sharing agreement, Navient has agreed to indemnify us for $283 million in deferred taxes that we are legally responsible for but that relate to gains recognized by our predecessor on debt repurchases made prior to the Spin-Off. The remaining amount of this indemnification at September 30, 2018 was $9 million . In connection with the Spin-Off, we also recorded a liability related to uncertain tax positions of $27 million for which we are indemnified by Navient. As of September 30, 2018, the remaining balance of the indemnification receivable related to those uncertain tax positions was $26 million . In the third-quarter 2016, we recognized a $120 million adjustment for tax positions relating to historical transactions among entities that are now subsidiaries of Navient that should have been recorded at the time of the Spin-Off, and a matching $120 million increase in our tax indemnification receivable from Navient, as we believe we are indemnified by Navient for those uncertain tax positions. In the third-quarter 2018, the federal statute of limitations expired with respect to $90 million of those amounts recorded in the third-quarter 2016 and, as such, we recorded an income tax benefit of $90 million and reduced the matching indemnification receivable by $90 million . At September 30, 2018, the remaining balances of the uncertain tax positions and the matching indemnification receivable recorded in the third-quarter 2016 were $20 million . Amended Loan Participation and Purchase Agreement Prior to the Spin-Off, the Bank sold substantially all of its Private Education Loans to several former affiliates, now subsidiaries of Navient (collectively, the “Purchasers”), pursuant to an Amended Loan Participation and Purchase Agreement. The agreement predates the Spin-Off but was significantly amended and reduced in scope in connection with the Spin-Off. Post-Spin-Off, the Bank retained only the right to require the Purchasers to purchase Split Loans (at fair value) when the Split Loans either (1) are more than 90 days past due; (2) have been restructured; (3) have been granted a hardship forbearance or more than six months of administrative forbearance; or (4) have a borrower or cosigner who has filed for bankruptcy. In the second quarter of 2018, we sold our remaining $43 million portfolio of Split Loans (both current and non-current loans) to Navient and recognized a net gain of $2 million

Regulatory Capital

Regulatory Capital	9 Months Ended
	Sep. 30, 2018
Banking and Thrift [Abstract]
Regulatory Capital	Regulatory Capital The Bank is subject to various regulatory capital requirements administered by the FDIC and the Utah Department of Financial Institutions (the “UDFI”). Failure to meet minimum capital requirements can initiate certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material adverse effect on our business, results of operation and financial condition. Under the FDIC’s regulations implementing the Basel III capital framework (“U.S. Basel III”) and the regulatory framework for prompt corrective action, the Bank must meet specific capital standards that involve quantitative measures of its assets, liabilities and certain off-balance sheet items as calculated under regulatory accounting practices. The Bank’s capital amounts and its classification under the prompt corrective action framework are also subject to qualitative judgments by the regulators about components of capital, risk weightings and other factors. The Bank is required to report regulatory capital and ratios in accordance with U.S. Basel III. Among other things, U.S. Basel III established Common Equity Tier 1 as a tier of capital, modified methods for calculating risk-weighted assets, introduced a capital conservation buffer (which is being phased in over several years), and revised the capital thresholds of the prompt corrective action framework, including the “well capitalized” standard. “Well capitalized” regulatory requirements are the quantitative measures established by regulation to ensure capital adequacy. To qualify as “well capitalized,” the Bank must maintain minimum amounts and ratios (set forth in the table below) of Common Equity Tier 1, Tier 1 and Total capital to risk-weighted assets and of Tier 1 capital to average assets. The following capital amounts and ratios are based upon the Bank’s assets. Actual “Well Capitalized” Amount Ratio Amount Ratio As of September 30, 2018: Common Equity Tier 1 Capital (to Risk-Weighted Assets) $ 2,735,622 11.5 % $ 1,541,678 > 6.5 % Tier 1 Capital (to Risk-Weighted Assets) $ 2,735,622 11.5 % $ 1,897,450 > 8.0 % Total Capital (to Risk-Weighted Assets) $ 3,032,522 12.8 % $ 2,371,812 > 10.0 % Tier 1 Capital (to Average Assets) $ 2,735,622 11.1 % $ 1,233,163 > 5.0 % As of December 31, 2017: Common Equity Tier 1 Capital (to Risk-Weighted Assets) $ 2,350,081 11.9 % $ 1,288,435 > 6.5 % Tier 1 Capital (to Risk-Weighted Assets) $ 2,350,081 11.9 % $ 1,585,767 > 8.0 % Total Capital (to Risk-Weighted Assets) $ 2,597,926 13.1 % $ 1,982,208 > 10.0 % Tier 1 Capital (to Average Assets) $ 2,350,081 11.0 % $ 1,067,739 > 5.0 % Bank Dividends The Bank is chartered under the laws of the State of Utah and its deposits are insured by the FDIC. The Bank’s ability to pay dividends is subject to the laws of Utah and the regulations of the FDIC. Generally, under Utah’s industrial bank laws and regulations as well as FDIC regulations, the Bank may pay dividends from its net profits without regulatory approval if, following the payment of the dividend, the Bank’s capital and surplus would not be impaired. The Bank paid no dividends for the nine months ended September 30, 2018 and September 30, 2017

Commitments, Contingencies and

Commitments, Contingencies and Guarantees	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments, Contingencies and Guarantees	Commitments, Contingencies and Guarantees Commitments When we approve a Private Education Loan at the beginning of an academic year, that approval may cover the borrowing for the entire academic year. As such, we do not always disburse the full amount of the loan at the time of such approval, but instead have a commitment to fund a portion of the loan at a later date (usually at the start of the second semester or subsequent trimesters). At September 30, 2018 , we had $ 2.1 billion of outstanding contractual loan commitments which we expect to fund during the remainder of the 2018/2019 academic year. At September 30, 2018 , we had a $ 2 million reserve recorded in “Other Liabilities” to cover expected losses that may occur during the one -year loss emergence period on these unfunded commitments. Regulatory Matters On May 13, 2014, the Bank reached a settlement with the Department of Justice ( the “DOJ”) regarding compliance with the Servicemembers Civil Relief Act (the “SCRA”). In connection with the settlement, the Bank became subject to a DOJ Consent Order, which was approved by the U.S. District Court for the District of Delaware on September 29, 2014 (the “DOJ Consent Order”). Under the terms of the Separation and Distribution Agreement executed in connection with the Spin-Off, Navient is responsible for funding all liabilities under the regulatory order and, as of the date hereof, has funded all liabilities other than fines directly levied against the Bank in connection with these matters which the Bank is required to pay. The DOJ Consent Order expired by its terms on September 29, 2018, and the related case was dismissed with prejudice on October 4, 2018. In May 2014, the Bank received a Civil Investigative Demand (“CID”) from the Consumer Financial Protection Bureau (the “CFPB”) as part of the CFPB’s separate investigation relating to customer complaints, fees and charges assessed in connection with the servicing of student loans and related collection practices of pre-Spin-Off SLM by entities now subsidiaries of Navient during a time period prior to the Spin-Off (the “CFPB Investigation”). Two state attorneys general also provided the Bank identical CIDs and other state attorneys general have become involved in the inquiry over time (collectively, the “Multi-State Investigation”). To the extent requested, the Bank has been cooperating fully with the CFPB and the attorneys general conducting the Multi-State Investigation. Given the timeframe covered by the CIDs, the CFPB Investigation, and the Multi-State Investigation, and the focus on practices and procedures previously conducted by Navient and its servicing subsidiaries prior to the Spin-Off, Navient is leading the response to these investigations. Consequently, we have no basis from which to estimate either the duration or ultimate outcome of these investigations. Additional lawsuits may arise from the Multi-State Investigation which may or may not name the Company, the Bank, or any of their current subsidiaries as parties to these suits. As with the Illinois and Mississippi lawsuits described below, the Bank is not responsible for any of the alleged conduct in the Multi-State Investigation or any claims that may arise from related lawsuits. As contemplated by the Separation and Distribution Agreement relating to, and the structure of, the Spin-Off, Navient is legally responsible for, has assumed, and has accepted responsibility to indemnify the Company against, all costs, expenses, losses and remediation that may arise from these matters. With regard to the CFPB Investigation, we note that on January 18, 2017, the CFPB filed a complaint in federal court in Pennsylvania against Navient, along with its subsidiaries, Navient Solutions, Inc. and Pioneer Credit Recovery, Inc. The complaint alleges these Navient entities, among other things, engaged in deceptive practices with respect to their historic servicing and debt collection practices. Neither SLM, the Bank, nor any of their current subsidiaries are named in, or otherwise a party to, the lawsuit and are not alleged to have engaged in any wrongdoing. The CFPB’s complaint asserts Navient’s assumption of these liabilities pursuant to the Separation and Distribution Agreement. On January 18, 2017, the Illinois Attorney General filed a lawsuit in Illinois state court against Navient - its subsidiaries Navient Solutions, Inc., Pioneer Credit Recovery, Inc., and General Revenue Corporation - and the Bank arising out of the Multi-State Investigation. On March 20, 2017, the Bank moved to dismiss the Illinois Attorney General action as to the Bank, arguing, among other things, the complaint failed to allege with sufficient particularity or specificity how the Bank was responsible for any of the alleged conduct, most of which predated the Bank’s existence. The Illinois Court heard oral arguments on July 18, 2017. On July 10, 2018, the Court granted the Bank’s motion to dismiss without prejudice. On August 7, 2018, the Illinois Attorney General filed a First Amended Complaint and, on October 9, 2018, the Bank again moved to dismiss the action based on grounds similar to those raised in its March 20, 2017 motion. Briefing on the Bank’s motion is expected to be complete on December 10, 2018, and oral argument is scheduled for January 9, 2019. On July 17, 2018, the Mississippi Attorney General filed a lawsuit in Mississippi state court against Navient, Navient Solutions, LLC, and the Bank arising out of the Multi-State Investigation. The complaint alleges unfair and deceptive trade practices against all three defendants as to private loan origination practices from 2000 to 2009. The complaint further alleges that Navient assumed responsibility for these matters under the Separation and Distribution Agreement for the alleged conduct. On October 8, 2018, the Bank moved to dismiss the Mississippi Attorney General’s action as to the Bank, arguing, among other things, that the complaint failed to allege with sufficient particularity or specificity how the Bank was responsible for any of the alleged conduct, most of which predated the Bank’s existence. To date, three other state attorneys general (California, Washington and Pennsylvania) have filed suits against Navient and one or more of its current subsidiaries arising out of the Multi-State Investigation. Neither SLM, the Bank, nor any of their current subsidiaries are named in, or otherwise a party to, the California, Washington or Pennsylvania lawsuits, and no claims are asserted against them. Each complaint asserts in its own fashion that Navient assumed responsibility under the Separation and Distribution Agreement for the alleged conduct in the complaints. On September 24, 2018, the Washington Attorney General served a third-party subpoena on the Bank calling for the production of certain records. The Bank is preparing its response to the subpoena. As contemplated by the Separation and Distribution Agreement relating to, and the structure of, the Spin-Off, Navient is legally responsible for all costs, expenses, losses and remediation that may arise from the lawsuits filed by the Illinois and Mississippi Attorneys General and the Bank’s response to the Washington Attorney General’s subpoena. Navient has accepted responsibility to indemnify the Company in these matters pursuant to the Separation and Distribution Agreement. Contingencies In the ordinary course of business, we and our subsidiaries are routinely defendants in or parties to pending and threatened legal actions and proceedings, including actions brought on behalf of various classes of claimants. These actions and proceedings may be based on alleged violations of consumer protection, securities, employment and other laws. In certain of these actions and proceedings, claims for substantial monetary damages may be asserted against us and our subsidiaries. It is common for the Company, our subsidiaries and affiliates to receive information and document requests and investigative demands from state attorneys general, legislative committees, and administrative agencies. These requests may be for informational or regulatory purposes and may relate to our business practices, the industries in which we operate, or other companies with whom we conduct business. Our practice has been and continues to be to cooperate with these bodies and be responsive to any such requests. We are required to establish reserves for litigation and regulatory matters where those matters present loss contingencies that are both probable and estimable. When loss contingencies are not both probable and estimable, we do not establish reserves.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited, consolidated financial statements of SLM Corporation (“Sallie Mae,” “SLM,” the “Company,” “we,” or “us”) have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) for interim financial information. Accordingly, they do not include all the information and footnotes required by GAAP for complete consolidated financial statements. The consolidated financial statements include the accounts of SLM Corporation and its majority-owned and controlled subsidiaries after eliminating the effects of intercompany accounts and transactions. In the opinion of management, all adjustments considered necessary for a fair statement of the results for the interim periods have been included. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. Operating results for the three and nine months ended September 30, 2018 are not necessarily indicative of the results for the year ending December 31, 2018 or for any other period. These unaudited financial statements should be read in conjunction with the audited financial statements and related notes included in our Annual Report on Form 10-K for the year ended December 31, 2017 (the “2017 Form 10-K”).
Consolidation	Consolidation The consolidated financial statements include the accounts of the Company and its majority-owned and controlled subsidiaries after eliminating the effects of intercompany accounts and transactions.
Recently Issued and Adopted Accounting Pronouncements	Recently Issued and Adopted Accounting Pronouncements ASU No. 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash” In November 2016, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update (“ASU”) No. 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash.” Whereas restricted cash balances have traditionally been excluded from the statement of cash flows, this ASU requires restricted cash and restricted cash equivalents to be included within the beginning and ending totals of cash, cash equivalents and restricted cash presented on the statement of cash flows for all periods presented. Restricted cash and restricted cash equivalent inflows and outflows with external parties are required to be classified within the operating, investing, and/or financing activity sections of the statement of cash flows, whereas transfers between cash and cash equivalents and restricted cash and restricted cash equivalents should no longer be presented on the statement of cash flows. ASU No. 2016-18 also requires (a) the nature of the restrictions to be disclosed to help provide information about the sources and uses of these balances during a reporting period and (b) a reconciliation of the cash, cash equivalents and restricted cash totals on the statement of cash flows to the related balance sheet line items when cash, cash equivalents, and restricted cash are presented in more than one line item on the balance sheet. The reconciliation can be presented either on the face of the statement of cash flows or in the notes to the financial statements and must be provided for each period that a balance sheet is presented. We adopted the new accounting pronouncement on January 1, 2018, and the adoption did not have a material impact to our statement of cash flows. ASU No. 2017-12, “Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities” On August 28, 2017, the FASB issued ASU No. 2017-12, “Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities,” which (a) improves the financial reporting of hedging relationships to better portray the economic results of an entity's risk management activities in its financial statements and (b) makes certain targeted improvements to simplify the application of the hedge accounting guidance. The effective date for the standard is January 1, 2019, with early adoption permitted. We elected to early adopt the standard effective July 1, 2018. One of the key changes is that the standard eliminates the separate measurement and reporting of hedge ineffectiveness. In accordance with the new standard, certain provisions were required to be applied on a modified retrospective basis, which requires a cumulative effect adjustment to accumulated other comprehensive income with a corresponding adjustment to retained earnings as of the beginning of the fiscal year of adoption, or January 1, 2018 in our case. The accounting for derivative instruments requires that every derivative instrument, including certain derivative instruments embedded in other contracts, be recorded on the balance sheet as either an asset or liability measured at fair value. Our derivative instruments are classified and accounted for by us as fair value hedges, cash flow hedges, or trading hedges. Fair Value Hedges We generally use fair value hedges to offset the exposure to changes in fair value of a recognized fixed-rate liability. We enter into interest rate swaps to economically convert fixed-rate liabilities into variable-rate liabilities. For fair value hedges, we generally consider all components of the derivative’s gain and/or loss when assessing hedge effectiveness and generally hedge changes in fair values due to interest rates. Under the new standard, for fair value hedges, the entire change in the fair value of the hedging instrument included in the assessment of hedge effectiveness is recorded in the same line item in the consolidated statements of income that is used to present the earnings effect of the hedged component of the hedged item. The timing of recognition of the change in fair value of a hedging instrument included in the assessment of hedge effectiveness is the same as prior to the adoption of ASU No. 2017-12. Cash Flow Hedges We use cash flow hedges to hedge the exposure to variability in cash flows of floating-rate liabilities. This strategy is used primarily to minimize the exposure to volatility in cash flows from future changes in interest rates. In assessing hedge effectiveness, generally all components of each derivative’s gains or losses are included in the assessment. We hedge exposure to changes in cash flows due to changes in interest rates or total changes in cash flow. Under the new standard, for cash flow hedges, the entire change in the fair value of the hedging instrument included in the assessment of hedge effectiveness is recorded in other comprehensive income (loss). Those amounts are subsequently reclassified to earnings, in the same line item in the consolidated statements of income as impacted by the hedged item, when the hedged item affects earnings. Amounts reported in accumulated other comprehensive income related to derivatives will be reclassified to interest expense as interest payments are made on our variable-rate deposits. During the next twelve months, we estimate that $7 million will be reclassified as an increase to interest expense. Trading Activities When derivative instruments do not qualify for hedge accounting treatment, they are accounted for at fair value with all changes in fair value recorded through earnings. All of our derivative instruments with maturities of less than 3 years are economically hedging risk, but do not receive hedge accounting treatment. Trading derivatives also include any hedges that originally received hedge accounting treatment, but lost hedge accounting treatment due to failed effectiveness testing, as well as the activity of certain derivatives prior to those derivatives receiving hedge accounting treatment. Cumulative effect of applying the new standard As a result of the cumulative effect of applying the new hedging standard to our fair value hedges on July 1, 2018, we recorded a $2.0 million basis increase to our hedged deposit balances with a corresponding increase to retained earnings of approximately $1.0 million and a $3.0 million loss to “gains (losses) on derivatives and hedging activities, net” in our consolidated statements of income to adjust the life-to-date ineffectiveness. To reflect the adoption of the new hedging standard on our cash flow hedging relationships at July 1, 2018, we recorded a $0.3 million decrease to retained earnings and a corresponding $0.3 million increase to accumulated other comprehensive income. The new standard also requires modifications to existing presentation and disclosure requirements. We did not apply adjustments to our prior period consolidated balance sheets or consolidated statements of income as a result of adopting the new hedging standard. However, certain disclosures within the notes to the financial statements set forth in this report, regarding the three and nine month periods ended September 30, 2017, conform to the disclosure requirements of ASU No. 2017-12. For further details, refer to Note 7, “Derivative Financial Instruments.” ASU No. 2018-02, “Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income” In February 2018, the FASB issued ASU No. 2018-02, “Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income,” which allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the tax law and tax rate changes under the Tax Cuts and Jobs Act of 2017 (the “Tax Act”) enacted on December 22, 2017. Under the Tax Act, deferred taxes were adjusted to reflect the reduction of the historical corporate income tax rate to the newly enacted corporate income tax rate, which left the tax effects on items within accumulated other comprehensive income stranded at an inappropriate tax rate. This guidance is effective for fiscal years beginning after December 15, 2018, and for interim periods within those fiscal years, with early adoption permitted. We adopted this standard effective January 1, 2018 and recorded a $0.6 million

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Schedule of amortized cost and fair value of securities available for sale	The amortized cost and fair value of securities available for sale are as follows: September 30, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Available for sale: Mortgage-backed securities $ 159,397 $ 92 $ (8,046 ) $ 151,443 Utah Housing Corporation bonds 22,388 — (1,461 ) 20,927 Total $ 181,785 $ 92 $ (9,507 ) $ 172,370 December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Available for sale: Mortgage-backed securities $ 227,607 $ 650 $ (3,210 ) $ 225,047 Utah Housing Corporation bonds 20,000 — (959 ) 19,041 Total $ 247,607 $ 650 $ (4,169 ) $ 244,088
Available-for-sale securities, continuous unrealized loss position, fair value	The following table summarizes the amount of gross unrealized losses for our mortgage-backed securities and Utah Housing Corporation bonds and the estimated fair value for securities having gross unrealized losses, categorized by length of time the securities have been in an unrealized loss position: Less than 12 months 12 months or more Total Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value Gross Unrealized Losses Estimated Fair Value As of September 30, 2018: Mortgage-backed securities $ (1,768 ) $ 43,253 $ (6,278 ) $ 104,841 $ (8,046 ) $ 148,094 Utah Housing Corporation bonds (125 ) 4,875 (1,336 ) 16,052 (1,461 ) 20,927 Total $ (1,893 ) $ 48,128 $ (7,614 ) $ 120,893 $ (9,507 ) $ 169,021 As of December 31, 2017: Mortgage-backed securities $ (772 ) $ 77,356 $ (2,438 ) $ 110,500 $ (3,210 ) $ 187,856 Utah Housing Corporation bonds (77 ) 4,923 (882 ) 14,118 (959 ) 19,041 Total $ (849 ) $ 82,279 $ (3,320 ) $ 124,618 $ (4,169 ) $ 206,897
Schedule of amortized cost and fair value of securities, by contractual maturities	As of September 30, 2018, the amortized cost and fair value of securities, by contractual maturities, are summarized below. Contractual maturities versus actual maturities may differ due to the effect of prepayments. Year of Maturity Amortized Cost Estimated Fair Value 2038 $ 267 $ 281 2039 2,990 3,068 2042 9,524 8,766 2043 14,396 13,728 2044 23,437 22,535 2045 25,868 24,468 2046 40,006 37,703 2047 57,395 54,082 2048 7,902 7,739 Total $ 181,785 $ 172,370

Loans Held for Investment (Tabl

Loans Held for Investment (Tables)	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Schedule of Accounts, Notes, Loans and Financing Receivable	The average balance and the respective weighted average interest rates of loans in our portfolio are summarized as follows: Three Months Ended September 30, 2018 2017 Average Balance Weighted Average Interest Rate Average Balance Weighted Average Interest Rate Private Education Loans $ 19,295,318 9.16 % $ 16,228,751 8.50 % FFELP Loans 877,279 4.65 960,185 4.02 Personal Loans 1,082,177 11.03 86,441 9.66 Total portfolio $ 21,254,774 $ 17,275,377 Nine Months Ended September 30, 2018 2017 Average Balance Weighted Average Interest Rate Average Balance Weighted Average Interest Rate Private Education Loans $ 18,908,929 9.01 % $ 15,791,557 8.37 % FFELP Loans 898,208 4.47 981,106 3.86 Personal Loans 810,753 10.82 61,263 9.44 Total portfolio $ 20,617,890 $ 16,833,926 September 30, December 31, 2018 2017 Private Education Loans: Fixed rate $ 6,369,950 $ 4,000,447 Variable rate 13,870,041 13,431,720 Total Private Education Loans, gross 20,239,991 17,432,167 Deferred origination costs and unamortized premium/(discount) 65,499 56,378 Allowance for loan losses (274,684 ) (243,715 ) Total Private Education Loans, net 20,030,806 17,244,830 FFELP Loans 866,786 927,660 Deferred origination costs and unamortized premium/(discount) 2,432 2,631 Allowance for loan losses (1,080 ) (1,132 ) Total FFELP Loans, net 868,138 929,159 Personal Loans (fixed rate) 1,133,005 400,280 Deferred origination costs and unamortized premium/(discount) 164 — Allowance for loan losses (53,210 ) (6,628 ) Total Personal Loans, net 1,079,959 393,652 Loans held for investment, net $ 21,978,903 $ 18,567,641 Three Months Ended 2018 2017 Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized TDR Loans $ 1,180,206 $ 19,943 $ 877,011 $ 16,517 Nine Months Ended 2018 2017 Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized TDR Loans $ 1,106,946 $ 56,509 $ 772,362 $ 43,084

Allowance for Loan Losses (Tabl

Allowance for Loan Losses (Tables)	9 Months Ended
	Sep. 30, 2018
Receivables [Abstract]
Allowance for credit losses and recorded investments in loans	Allowance for Loan Losses Metrics Allowance for Loan Losses Three Months Ended September 30, 2018 FFELP Loans Private Education Loans Personal Loans Total Allowance for Loan Losses Beginning balance $ 1,073 $ 261,695 $ 32,509 $ 295,277 Total provision 259 42,482 26,155 68,896 Net charge-offs: Charge-offs (252 ) (34,229 ) (5,740 ) (40,221 ) Recoveries — 4,736 286 5,022 Net charge-offs (252 ) (29,493 ) (5,454 ) (35,199 ) Loan sales (1) — — — — Ending Balance $ 1,080 $ 274,684 $ 53,210 $ 328,974 Allowance: Ending balance: individually evaluated for impairment $ — $ 119,643 $ — $ 119,643 Ending balance: collectively evaluated for impairment $ 1,080 $ 155,041 $ 53,210 $ 209,331 Loans: Ending balance: individually evaluated for impairment $ — $ 1,199,493 $ — $ 1,199,493 Ending balance: collectively evaluated for impairment $ 866,786 $ 19,040,498 $ 1,133,005 $ 21,040,289 Net charge-offs as a percentage of average loans in repayment (annualized) (2) 0.15 % 0.88 % 2.03 % Allowance as a percentage of the ending total loan balance 0.12 % 1.36 % 4.70 % Allowance as a percentage of the ending loans in repayment (2) 0.16 % 1.99 % 4.70 % Allowance coverage of net charge-offs (annualized) 1.07 2.33 2.44 Ending total loans, gross $ 866,786 $ 20,239,991 $ 1,133,005 Average loans in repayment (2) $ 681,131 $ 13,351,517 $ 1,072,624 Ending loans in repayment (2) $ 679,110 $ 13,815,415 $ 1,133,005 ____________ (1) Represents fair value adjustments on loans sold. (2) Loans in repayment include loans on which borrowers are making interest only or fixed payments, as well as loans that have entered full principal and interest repayment status after any applicable grace period. Allowance for Loan Losses Three Months Ended September 30, 2017 FFELP Loans Private Education Loans Personal Loans Total Allowance for Loan Losses Beginning balance $ 1,606 $ 205,024 $ 818 $ 207,448 Total provision (73 ) 53,120 800 53,847 Net charge-offs: Charge-offs (181 ) (34,280 ) (220 ) (34,681 ) Recoveries — 4,560 2 4,562 Net charge-offs (181 ) (29,720 ) (218 ) (30,119 ) Loan sales (1) — (1,257 ) — (1,257 ) Ending Balance $ 1,352 $ 227,167 $ 1,400 $ 229,919 Allowance: Ending balance: individually evaluated for impairment $ — $ 100,999 $ — $ 100,999 Ending balance: collectively evaluated for impairment $ 1,352 $ 126,168 $ 1,400 $ 128,920 Loans: Ending balance: individually evaluated for impairment $ — $ 942,561 $ — $ 942,561 Ending balance: collectively evaluated for impairment $ 949,180 $ 16,190,346 $ 132,100 $ 17,271,626 Net charge-offs as a percentage of average loans in repayment (annualized) (2) 0.10 % 1.08 % 0.96 % Allowance as a percentage of the ending total loan balance 0.14 % 1.33 % 1.06 % Allowance as a percentage of the ending loans in repayment (2) 0.20 % 1.99 % 1.06 % Allowance coverage of net charge-offs (annualized) 1.87 1.91 1.60 Ending total loans, gross $ 949,180 $ 17,132,907 $ 132,100 Average loans in repayment (2) $ 734,613 $ 10,971,028 $ 90,850 Ending loans in repayment (2) $ 690,849 $ 11,406,581 $ 132,100 ____________ (1) Represents fair value adjustments on loans sold. (2) Loans in repayment include loans on which borrowers are making interest only or fixed payments, as well as loans that have entered full principal and interest repayment status after any applicable grace period. Allowance for Loan Losses Nine Months Ended September 30, 2018 FFELP Loans Private Education Loans Personal Loans Total Allowance for Loan Losses Beginning balance $ 1,132 $ 243,715 $ 6,628 $ 251,475 Total provision 742 130,616 55,981 187,339 Net charge-offs: Charge-offs (794 ) (113,852 ) (9,812 ) (124,458 ) Recoveries — 15,421 413 15,834 Net charge-offs (794 ) (98,431 ) (9,399 ) (108,624 ) Loan sales (1) — (1,216 ) — (1,216 ) Ending Balance $ 1,080 $ 274,684 $ 53,210 $ 328,974 Allowance: Ending balance: individually evaluated for impairment $ — $ 119,643 $ — $ 119,643 Ending balance: collectively evaluated for impairment $ 1,080 $ 155,041 $ 53,210 $ 209,331 Loans: Ending balance: individually evaluated for impairment $ — $ 1,199,493 $ — $ 1,199,493 Ending balance: collectively evaluated for impairment $ 866,786 $ 19,040,498 $ 1,133,005 $ 21,040,289 Net charge-offs as a percentage of average loans in repayment (annualized) (2) 0.15 % 1.01 % 1.56 % Allowance as a percentage of the ending total loan balance 0.12 % 1.36 % 4.70 % Allowance as a percentage of the ending loans in repayment (2) 0.16 % 1.99 % 4.70 % Allowance coverage of net charge-offs (annualized) 1.02 2.09 4.25 Ending total loans, gross $ 866,786 $ 20,239,991 $ 1,133,005 Average loans in repayment (2) $ 700,679 $ 13,009,704 $ 803,928 Ending loans in repayment (2) $ 679,110 $ 13,815,415 $ 1,133,005 ____________ (1) Represents fair value adjustments on loans sold. (2) Loans in repayment include loans on which borrowers are making interest only or fixed payments, as well as loans that have entered full principal and interest repayment status after any applicable grace period. Allowance for Loan Losses Nine Months Ended September 30, 2017 FFELP Loans Private Education Loans Personal Loans Total Allowance for Loan Losses Beginning balance $ 2,171 $ 182,472 $ 58 $ 184,701 Total provision (161 ) 129,105 1,580 130,524 Net charge-offs: Charge-offs (658 ) (93,235 ) (240 ) (94,133 ) Recoveries — 12,216 2 12,218 Net charge-offs (658 ) (81,019 ) (238 ) (81,915 ) Loan sales (1) — (3,391 ) — (3,391 ) Ending Balance $ 1,352 $ 227,167 $ 1,400 $ 229,919 Allowance: Ending balance: individually evaluated for impairment $ — $ 100,999 $ — $ 100,999 Ending balance: collectively evaluated for impairment $ 1,352 $ 126,168 $ 1,400 $ 128,920 Loans: Ending balance: individually evaluated for impairment $ — $ 942,561 $ — $ 942,561 Ending balance: collectively evaluated for impairment $ 949,180 $ 16,190,346 $ 132,100 $ 17,271,626 Net charge-offs as a percentage of average loans in repayment (annualized) (2) 0.12 % 1.02 % 0.51 % Allowance as a percentage of the ending total loan balance 0.14 % 1.33 % 1.06 % Allowance as a percentage of the ending loans in repayment (2) 0.20 % 1.99 % 1.06 % Allowance coverage of net charge-offs (annualized) 1.54 2.10 4.41 Ending total loans, gross $ 949,180 $ 17,132,907 $ 132,100 Average loans in repayment (2) $ 752,990 $ 10,589,725 $ 62,747 Ending loans in repayment (2) $ 690,849 $ 11,406,581 $ 132,100 ____________ (1) Represents fair value adjustments on loans sold. (2)
Impaired financing receivables	The following table provides the recorded investment, unpaid principal balance and related allowance for our TDR loans. Recorded Investment Unpaid Principal Balance Allowance September 30, 2018 TDR Loans $ 1,220,233 $ 1,199,493 $ 119,643 December 31, 2017 TDR Loans $ 1,007,141 $ 990,351 $ 94,682
Average recorded investment and interest income recognized for troubled debt restructuring loans	The average balance and the respective weighted average interest rates of loans in our portfolio are summarized as follows: Three Months Ended September 30, 2018 2017 Average Balance Weighted Average Interest Rate Average Balance Weighted Average Interest Rate Private Education Loans $ 19,295,318 9.16 % $ 16,228,751 8.50 % FFELP Loans 877,279 4.65 960,185 4.02 Personal Loans 1,082,177 11.03 86,441 9.66 Total portfolio $ 21,254,774 $ 17,275,377 Nine Months Ended September 30, 2018 2017 Average Balance Weighted Average Interest Rate Average Balance Weighted Average Interest Rate Private Education Loans $ 18,908,929 9.01 % $ 15,791,557 8.37 % FFELP Loans 898,208 4.47 981,106 3.86 Personal Loans 810,753 10.82 61,263 9.44 Total portfolio $ 20,617,890 $ 16,833,926 September 30, December 31, 2018 2017 Private Education Loans: Fixed rate $ 6,369,950 $ 4,000,447 Variable rate 13,870,041 13,431,720 Total Private Education Loans, gross 20,239,991 17,432,167 Deferred origination costs and unamortized premium/(discount) 65,499 56,378 Allowance for loan losses (274,684 ) (243,715 ) Total Private Education Loans, net 20,030,806 17,244,830 FFELP Loans 866,786 927,660 Deferred origination costs and unamortized premium/(discount) 2,432 2,631 Allowance for loan losses (1,080 ) (1,132 ) Total FFELP Loans, net 868,138 929,159 Personal Loans (fixed rate) 1,133,005 400,280 Deferred origination costs and unamortized premium/(discount) 164 — Allowance for loan losses (53,210 ) (6,628 ) Total Personal Loans, net 1,079,959 393,652 Loans held for investment, net $ 21,978,903 $ 18,567,641 Three Months Ended 2018 2017 Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized TDR Loans $ 1,180,206 $ 19,943 $ 877,011 $ 16,517 Nine Months Ended 2018 2017 Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized TDR Loans $ 1,106,946 $ 56,509 $ 772,362 $ 43,084
Age analysis of past due loans delinquencies	The following table provides information regarding the loan status of our Private Education Loans. Loans in repayment include loans making interest only or fixed payments, as well as loans that have entered full principal and interest repayment status after any applicable grace period. Private Education Loans September 30, December 31, 2018 2017 Balance % Balance % Loans in-school/grace/deferment (1) $ 5,936,033 $ 4,757,732 Loans in forbearance (2) 488,543 468,402 Loans in repayment and percentage of each status: Loans current 13,492,029 97.7 % 11,911,128 97.6 % Loans delinquent 31-60 days (3) 198,987 1.4 179,002 1.5 Loans delinquent 61-90 days (3) 82,358 0.6 78,292 0.6 Loans delinquent greater than 90 days (3) 42,041 0.3 37,611 0.3 Total Private Education Loans in repayment 13,815,415 100.0 % 12,206,033 100.0 % Total Private Education Loans, gross 20,239,991 17,432,167 Private Education Loans deferred origination costs and unamortized premium/(discount) 65,499 56,378 Total Private Education Loans 20,305,490 17,488,545 Private Education Loans allowance for losses (274,684 ) (243,715 ) Private Education Loans, net $ 20,030,806 $ 17,244,830 Percentage of Private Education Loans in repayment 68.3 % 70.0 % Delinquencies as a percentage of Private Education Loans in repayment 2.3 % 2.4 % Loans in forbearance as a percentage of Private Education Loans in repayment and forbearance 3.4 % 3.7 % (1) Deferment includes customers who have returned to school or are engaged in other permitted educational activities and are not yet required to make payments on the loans (e.g., residency periods for medical students or a grace period for bar exam preparation). (2) Loans for customers who have requested extension of grace period generally during employment transition or who have temporarily ceased making full payments due to hardship or other factors, consistent with established loan program servicing policies and procedures. (3) September 30, December 31, 2018 2017 Balance % Balance % TDR loans in in-school/grace/deferment (1) $ 68,848 $ 51,745 TDR loans in forbearance (2) 73,403 69,652 TDR loans in repayment (3) and percentage of each status: Loans current 954,309 90.3 % 774,222 89.1 % Loans delinquent 31-60 days (4) 51,979 4.9 48,377 5.6 Loans delinquent 61-90 days (4) 31,582 3.0 28,778 3.3 Loans delinquent greater than 90 days (4) 19,372 1.8 17,577 2.0 Total TDR loans in repayment 1,057,242 100.0 % 868,954 100.0 % Total TDR loans, gross $ 1,199,493 $ 990,351 _____ (1) Deferment includes customers who have returned to school or are engaged in other permitted educational activities and are not yet required to make payments on the loans (e.g., residency periods for medical students or a grace period for bar exam preparation). (2) Loans for customers who have requested extension of grace period generally during employment transition or who have temporarily ceased making full payments due to hardship or other factors, consistent with established loan program servicing policies and procedures. (3) Loans in repayment include loans on which borrowers are making interest only or fixed payments, as well as loans that have entered full principal and interest repayment status after any applicable grace period. (4)
Modified loans accounts for troubled debt restructuring	The following table provides the amount of modified loans (which include forbearance and reductions in interest rates) that became TDRs in the periods presented. Additionally, for the periods presented, the table summarizes charge-offs occurring in the TDR portfolio, as well as TDRs for which a payment default occurred in the relevant period presented and within 12 months of the loan first being designated as a TDR. We define payment default as more than 60 days past due for this disclosure. Three Months Ended Three Months Ended Modified Loans (1) Charge-offs Payment- Default Modified Loans (1) Charge-offs Payment- Default TDR Loans $ 101,117 $ 11,090 $ 20,595 $ 168,645 $ 12,227 $ 28,275 Nine Months Ended Nine Months Ended Modified Loans (1) Charge-offs Payment- Default Modified Loans (1) Charge-offs Payment- Default TDR Loans $ 301,769 $ 39,315 $ 68,430 $ 415,341 $ 34,965 $ 77,248 _____ (1)
Private education loan portfolio stratified by key credit quality indicators	The following table highlights the gross principal balance of our Private Education Loan portfolio stratified by key credit quality indicators. Private Education Loans Credit Quality Indicators September 30, 2018 December 31, 2017 Credit Quality Indicators: Balance (1) % of Balance Balance (1) % of Balance Cosigners: With cosigner $ 18,147,180 90 % $ 15,658,539 90 % Without cosigner 2,092,811 10 1,773,628 10 Total $ 20,239,991 100 % $ 17,432,167 100 % FICO at Original Approval (2) : Less than 670 $ 1,373,155 7 % $ 1,153,591 6 % 670-699 3,042,228 15 2,596,959 15 700-749 6,655,405 33 5,714,554 33 Greater than or equal to 750 9,169,203 45 7,967,063 46 Total $ 20,239,991 100 % $ 17,432,167 100 % Seasoning (3) : 1-12 payments $ 5,419,487 27 % $ 4,256,592 24 % 13-24 payments 3,238,910 16 3,229,465 19 25-36 payments 2,533,308 13 2,429,238 14 37-48 payments 1,638,309 8 1,502,327 9 More than 48 payments 1,473,944 7 1,256,813 7 Not yet in repayment 5,936,033 29 4,757,732 27 Total $ 20,239,991 100 % $ 17,432,167 100 % (1) Balance represents gross Private Education Loans. (2) Represents the higher credit score of the cosigner or the borrower. (3) Personal Loans September 30, December 31, 2018 2017 Balance % Balance % Loans in repayment and percentage of each status: Loans current $ 1,123,597 99.2 % $ 398,988 99.7 % Loans delinquent 31-60 days (1) 4,321 0.4 761 0.2 Loans delinquent 61-90 days (1) 2,804 0.2 340 0.1 Loans delinquent greater than 90 days (1) 2,283 0.2 191 — Total Personal Loans in repayment 1,133,005 100.0 % 400,280 100.0 % Total Personal Loans, gross 1,133,005 400,280 Personal Loans deferred origination costs and unamortized premium/(discount) 164 — Total Personal Loans 1,133,169 400,280 Personal Loans allowance for losses (53,210 ) (6,628 ) Personal Loans, net $ 1,079,959 $ 393,652 Delinquencies as a percentage of Personal Loans in repayment 0.8 % 0.3 % _______ (1) Personal Loans Credit Quality Indicators September 30, 2018 December 31, 2017 Credit Quality Indicators: Balance (1) % of Balance Balance (1) % of Balance FICO at Original Approval: Less than 670 $ 79,769 7 % $ 32,156 8 % 670-699 327,364 29 114,731 29 700-749 520,370 46 182,025 45 Greater than or equal to 750 205,502 18 71,368 18 Total $ 1,133,005 100 % $ 400,280 100 % Seasoning (2) : 0-12 payments $ 1,084,706 96 % $ 400,280 100 % 13-24 payments 48,299 4 — — 25-36 payments — — — — 37-48 payments — — — — More than 48 payments — — — — Total $ 1,133,005 100 % $ 400,280 100 % (1) Balance represents gross Personal Loans. (2)
Accrued interest receivable	The following table provides information regarding accrued interest receivable on our Private Education Loans. The table also discloses the amount of accrued interest on loans greater than 90 days past due as compared to our allowance for uncollectible interest. The allowance for uncollectible interest exceeds the amount of accrued interest on our 90 days past due Private Education Loan portfolio for all periods presented. Private Education Loans Accrued Interest Receivable Total Interest Receivable Greater Than 90 Days Past Due Allowance for Uncollectible Interest September 30, 2018 $ 1,250,288 $ 1,594 $ 6,462 December 31, 2017 $ 951,138 $ 1,372 $ 4,664

Deposits (Tables)

Deposits (Tables)	9 Months Ended
	Sep. 30, 2018
Banking and Thrift [Abstract]
Schedule of deposits	The following table summarizes total deposits at September 30, 2018 and December 31, 2017 . September 30, December 31, 2018 2017 Deposits - interest bearing $ 17,872,781 $ 15,504,330 Deposits - non-interest bearing 512 1,053 Total deposits $ 17,873,293 $ 15,505,383
Interest bearing deposits	Interest bearing deposits at September 30, 2018 and December 31, 2017 are summarized as follows: September 30, 2018 December 31, 2017 Amount Qtr.-End Weighted Average Stated Rate (1) Amount Year-End Weighted Average Stated Rate (1) Money market $ 8,239,595 2.29 % $ 7,731,966 1.80 % Savings 684,298 1.70 738,243 1.10 Certificates of deposit 8,948,888 2.65 7,034,121 1.93 Deposits - interest bearing $ 17,872,781 $ 15,504,330 ____________ (1)

Borrowings (Tables)

Borrowings (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Schedule of debt	The following table summarizes our borrowings at September 30, 2018 and December 31, 2017 . September 30, 2018 December 31, 2017 Short-Term Long-Term Total Short-Term Long-Term Total Unsecured borrowings: Unsecured debt $ — $ 197,146 $ 197,146 $ — $ 196,539 $ 196,539 Total unsecured borrowings — 197,146 197,146 — 196,539 196,539 Secured borrowings: Private Education Loan term securitizations: Fixed rate — 2,337,004 2,337,004 — 1,565,760 1,565,760 Variable rate — 1,998,071 1,998,071 — 1,512,971 1,512,971 Total Private Education Loan term securitizations — 4,335,075 4,335,075 — 3,078,731 3,078,731 ABCP Facility — — — — — — Total secured borrowings — 4,335,075 4,335,075 — 3,078,731 3,078,731 Total $ — $ 4,532,221 $ 4,532,221 $ — $ 3,275,270 $ 3,275,270
Schedule of securities financing transactions	Secured Financings at Issuance Issue Date Issued Total Issued Weighted Average Cost of Funds (1) Weighted Average Life (in years) Private Education: 2016-A May 2016 $ 501,000 1-month LIBOR plus 1.38% 4.01 2016-B July 2016 607,000 1-month LIBOR plus 1.36% 4.01 2016-C October 2016 674,000 1-month LIBOR plus 1.15% 4.27 Total notes issued in 2016 $ 1,782,000 Total loan and accrued interest amount securitized at inception in 2016 $ 2,107,042 2017-A February 2017 $ 772,000 1-month LIBOR plus 0.93% 4.27 2017-B November 2017 676,000 1-month LIBOR plus 0.80% 4.07 Total notes issued in 2017 $ 1,448,000 Total loan and accrued interest amount securitized at inception in 2017 $ 1,606,804 2018-A March 2018 $ 670,000 1-month LIBOR plus 0.78% 4.43 2018-B June 2018 686,500 1-month LIBOR plus 0.76% 4.40 2018-C September 2018 544,000 1-month LIBOR plus 0.77% 4.32 Total notes issued in 2018 $ 1,900,500 Total loan and accrued interest amount securitized at inception in 2018 $ 2,101,644 ____________ (1)
Schedule of variable interest entities	We consolidate the following financing VIEs as of September 30, 2018 and December 31, 2017 , respectively: September 30, 2018 Debt Outstanding Carrying Amount of Assets Securing Debt Outstanding Short-Term Long-Term Total Loans Restricted Cash Other Assets (1) Total Secured borrowings: Private Education Loan term securitizations $ — $ 4,335,075 $ 4,335,075 $ 5,174,592 $ 111,555 $ 381,760 $ 5,667,907 ABCP Facility — — — — — 430 430 Total $ — $ 4,335,075 $ 4,335,075 $ 5,174,592 $ 111,555 $ 382,190 $ 5,668,337 December 31, 2017 Debt Outstanding Carrying Amount of Assets Securing Debt Outstanding Short-Term Long-Term Total Loans Restricted Cash Other Assets (1) Total Secured borrowings: Private Education Loan term securitizations $ — $ 3,078,731 $ 3,078,731 $ 3,691,024 $ 95,966 $ 240,208 $ 4,027,198 ABCP Facility — — — — 1,017 161 1,178 Total $ — $ 3,078,731 $ 3,078,731 $ 3,691,024 $ 96,983 $ 240,369 $ 4,028,376 ____

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Impact of derivatives on the consolidated balance sheet	The following tables summarize the fair values and notional amounts of all derivative instruments at September 30, 2018 and December 31, 2017 , and their impact on earnings and other comprehensive income for the three and nine months ended September 30, 2018 and 2017. Please refer to Note 11, “Derivative Financial Instruments” in our 2017 Form 10-K for a full discussion of cash flow hedges, fair value hedges, and trading activities. Impact of Derivatives on the Consolidated Balance Sheet Cash Flow Hedges Fair Value Hedges Trading Total September 30, December 31, September 30, December September 30, December September 30, December 2018 2017 2018 2017 2018 2017 2018 2017 Fair Values (1) Hedged Risk Exposure Derivative Assets: (2) Interest rate swaps Interest rate $ — $ — $ 1,306 $ 630 $ 78 $ 182 $ 1,384 $ 812 Derivative Liabilities: (2) Interest rate swaps Interest rate (454 ) (2,584 ) — — — — (454 ) (2,584 ) Total net derivatives $ (454 ) $ (2,584 ) $ 1,306 $ 630 $ 78 $ 182 $ 930 $ (1,772 ) ___________ (1) Fair values reported include variation margin as legal settlement of the derivative contract and accrued interest. Assets and liabilities are presented without consideration of master netting agreements. Derivatives are carried on the balance sheet based on net position by counterparty under master netting agreements and classified in other assets or other liabilities depending on whether in a net positive or negative position. (2) The following table reconciles gross positions with the impact of master netting agreements to the balance sheet classification: Other Assets Other Liabilities September 30, December 31, September 30, December 31, 2018 2017 2018 2017 Gross position (1) $ 1,384 $ 812 $ (454 ) $ (2,584 ) Impact of master netting agreement (340 ) (812 ) 340 812 Derivative values with impact of master netting agreements (as carried on balance sheet) 1,044 — (114 ) (1,772 ) Cash collateral pledged (2) 32,071 — — 21,586 Net position $ 33,115 $ — $ (114 ) $ 19,814 __________ (1) Gross position amounts include accrued interest and variation margin as legal settlement of the derivative contract. (2) Cash collateral pledged excludes amounts that represent legal settlement of the derivative contracts.
Offsetting assets	The following table reconciles gross positions with the impact of master netting agreements to the balance sheet classification: Other Assets Other Liabilities September 30, December 31, September 30, December 31, 2018 2017 2018 2017 Gross position (1) $ 1,384 $ 812 $ (454 ) $ (2,584 ) Impact of master netting agreement (340 ) (812 ) 340 812 Derivative values with impact of master netting agreements (as carried on balance sheet) 1,044 — (114 ) (1,772 ) Cash collateral pledged (2) 32,071 — — 21,586 Net position $ 33,115 $ — $ (114 ) $ 19,814 __________ (1) Gross position amounts include accrued interest and variation margin as legal settlement of the derivative contract. (2)
Offsetting liabilities	The following table reconciles gross positions with the impact of master netting agreements to the balance sheet classification: Other Assets Other Liabilities September 30, December 31, September 30, December 31, 2018 2017 2018 2017 Gross position (1) $ 1,384 $ 812 $ (454 ) $ (2,584 ) Impact of master netting agreement (340 ) (812 ) 340 812 Derivative values with impact of master netting agreements (as carried on balance sheet) 1,044 — (114 ) (1,772 ) Cash collateral pledged (2) 32,071 — — 21,586 Net position $ 33,115 $ — $ (114 ) $ 19,814 __________ (1) Gross position amounts include accrued interest and variation margin as legal settlement of the derivative contract. (2) Cash collateral pledged excludes amounts that represent legal settlement of the derivative contracts.
Schedule of notional amounts of outstanding derivative positions	Cash Flow Fair Value Trading Total September 30, December 31, September 30, December 31, September 30, December 31, September 30, December 31, 2018 2017 2018 2017 2018 2017 2018 2017 Notional Values Interest rate swaps $ 1,312,573 $ 1,408,649 $ 4,310,694 $ 3,062,849 $ 1,577,978 $ 987,577 $ 7,201,245 $ 5,459,075
Schedule of Fair Value Hedging Instruments, Statements of Financial Performance and Financial Position, Location	As of September 30, 2018, and December 31, 2017, the following amounts were recorded on the consolidated balance sheet related to cumulative basis adjustments for fair value hedges: Line Item in the Balance Sheet in Which the Hedged Item is Included: Carrying Amount of the Hedged Assets/(Liabilities) Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Assets/(Liabilities) September 30, December 31, September 30, December 31, 2018 2017 2018 2017 Deposits $ (4,251,414 ) $ (3,036,671 ) $ 49,694 $ 22,168
Derivative instruments, gain (loss)	Impact of Derivatives on the Consolidated Statements of Income Three Months Ended Nine Months Ended 2018 2017 2018 2017 Fair Value Hedges Interest rate swaps: Hedged items recorded in interest expense $ 4,809 $ 3,294 $ 27,526 $ 2,673 Derivatives recorded in interest expense (4,896 ) (546 ) (27,774 ) (7,803 ) Total $ (87 ) $ 2,748 $ (248 ) $ (5,130 ) Cash Flow Hedges Interest rate swaps: Amount of gain (loss) reclassified from accumulated other comprehensive income into interest expense $ (21 ) $ (2,689 ) $ (2,142 ) $ (8,697 ) Total $ (21 ) $ (2,689 ) $ (2,142 ) $ (8,697 ) Trading Interest rate swaps: Change in fair value of future interest payments recorded in earnings $ (1,557 ) $ (247 ) $ (8,492 ) $ (1,189 ) Total (1,557 ) (247 ) (8,492 ) (1,189 ) Total $ (1,665 ) $ (188 ) $ (10,882 ) $ (15,016 )
Schedule of derivative instruments, effect on other comprehensive income (loss)	Impact of Derivatives on the Statements of Changes in Stockholders’ Equity Three Months Ended Nine Months Ended September 30, September 30, 2018 2017 2018 2017 Amount of gain recognized in other comprehensive income (loss) $ 6,453 $ 2,125 $ 34,718 $ (1,133 ) Less: amount of loss reclassified in interest expense (21 ) (2,689 ) (2,142 ) (8,697 ) Total change in other comprehensive income (loss) for unrealized gains (losses) on derivatives, before income tax (expense) benefit $ 6,474 $ 4,814 $ 36,860 $ 7,564

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Schedule of common share repurchases	The following table summarizes our common share repurchases and issuances. Three Months Ended Nine Months Ended (Shares and per share amounts in actuals) 2018 2017 2018 2017 Shares repurchased related to employee stock-based compensation plans (1)(2) 116,151 81,817 3,056,746 2,666,781 Average purchase price per share $ 11.54 $ 10.93 $ 11.34 $ 12.09 Common shares issued (3) 397,004 423,112 6,341,950 5,652,886 __________________ (1) Comprised of shares withheld from stock option exercises and vesting of restricted stock for employees’ tax withholding obligations and shares tendered by employees to satisfy option exercise costs. (2) At the present time, we do not intend to initiate a publicly announced share repurchase program. (3)

Earnings per Common Share (Tabl

Earnings per Common Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Schedule of earnings per share, basic and diluted	A reconciliation of the numerators and denominators of the basic and diluted EPS calculations follows. Three Months Ended Nine Months Ended September 30, September 30, (In thousands, except per share data) 2018 2017 2018 2017 Numerator: Net income $ 103,878 $ 76,371 $ 339,964 $ 241,931 Preferred stock dividends 4,124 3,028 11,441 12,577 Net income attributable to SLM Corporation common stock $ 99,754 $ 73,343 $ 328,523 $ 229,354 Denominator: Weighted average shares used to compute basic EPS 435,468 431,718 434,875 430,958 Effect of dilutive securities: Dilutive effect of stock options, restricted stock, restricted stock units and Employee Stock Purchase Plan (“ESPP”) (1)(2) 4,551 6,701 4,609 7,464 Weighted average shares used to compute diluted EPS 440,019 438,419 439,484 438,422 Basic earnings per common share attributable to SLM Corporation $ 0.23 $ 0.17 $ 0.76 $ 0.53 Diluted earnings per common share attributable to SLM Corporation $ 0.23 $ 0.17 $ 0.75 $ 0.52 ________________ (1) Includes the potential dilutive effect of additional common shares that are issuable upon exercise of outstanding stock options, restricted stock, restricted stock units, and the outstanding commitment to issue shares under the ESPP, determined by the treasury stock method. (2) For the three months ended September 30, 2018 and 2017, securities covering approximately 0 and 0 shares, respectively, and for the nine months ended September 30, 2018 and 2017, securities covering approximately 0 and 0

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Valuation of financial instruments that are marked-to-market on recurring basis	The following table summarizes the valuation of our financial instruments that are marked to fair value on a recurring basis. Fair Value Measurements on a Recurring Basis September 30, 2018 December 31, 2017 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Available-for-sale investments $ — $ 172,370 $ — $ 172,370 $ — $ 244,088 $ — $ 244,088 Derivative instruments — 1,384 — 1,384 — 812 — 812 Total $ — $ 173,754 $ — $ 173,754 $ — $ 244,900 $ — $ 244,900 Liabilities Derivative instruments $ — $ (454 ) $ — $ (454 ) $ — $ (2,584 ) $ — $ (2,584 ) Total $ — $ (454 ) $ — $ (454 ) $ — $ (2,584 ) $ — $ (2,584 )
Fair values of financial assets and liabilities, including derivative financial instruments	The following table summarizes the fair values of our financial assets and liabilities, including derivative financial instruments. September 30, 2018 December 31, 2017 Fair Value Carrying Value Difference Fair Value Carrying Value Difference Earning assets Loans held for investment, net $ 24,167,452 $ 21,978,903 $ 2,188,549 $ 20,673,136 $ 18,567,641 $ 2,105,495 Cash and cash equivalents 1,839,054 1,839,054 — 1,534,339 1,534,339 — Available-for-sale investments 172,370 172,370 — 244,088 244,088 — Accrued interest receivable 1,270,026 1,270,026 — 967,482 967,482 — Tax indemnification receivable 54,941 54,941 — 168,011 168,011 — Derivative instruments 1,384 1,384 — 812 812 — Total earning assets $ 27,505,227 $ 25,316,678 $ 2,188,549 $ 23,587,868 $ 21,482,373 $ 2,105,495 Interest-bearing liabilities Money-market and savings accounts $ 8,923,893 $ 8,923,893 $ — $ 8,470,209 $ 8,470,209 $ — Certificates of deposit 8,928,356 8,948,888 20,532 7,044,208 7,034,121 (10,087 ) Long-term borrowings 4,503,254 4,532,221 28,967 3,299,871 3,275,270 (24,601 ) Accrued interest payable 62,627 62,627 — 35,363 35,363 — Derivative instruments 454 454 — 2,584 2,584 — Total interest-bearing liabilities $ 22,418,584 $ 22,468,083 $ 49,499 $ 18,852,235 $ 18,817,547 $ (34,688 ) Excess of net asset fair value over carrying value $ 2,238,048 $ 2,070,807

Regulatory Capital (Tables)

Regulatory Capital (Tables)	9 Months Ended
	Sep. 30, 2018
Banking and Thrift [Abstract]
Schedule of compliance with regulatory capital requirements under banking regulations	The following capital amounts and ratios are based upon the Bank’s assets. Actual “Well Capitalized” Amount Ratio Amount Ratio As of September 30, 2018: Common Equity Tier 1 Capital (to Risk-Weighted Assets) $ 2,735,622 11.5 % $ 1,541,678 > 6.5 % Tier 1 Capital (to Risk-Weighted Assets) $ 2,735,622 11.5 % $ 1,897,450 > 8.0 % Total Capital (to Risk-Weighted Assets) $ 3,032,522 12.8 % $ 2,371,812 > 10.0 % Tier 1 Capital (to Average Assets) $ 2,735,622 11.1 % $ 1,233,163 > 5.0 % As of December 31, 2017: Common Equity Tier 1 Capital (to Risk-Weighted Assets) $ 2,350,081 11.9 % $ 1,288,435 > 6.5 % Tier 1 Capital (to Risk-Weighted Assets) $ 2,350,081 11.9 % $ 1,585,767 > 8.0 % Total Capital (to Risk-Weighted Assets) $ 2,597,926 13.1 % $ 1,982,208 > 10.0 % Tier 1 Capital (to Average Assets) $ 2,350,081 11.0 % $ 1,067,739 > 5.0 %

Significant Accounting Polices

Significant Accounting Polices (Details) - USD ($) $ in Thousands	Jul. 01, 2018	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Significant Accounting Policies [Line Items]
Loss expected to be reclassified to interest expense in next 12 months					$ 7,000
Increase to hedged deposit balances		$ 33,000			33,000		$ 20,000
Cumulative effect of adoption of accounting principle								$ 165
(Losses) gains on derivatives and hedging activities, net		(4,949)		$ 1,661	(6,325)	$ (7,326)
Retained Earnings
Significant Accounting Policies [Line Items]
Cumulative effect of adoption of accounting principle								$ (264)
Reclassification resulting from the adoption of tax cuts and jobs act			$ 600		(592)
Accumulated Other Comprehensive Income
Significant Accounting Policies [Line Items]
Reclassification resulting from the adoption of tax cuts and jobs act			$ 600		592
Accounting Standards Update 2017-12
Significant Accounting Policies [Line Items]
Cumulative effect of adoption of accounting principle							1,052
Accounting Standards Update 2017-12 | Retained Earnings
Significant Accounting Policies [Line Items]
Cumulative effect of adoption of accounting principle							782
Accounting Standards Update 2017-12 | Accumulated Other Comprehensive Income
Significant Accounting Policies [Line Items]
Cumulative effect of adoption of accounting principle							$ 270
Fair Value Hedges | Accounting Standards Update 2017-12
Significant Accounting Policies [Line Items]
Increase to hedged deposit balances	$ 2,000
(Losses) gains on derivatives and hedging activities, net	(3,000)
Fair Value Hedges | Accounting Standards Update 2017-12 | Retained Earnings
Significant Accounting Policies [Line Items]
Cumulative effect of adoption of accounting principle	$ 1,000
Cash Flow Hedges | Accounting Standards Update 2017-12 | Retained Earnings
Significant Accounting Policies [Line Items]
Cumulative effect of adoption of accounting principle		(300)			(300)
Cash Flow Hedges | Accounting Standards Update 2017-12 | Accumulated Other Comprehensive Income
Significant Accounting Policies [Line Items]
Cumulative effect of adoption of accounting principle		$ 300			$ 300

Investments - Schedule of Amort

Investments - Schedule of Amortized Cost and Fair Value of Securities Available-for-sale (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Available for sale:
Amortized Cost	$ 181,785	$ 247,607
Gross Unrealized Gains	92	650
Gross Unrealized Losses	(9,507)	(4,169)
Available-for-sale investments	172,370	244,088
Mortgage-backed securities
Available for sale:
Amortized Cost	159,397	227,607
Gross Unrealized Gains	92	650
Gross Unrealized Losses	(8,046)	(3,210)
Available-for-sale investments	151,443	225,047
Utah Housing Corporation bonds
Available for sale:
Amortized Cost	22,388	20,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,461)	(959)
Available-for-sale investments	$ 20,927	$ 19,041

Investments - Unrealized Losses

Investments - Unrealized Losses and Fair Value for Mortgage-Backed Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Less than 12 months
Gross Unrealized Losses	$ (1,893)	$ (849)
Estimated Fair Value	48,128	82,279
12 months or more
Gross Unrealized Losses	(7,614)	(3,320)
Estimated Fair Value	120,893	124,618
Gross Unrealized Losses	(9,507)	(4,169)
Estimated Fair Value	169,021	206,897
Mortgage-backed securities
Less than 12 months
Gross Unrealized Losses	(1,768)	(772)
Estimated Fair Value	43,253	77,356
12 months or more
Gross Unrealized Losses	(6,278)	(2,438)
Estimated Fair Value	104,841	110,500
Gross Unrealized Losses	(8,046)	(3,210)
Estimated Fair Value	148,094	187,856
Utah Housing Corporation bonds
Less than 12 months
Gross Unrealized Losses	(125)	(77)
Estimated Fair Value	4,875	4,923
12 months or more
Gross Unrealized Losses	(1,336)	(882)
Estimated Fair Value	16,052	14,118
Gross Unrealized Losses	(1,461)	(959)
Estimated Fair Value	$ 20,927	$ 19,041

Investments - Narrative (Detail

Investments - Narrative (Details) $ in Thousands	3 Months Ended
	Jun. 30, 2018USD ($)security	Sep. 30, 2018USD ($)security	Dec. 31, 2017USD ($)security
Debt Securities, Available-for-sale [Line Items]
Amortized cost		$ 181,785	$ 247,607
Ginnie Mae
Debt Securities, Available-for-sale [Line Items]
Amortized cost		68,000
Fannie Mae
Debt Securities, Available-for-sale [Line Items]
Amortized cost		47,000
Freddie Mac
Debt Securities, Available-for-sale [Line Items]
Amortized cost		44,000
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized cost		$ 159,397	$ 227,607
Number of mortgage-backed securities sold | security	9
Securities sold to align the portfolio with the Community Reinvestment Act requirements	$ 41,000
Recognized loss on securities	$ 2,000
Number of mortgage-backed securities with unrealized losses | security		75	62
Number of mortgage-backed securities | security		84	92
Par value of mortgage-backed securities pledged		$ 153,000	$ 218,000
Mortgage-backed securities | Ginnie Mae
Debt Securities, Available-for-sale [Line Items]
Number of mortgage-backed securities with unrealized losses | security		35	31
Utah Housing Corporation bonds
Debt Securities, Available-for-sale [Line Items]
Amortized cost		$ 22,388	$ 20,000
Moody's, Aa3 Rating | Utah Housing Corporation bonds
Debt Securities, Available-for-sale [Line Items]
Amortized cost basis		$ 22,000	$ 20,000

Investments - Schedule of Matur

Investments - Schedule of Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 181,785	$ 247,607
Available-for-sale investments	172,370	$ 244,088
2,038
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	267
Available-for-sale investments	281
2,039
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,990
Available-for-sale investments	3,068
2,042
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	9,524
Available-for-sale investments	8,766
2,043
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	14,396
Available-for-sale investments	13,728
2,044
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	23,437
Available-for-sale investments	22,535
2,045
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	25,868
Available-for-sale investments	24,468
2,046
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	40,006
Available-for-sale investments	37,703
2,047
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	57,395
Available-for-sale investments	54,082
2,048
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	7,902
Available-for-sale investments	$ 7,739

Loans Held for Investment - Add

Loans Held for Investment - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Jul. 01, 2006	Jun. 30, 2006	Sep. 30, 1993
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of private loans indexed to LIBOR	69.00%			69.00%		77.00%
Gain on sale of portfolio split loans	$ 0		$ 0	$ 2,060	$ 0
Tier 1 of government guarantee (in percentage)	97.00%			97.00%			97.00%
Tier 2 of government guarantee (in percentage)								98.00%
Tier 3 of government guarantee (in percentage)									100.00%
Estimated weighted average life of student loans (in years)				5 years 4 months 24 days		5 years 6 months
Discontinued Operations, Disposed of by Sale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portfolio split loans sold		$ 43,000
Gain on sale of portfolio split loans		$ 2,000

Loans Held for Investment - Stu

Loans Held for Investment - Student Loan Portfolio by Program (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses	$ (328,974)	$ (295,277)	$ (251,475)	$ (229,919)	$ (207,448)	$ (184,701)
Loans held for investment, net	21,978,903		18,567,641
Private Education Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross amount of loans	20,239,991		17,432,167
Deferred origination costs and unamortized premium/(discount)	65,499		56,378
Allowance for loan losses	(274,684)		(243,715)
Loans held for investment, net	20,030,806		17,244,830
Private Education Loans | Fixed rate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross amount of loans	6,369,950		4,000,447
Private Education Loans | Variable rate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross amount of loans	13,870,041		13,431,720
FFELP Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross amount of loans	866,786		927,660
Deferred origination costs and unamortized premium/(discount)	2,432		2,631
Allowance for loan losses	(1,080)		(1,132)
Loans held for investment, net	868,138		929,159
Personal Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross amount of loans	1,133,005		400,280
Deferred origination costs and unamortized premium/(discount)	164		0
Allowance for loan losses	(53,210)		(6,628)
Loans held for investment, net	$ 1,079,959		$ 393,652

Loans Held for Investment - S_2

Loans Held for Investment - Student Loan Portfolio Average Balances (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Balance	$ 21,254,774	$ 17,275,377	$ 20,617,890	$ 16,833,926
Private Education Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Balance	$ 19,295,318	$ 16,228,751	$ 18,908,929	$ 15,791,557
Weighted Average Interest Rate	9.16%	8.50%	9.01%	8.37%
FFELP Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Balance	$ 877,279	$ 960,185	$ 898,208	$ 981,106
Weighted Average Interest Rate	4.65%	4.02%	4.47%	3.86%
Personal Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Average Balance	$ 1,082,177	$ 86,441	$ 810,753	$ 61,263
Weighted Average Interest Rate	11.03%	9.66%	10.82%	9.44%

Allowance for Loan Losses - All

Allowance for Loan Losses - Allowance and Recorded Investments in Loans (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)charge_off	Sep. 30, 2017USD ($)charge_off	Sep. 30, 2018USD ($)charge_off	Sep. 30, 2017USD ($)charge_off
Allowance for Loan Losses
Allowance at beginning of period	$ 295,277	$ 207,448	$ 251,475	$ 184,701
Total provision	68,896	53,847	187,339	130,524
Net charge-offs:
Charge-offs	(40,221)	(34,681)	(124,458)	(94,133)
Recoveries	5,022	4,562	15,834	12,218
Net charge-offs	(35,199)	(30,119)	(108,624)	(81,915)
Loan sales	0	(1,257)	(1,216)	(3,391)
Allowance at end of period	328,974	229,919	328,974	229,919
Allowance:
Ending balance: individually evaluated for impairment	119,643	100,999	119,643	100,999
Ending balance: collectively evaluated for impairment	209,331	128,920	209,331	128,920
Loans:
Ending balance: individually evaluated for impairment	1,199,493	942,561	1,199,493	942,561
Ending balance: collectively evaluated for impairment	21,040,289	17,271,626	21,040,289	17,271,626
FFELP Loans
Allowance for Loan Losses
Allowance at beginning of period	1,073	1,606	1,132	2,171
Total provision	259	(73)	742	(161)
Net charge-offs:
Charge-offs	(252)	(181)	(794)	(658)
Recoveries	0	0	0	0
Net charge-offs	(252)	(181)	(794)	(658)
Loan sales	0	0	0	0
Allowance at end of period	1,080	1,352	1,080	1,352
Allowance:
Ending balance: individually evaluated for impairment	0	0	0	0
Ending balance: collectively evaluated for impairment	1,080	1,352	1,080	1,352
Loans:
Ending balance: individually evaluated for impairment	0	0	0	0
Ending balance: collectively evaluated for impairment	$ 866,786	$ 949,180	$ 866,786	$ 949,180
Net charge-offs as a percentage of average loans in repayment (annualized)	0.15%	0.10%	0.15%	0.12%
Allowance as a percentage of the ending total loan balance	0.12%	0.14%	0.12%	0.14%
Allowance as a percentage of the ending loans in repayment	0.16%	0.20%	0.16%	0.20%
Allowance coverage of net charge-offs (annualized) | charge_off	1.07	1.87	1.02	1.54
Ending total loans, gross	$ 866,786	$ 949,180	$ 866,786	$ 949,180
Average loans in repayment	681,131	734,613	700,679	752,990
Ending loans in repayment	679,110	690,849	679,110	690,849
Private Education Loans
Allowance for Loan Losses
Allowance at beginning of period	261,695	205,024	243,715	182,472
Total provision	42,482	53,120	130,616	129,105
Net charge-offs:
Charge-offs	(34,229)	(34,280)	(113,852)	(93,235)
Recoveries	4,736	4,560	15,421	12,216
Net charge-offs	(29,493)	(29,720)	(98,431)	(81,019)
Loan sales	0	(1,257)	(1,216)	(3,391)
Allowance at end of period	274,684	227,167	274,684	227,167
Allowance:
Ending balance: individually evaluated for impairment	119,643	100,999	119,643	100,999
Ending balance: collectively evaluated for impairment	155,041	126,168	155,041	126,168
Loans:
Ending balance: individually evaluated for impairment	1,199,493	942,561	1,199,493	942,561
Ending balance: collectively evaluated for impairment	$ 19,040,498	$ 16,190,346	$ 19,040,498	$ 16,190,346
Net charge-offs as a percentage of average loans in repayment (annualized)	0.88%	1.08%	1.01%	1.02%
Allowance as a percentage of the ending total loan balance	1.36%	1.33%	1.36%	1.33%
Allowance as a percentage of the ending loans in repayment	1.99%	1.99%	1.99%	1.99%
Allowance coverage of net charge-offs (annualized) | charge_off	2.33	1.91	2.09	2.10
Ending total loans, gross	$ 20,239,991	$ 17,132,907	$ 20,239,991	$ 17,132,907
Average loans in repayment	13,351,517	10,971,028	13,009,704	10,589,725
Ending loans in repayment	13,815,415	11,406,581	13,815,415	11,406,581
Personal Loans
Allowance for Loan Losses
Allowance at beginning of period	32,509	818	6,628	58
Total provision	26,155	800	55,981	1,580
Net charge-offs:
Charge-offs	(5,740)	(220)	(9,812)	(240)
Recoveries	286	2	413	2
Net charge-offs	(5,454)	(218)	(9,399)	(238)
Loan sales	0	0	0	0
Allowance at end of period	53,210	1,400	53,210	1,400
Allowance:
Ending balance: individually evaluated for impairment	0	0	0	0
Ending balance: collectively evaluated for impairment	53,210	1,400	53,210	1,400
Loans:
Ending balance: individually evaluated for impairment	0	0	0	0
Ending balance: collectively evaluated for impairment	$ 1,133,005	$ 132,100	$ 1,133,005	$ 132,100
Net charge-offs as a percentage of average loans in repayment (annualized)	2.03%	0.96%	1.56%	0.51%
Allowance as a percentage of the ending total loan balance	4.70%	1.06%	4.70%	1.06%
Allowance as a percentage of the ending loans in repayment	4.70%	1.06%	4.70%	1.06%
Allowance coverage of net charge-offs (annualized) | charge_off	2.44	1.60	4.25	4.41
Ending total loans, gross	$ 1,133,005	$ 132,100	$ 1,133,005	$ 132,100
Average loans in repayment	1,072,624	90,850	803,928	62,747
Ending loans in repayment	$ 1,133,005	$ 132,100	$ 1,133,005	$ 132,100

Allowance for Loan Losses - Add

Allowance for Loan Losses - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jul. 01, 2006
Receivables [Abstract]
Interest rate offered to borrowers facing financial difficulty	2.00%
Term of interest rate offered to borrowers facing financial difficulty	2 years
Percentage of loans in full and interest repayment status that are subject to interest rate reductions	7.40%		5.20%
Percentage of loans granted forbearance qualified as TDR	58.00%	66.00%
Criteria for loans to be considered as nonperforming (greater than)	90 days
Tier 1 of government guarantee (at least) (in percentage)	97.00%			97.00%
TDR payment default period (more than)	60 days
Percentage of FFELP loans insured and guaranteed (at least)	97.00%
Period of loans past due that have accrued interest (greater than)	90 days

Allowance for Loan Losses - Rec

Allowance for Loan Losses - Recorded Investment, Unpaid Principal Balance and Related Allowance for TDR Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Receivables [Abstract]
Recorded Investment	$ 1,220,233	$ 1,007,141
Unpaid Principal Balance	1,199,493	990,351
Allowance	$ 119,643	$ 94,682

Allowance for Loan Losses - Ave

Allowance for Loan Losses - Average Recorded Investment and Interest Income Recognized for TDR (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Receivables [Abstract]
Average Recorded Investment	$ 1,180,206	$ 877,011	$ 1,106,946	$ 772,362
Interest Income Recognized	$ 19,943	$ 16,517	$ 56,509	$ 43,084

Allowance for Loan Losses - Loa

Allowance for Loan Losses - Loan Status and Aging of Past Due TDR Loans (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
TDR loans in repayment and percentage of each status:
Allowance for loan losses	$ (328,974)	$ (295,277)	$ (251,475)	$ (229,919)	$ (207,448)	$ (184,701)
Loans held for investment, net	21,978,903		18,567,641
Student Loan | Consumer Portfolio Segment | Troubled Debt Restructured Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
TDR loans in in-school/grace/deferment	68,848		51,745
TDR loans in forbearance	73,403		69,652
TDR loans in repayment and percentage of each status:
Loans current	954,309		774,222
Total TDR loans in repayment	$ 1,057,242		$ 868,954
Loans current (as a percentage)	90.30%		89.10%
Total TDR loans in repayment	100.00%		100.00%
Total Private Education Loans, gross	$ 1,199,493		$ 990,351
Student Loan | Consumer Portfolio Segment | Loans delinquent 31-60 days | Troubled Debt Restructured Loans
TDR loans in repayment and percentage of each status:
Loans delinquent	$ 51,979		$ 48,377
Loans delinquent (as a percentage)	4.90%		5.60%
Student Loan | Consumer Portfolio Segment | Loans delinquent 61-90 days | Troubled Debt Restructured Loans
TDR loans in repayment and percentage of each status:
Loans delinquent	$ 31,582		$ 28,778
Loans delinquent (as a percentage)	3.00%		3.30%
Student Loan | Consumer Portfolio Segment | Loans delinquent, greater than 90 days | Troubled Debt Restructured Loans
TDR loans in repayment and percentage of each status:
Loans delinquent	$ 19,372		$ 17,577
Loans delinquent (as a percentage)	1.80%		2.00%

Allowance for Loan Losses - Mod

Allowance for Loan Losses - Modified Loan Accounts for TDR (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Receivables [Abstract]
Modified Loans	$ 101,117	$ 168,645	$ 301,769	$ 415,341
Charge-offs	11,090	12,227	39,315	34,965
Payment Default	$ 20,595	$ 28,275	$ 68,430	$ 77,248

Allowance for Loan Losses - L_2

Allowance for Loan Losses - Loan Portfolio Stratified by Key Credit Quality Indicators (Detail) - Consumer Portfolio Segment - Student Loan - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Private Education Loans | With Cosigner
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 18,147,180	$ 15,658,539
Private Education Loans with cosigner (in percentage)	90.00%	90.00%
Private Education Loans | Without Cosigner
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 2,092,811	$ 1,773,628
Private Education Loans without cosigner (in percentage)	10.00%	10.00%
Private Education Loans | Cosigners
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 20,239,991	$ 17,432,167
Total in percent	100.00%	100.00%
Private Education Loans | FICO at Original Approval
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 20,239,991	$ 17,432,167
Total in percent	100.00%	100.00%
Private Education Loans | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 20,239,991	$ 17,432,167
Total in percent	100.00%	100.00%
Seasoning based on monthly scheduled payments due from 1-12 payments (in percentage)	27.00%	24.00%
Seasoning based on monthly scheduled payments due from 13 - 24 payments (in percentage)	16.00%	19.00%
Seasoning based on monthly scheduled payments due from 25 - 36 payments (in percentage)	13.00%	14.00%
Seasoning based on monthly scheduled payments due from 37 - 48 payments (in percentage)	8.00%	9.00%
Seasoning based on monthly scheduled payments due from more than 48 payments (in percentage)	7.00%	7.00%
Seasoning based on monthly scheduled payments due from not yet in repayment (in percentage)	29.00%	27.00%
Private Education Loans | FICO score less than 670 | FICO at Original Approval
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 1,373,155	$ 1,153,591
Private Education Loans At Origination	7.00%	6.00%
Private Education Loans | FICO score 670-699 | FICO at Original Approval
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 3,042,228	$ 2,596,959
Private Education Loans At Origination	15.00%	15.00%
Private Education Loans | FICO score 700-749 | FICO at Original Approval
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 6,655,405	$ 5,714,554
Private Education Loans At Origination	33.00%	33.00%
Private Education Loans | FICO score greater than or equal to 750 | FICO at Original Approval
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 9,169,203	$ 7,967,063
Private Education Loans At Origination	45.00%	46.00%
Private Education Loans | 1-12 payments | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 5,419,487	$ 4,256,592
Private Education Loans | 13-24 payments | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	3,238,910	3,229,465
Private Education Loans | 25-36 payments | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	2,533,308	2,429,238
Private Education Loans | 37-48 payments | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	1,638,309	1,502,327
Private Education Loans | More than 48 payments | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	1,473,944	1,256,813
Private Education Loans | Not yet in repayment | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	5,936,033	4,757,732
Personal Loans | FICO at Original Approval
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 1,133,005	$ 400,280
Total in percent	100.00%	100.00%
Personal Loans | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 1,133,005	$ 400,280
Total in percent	100.00%	100.00%
Seasoning based on monthly scheduled payments due from 1-12 payments (in percentage)	96.00%	100.00%
Seasoning based on monthly scheduled payments due from 13 - 24 payments (in percentage)	4.00%	0.00%
Seasoning based on monthly scheduled payments due from 25 - 36 payments (in percentage)	0.00%	0.00%
Seasoning based on monthly scheduled payments due from 37 - 48 payments (in percentage)	0.00%	0.00%
Seasoning based on monthly scheduled payments due from more than 48 payments (in percentage)	0.00%	0.00%
Personal Loans | FICO score less than 670 | FICO at Original Approval
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 79,769	$ 32,156
Private Education Loans At Origination	7.00%	8.00%
Personal Loans | FICO score 670-699 | FICO at Original Approval
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 327,364	$ 114,731
Private Education Loans At Origination	29.00%	29.00%
Personal Loans | FICO score 700-749 | FICO at Original Approval
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 520,370	$ 182,025
Private Education Loans At Origination	46.00%	45.00%
Personal Loans | FICO score greater than or equal to 750 | FICO at Original Approval
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 205,502	$ 71,368
Private Education Loans At Origination	18.00%	18.00%
Personal Loans | 1-12 payments | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 1,084,706	$ 400,280
Personal Loans | 13-24 payments | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	48,299	0
Personal Loans | 25-36 payments | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	0	0
Personal Loans | 37-48 payments | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	0	0
Personal Loans | More than 48 payments | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 0	$ 0

Allowance for Loan Losses - Age

Allowance for Loan Losses - Age Analysis of Past Due Loans Delinquencies (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Loans in repayment and percentage of each status:
Private Education Loans allowance for losses	$ (328,974)	$ (295,277)	$ (251,475)	$ (229,919)	$ (207,448)	$ (184,701)
Loans held for investment, net	21,978,903		18,567,641
Private Education Loans
Loans in repayment and percentage of each status:
Private Education Loans deferred origination costs	65,499		56,378
Total Private Education Loans, gross	20,239,991		17,432,167
Private Education Loans allowance for losses	(274,684)		(243,715)
Loans held for investment, net	20,030,806		17,244,830
Private Education Loans | Consumer Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans in-school/grace/deferment	5,936,033		4,757,732
Loans in forbearance	488,543		468,402
Loans in repayment and percentage of each status:
Loans current	$ 13,492,029		$ 11,911,128
Loans current (as a percentage)	97.70%		97.60%
Total TDR loans in repayment	$ 13,815,415		$ 12,206,033
Total TDR loans in repayment (as a percentage)	100.00%		100.00%
Private Education Loans deferred origination costs	$ 65,499		$ 56,378
Total Private Education Loans, gross	20,305,490		17,488,545
Total Private Education Loans, gross	20,239,991		17,432,167
Private Education Loans allowance for losses	(274,684)		(243,715)
Loans held for investment, net	$ 20,030,806		$ 17,244,830
Percentage of Private Education Loans in repayment	68.30%		70.00%
Delinquencies as a percentage of Private Education Loans in repayment	2.30%		2.40%
Loans in forbearance as a percentage of Private Education Loans in repayment and forbearance	3.40%		3.70%
Private Education Loans | Consumer Portfolio Segment | Loans delinquent 31-60 days
Loans in repayment and percentage of each status:
Loans delinquent	$ 198,987		$ 179,002
Loans delinquent (as a percentage)	1.40%		1.50%
Private Education Loans | Consumer Portfolio Segment | Loans delinquent 61-90 days
Loans in repayment and percentage of each status:
Loans delinquent	$ 82,358		$ 78,292
Loans delinquent (as a percentage)	0.60%		0.60%
Private Education Loans | Consumer Portfolio Segment | Loans delinquent, greater than 90 days
Loans in repayment and percentage of each status:
Loans delinquent	$ 42,041		$ 37,611
Loans delinquent (as a percentage)	0.30%		0.30%
Personal Loans
Loans in repayment and percentage of each status:
Private Education Loans deferred origination costs	$ 164		$ 0
Total Private Education Loans, gross	1,133,005		400,280
Private Education Loans allowance for losses	(53,210)		(6,628)
Loans held for investment, net	1,079,959		393,652
Personal Loans | Consumer Portfolio Segment
Loans in repayment and percentage of each status:
Loans current	$ 1,123,597		$ 398,988
Loans current (as a percentage)	99.20%		99.70%
Total TDR loans in repayment	$ 1,133,005		$ 400,280
Total TDR loans in repayment (as a percentage)	100.00%		100.00%
Private Education Loans deferred origination costs	$ 164		$ 0
Total Private Education Loans, gross	1,133,169		400,280
Total Private Education Loans, gross	1,133,005		400,280
Private Education Loans allowance for losses	(53,210)		(6,628)
Loans held for investment, net	$ 1,079,959		$ 393,652
Delinquencies as a percentage of Private Education Loans in repayment	0.80%		0.30%
Personal Loans | Consumer Portfolio Segment | Loans delinquent 31-60 days
Loans in repayment and percentage of each status:
Loans delinquent	$ 4,321		$ 761
Loans delinquent (as a percentage)	0.40%		0.20%
Personal Loans | Consumer Portfolio Segment | Loans delinquent 61-90 days
Loans in repayment and percentage of each status:
Loans delinquent	$ 2,804		$ 340
Loans delinquent (as a percentage)	0.20%		0.10%
Personal Loans | Consumer Portfolio Segment | Loans delinquent, greater than 90 days
Loans in repayment and percentage of each status:
Loans delinquent	$ 2,283		$ 191
Loans delinquent (as a percentage)	0.20%		0.00%

Allowance for Loan Losses - Acc

Allowance for Loan Losses - Accrued Interest Receivable (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Receivables [Abstract]
Total Interest Receivable	$ 1,250,288	$ 951,138
Greater Than 90 Days Past Due	1,594	1,372
Allowance for Uncollectible Interest	$ 6,462	$ 4,664

Deposits - Summary of Total Dep

Deposits - Summary of Total Deposits (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Banking and Thrift [Abstract]
Deposits - interest bearing	$ 17,872,781	$ 15,504,330
Deposits - non-interest bearing	512	1,053
Total deposits	$ 17,873,293	$ 15,505,383

Deposits - Additional Informati

Deposits - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Banking and Thrift [Abstract]
Deposits	$ 17,873,293		$ 17,873,293		$ 15,505,383
Brokered deposits	9,500,000		9,500,000		8,200,000
Retail and other deposits	8,400,000		8,400,000		7,300,000
Stable interest-bearing deposits, total	5,600,000		5,600,000		5,500,000
Brokered deposit placement fee	4,000	$ 3,000	9,000	$ 7,000
Third party broker fees paid	6,000	$ 4,000	25,000	$ 10,000
Deposits exceeding FDIC insurance limits	420,000		420,000		396,000
Accrued interest on deposits	$ 52,000		$ 52,000		$ 28,000

Deposits - Interest Bearing Dep

Deposits - Interest Bearing Deposits (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Amount
Money market	$ 8,239,595	$ 7,731,966
Savings	684,298	738,243
Certificates of deposit	8,948,888	7,034,121
Deposits - interest bearing	$ 17,872,781	$ 15,504,330
Weighted Average Stated Rate
Money market	2.29%	1.80%
Savings	1.70%	1.10%
Certificates of deposit	2.65%	1.93%

Borrowings - Company Borrowings

Borrowings - Company Borrowings (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Document Period End Date	Sep. 30, 2018
Short Term	$ 0	$ 0
Long Term	4,532,221	3,275,270
Total	4,532,221	3,275,270
Unsecured borrowings
Debt Instrument [Line Items]
Short Term	0	0
Long Term	197,146	196,539
Total	197,146	196,539
Secured borrowings
Debt Instrument [Line Items]
Short Term	0	0
Long Term	4,335,075	3,078,731
Total	4,335,075	3,078,731
Secured borrowings | Private Education Loan securitization
Debt Instrument [Line Items]
Short Term	0	0
Long Term	4,335,075	3,078,731
Total	4,335,075	3,078,731
Secured borrowings | Private Education Loan securitization | Fixed rate
Debt Instrument [Line Items]
Short Term	0	0
Long Term	2,337,004	1,565,760
Total	2,337,004	1,565,760
Secured borrowings | Private Education Loan securitization | Variable rate
Debt Instrument [Line Items]
Short Term	0	0
Long Term	1,998,071	1,512,971
Total	1,998,071	1,512,971
Secured borrowings | ABCP Facility
Debt Instrument [Line Items]
Short Term	0	0
Long Term	0	0
Total	$ 0	$ 0

Borrowings - Additional Informa

Borrowings - Additional Information (Details) - USD ($)	Sep. 19, 2018	Jun. 20, 2018	Mar. 21, 2018	Feb. 21, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Apr. 05, 2017	Dec. 31, 2016
Line of Credit Facility [Line Items]
Short-term borrowings					$ 0		$ 0
Unsecured offering issued					1,900,500,000		$ 1,448,000,000		$ 1,782,000,000
Proceeds from loan securitization sold to third parties					$ 0	$ 197,000,000
Estimated weighted average life of student loans (in years)					5 years 4 months 24 days		5 years 6 months
Uncommitted federal funds					$ 125,000,000
Lendable value of collateral					3,100,000,000		$ 2,600,000,000
ABCP borrowings | Commercial Paper
Line of Credit Facility [Line Items]
Private asset backed commercial paper education loan funding facility				$ 750,000,000
Ownership interest percentage in residual interest in ABCP facility				100.00%
Short-term borrowings					0		0
Private Education Loans 2018 Term A
Line of Credit Facility [Line Items]
Total loan amount securitized at inception			$ 670,000,000
Amount of loan securitization sold to third parties			$ 670,000,000
Ownership interest percentage			100.00%
Proceeds from loan securitization sold to third parties			$ 668,000,000
Loans pledged as collateral					661,000,000
Class A and B Notes
Line of Credit Facility [Line Items]
Estimated weighted average life of student loans (in years)	4 years 3 months 25 days	4 years 4 months 24 days	4 years 5 months 4 days
Private Education Loans 2018 Term B
Line of Credit Facility [Line Items]
Total loan amount securitized at inception		$ 687,000,000
Amount of loan securitization sold to third parties		$ 687,000,000
Ownership interest percentage		100.00%
Proceeds from loan securitization sold to third parties		$ 683,000,000
Loans pledged as collateral					692,000,000
Private Education Loans 2018 Term C
Line of Credit Facility [Line Items]
Total loan amount securitized at inception	$ 544,000,000
Amount of loan securitization sold to third parties	$ 544,000,000
Ownership interest percentage	100.00%
Proceeds from loan securitization sold to third parties	$ 541,000,000
Loans pledged as collateral					555,000,000
LIBOR | ABCP borrowings | Commercial Paper
Line of Credit Facility [Line Items]
Basis spread on variable rate				0.85%
LIBOR | Class A and B Notes
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.77%	0.76%	0.78%
Minimum | ABCP borrowings | Commercial Paper
Line of Credit Facility [Line Items]
Financing cost percentage of unused borrowing capacity				0.35%
Maximum | ABCP borrowings | Commercial Paper
Line of Credit Facility [Line Items]
Financing cost percentage of unused borrowing capacity				0.45%
Unsecured borrowings
Line of Credit Facility [Line Items]
Short-term borrowings					0		$ 0
Unsecured borrowings | Senior Unsecured Notes Due April 5, 2022
Line of Credit Facility [Line Items]
Unsecured offering issued					$ 197,000,000			$ 200,000,000
Interest rate stated percentage								5.125%

Borrowings - Securitizations (D

Borrowings - Securitizations (Details) - USD ($)	Feb. 28, 2017	Oct. 31, 2016	Jul. 31, 2016	May 31, 2016	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Nov. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Securities Financing Transaction [Line Items]
Total Issued					$ 1,900,500,000				$ 1,448,000,000	$ 1,782,000,000
Total loan and accrued interest amount securitized at inception on-balance sheet term securitization					$ 2,101,644,000				$ 1,606,804,000	$ 2,107,042,000
2016-A
Securities Financing Transaction [Line Items]
Total Issued				$ 501,000,000
Weighted Average Life (in years)				4 years 3 days
2016-B
Securities Financing Transaction [Line Items]
Total Issued			$ 607,000,000
Weighted Average Life (in years)			4 years 3 days
2016-C
Securities Financing Transaction [Line Items]
Total Issued		$ 674,000,000
Weighted Average Life (in years)		4 years 3 months 7 days
2017-A
Securities Financing Transaction [Line Items]
Total Issued	$ 772,000,000
Weighted Average Life (in years)	4 years 3 months 7 days
2017-B
Securities Financing Transaction [Line Items]
Total Issued								$ 676,000,000
Weighted Average Life (in years)								4 years 25 days
Basis spread on variable rate								0.80%
2018-A
Securities Financing Transaction [Line Items]
Total Issued							$ 670,000,000
Weighted Average Life (in years)							4 years 5 months 4 days
Basis spread on variable rate						0.78%
2018-B
Securities Financing Transaction [Line Items]
Total Issued						$ 686,500,000
Weighted Average Life (in years)						4 years 4 months 24 days
Basis spread on variable rate					0.76%
2018-C
Securities Financing Transaction [Line Items]
Total Issued					$ 544,000,000
Weighted Average Life (in years)					4 years 3 months 25 days
Basis spread on variable rate					0.77%
LIBOR | 2016-A
Securities Financing Transaction [Line Items]
Basis spread on variable rate				1.38%
LIBOR | 2016-B
Securities Financing Transaction [Line Items]
Basis spread on variable rate			1.36%
LIBOR | 2016-C
Securities Financing Transaction [Line Items]
Basis spread on variable rate		1.15%
LIBOR | 2017-A
Securities Financing Transaction [Line Items]
Basis spread on variable rate	0.93%

Borrowings - Financing VIEs (De

Borrowings - Financing VIEs (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Securities Financing Transaction [Line Items]
Document Period End Date	Sep. 30, 2018
Debt Outstanding
Short Term	$ 0	$ 0
Long Term	4,532,221	3,275,270
Total	4,532,221	3,275,270
Carrying Amount of Assets Securing Debt Outstanding
Restricted Cash	115,658	101,836	$ 66,625
Other Assets	101,000	84,853
Variable Interest Entity, Primary Beneficiary
Debt Outstanding
Short Term	0	0
Long Term	4,335,075	3,078,731
Total	4,335,075	3,078,731
Carrying Amount of Assets Securing Debt Outstanding
Loans	5,174,592	3,691,024
Restricted Cash	111,555	96,983
Other Assets	382,190	240,369
Total	5,668,337	4,028,376
Variable Interest Entity, Primary Beneficiary | Private Education Loan securitization
Debt Outstanding
Short Term	0	0
Long Term	4,335,075	3,078,731
Total	4,335,075	3,078,731
Carrying Amount of Assets Securing Debt Outstanding
Loans	5,174,592	3,691,024
Restricted Cash	111,555	95,966
Other Assets	381,760	240,208
Total	5,667,907	4,027,198
Variable Interest Entity, Primary Beneficiary | ABCP Facility
Debt Outstanding
Short Term	0	0
Long Term	0	0
Total	0	0
Carrying Amount of Assets Securing Debt Outstanding
Loans	0	0
Restricted Cash	0	1,017
Other Assets	430	161
Total	$ 430	$ 1,178

Derivative Financial Instrume_3

Derivative Financial Instruments - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Notional value	$ 7,200,000,000
Net derivatives	33,000,000	$ 20,000,000
Cash collateral held relative to derivative exposure	0	0
Cash collateral pledged	32,000,000	$ 22,000,000
Chicago Mercantile Exchange
Derivative [Line Items]
Notional value	$ 6,600,000,000
Percent of total notional derivative contracts	91.60%
London Clearing House
Derivative [Line Items]
Notional value	$ 600,000,000
Percent of total notional derivative contracts	8.40%

Derivative Financial Instrume_4

Derivative Financial Instruments - Impact of Derivatives on Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Total net derivatives	$ 33,000	$ 20,000
Interest rate swaps
Derivatives, Fair Value [Line Items]
Derivative instruments	1,384	812
Derivative Liabilities	(454)	(2,584)
Total net derivatives	930	(1,772)
Interest rate swaps | Trading
Derivatives, Fair Value [Line Items]
Derivative instruments	78	182
Derivative Liabilities	0	0
Total net derivatives	78	182
Interest rate swaps | Cash Flow | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative instruments	0	0
Derivative Liabilities	(454)	(2,584)
Total net derivatives	(454)	(2,584)
Interest rate swaps | Fair Value | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative instruments	1,306	630
Derivative Liabilities	0	0
Total net derivatives	$ 1,306	$ 630

Derivative Financial Instrume_5

Derivative Financial Instruments - Offsetting Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Other Liabilities
Cash collateral pledged	$ 32,000	$ 22,000
Other Assets
Other Assets
Gross position	1,384	812
Impact of master netting agreement	(340)	(812)
Derivative values with impact of master netting agreements (as carried on balance sheet)	1,044	0
Cash collateral pledged	32,071	0
Net position	33,115	0
Other Liabilities
Other Liabilities
Gross position	(454)	(2,584)
Impact of master netting agreement	340	812
Derivative values with impact of master netting agreements (as carried on balance sheet)	(114)	(1,772)
Cash collateral pledged	0	21,586
Net position	$ (114)	$ 19,814

Derivative Financial Instrume_6

Derivative Financial Instruments - Notional Values (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Notional values	$ 7,200,000
Interest rate swaps
Derivatives, Fair Value [Line Items]
Notional values	7,201,245	$ 5,459,075
Interest rate swaps | Trading
Derivatives, Fair Value [Line Items]
Notional values	1,577,978	987,577
Interest rate swaps | Cash Flow Hedges | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional values	1,312,573	1,408,649
Interest rate swaps | Fair Value Hedges | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional values	$ 4,310,694	$ 3,062,849

Derivative Financial Instrume_7

Derivative Financial Instruments - Schedule of Hedged Items Recorded in Statement of Financial Position (Details) - Deposits - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Carrying Amount of the Hedged Assets/(Liabilities)	$ (4,251,414)	$ (3,036,671)
Cumulative Amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Assets/(Liabilities)	$ 49,694	$ 22,168

Derivative Financial Instrume_8

Derivative Financial Instruments - Impact of Derivatives on Consolidated Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Cash Flow Hedges
Interest expense	$ 140,964	$ 84,163	$ 366,942	$ 217,777
Trading
Total	(1,665)	(188)	(10,882)	(15,016)
Designated as Hedging Instrument
Fair Value Hedges
Hedged items recorded in interest expense	4,809	3,294	27,526	2,673
Derivatives recorded in interest expense	(4,896)	(546)	(27,774)	(7,803)
Trading
Total	(87)	2,748	(248)	(5,130)
Trading
Trading
Change in fair value of future interest payments recorded in earnings	(1,557)	(247)	(8,492)	(1,189)
Total	(1,557)	(247)	(8,492)	(1,189)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent | Reclassification out of Accumulated Other Comprehensive Income | Designated as Hedging Instrument
Cash Flow Hedges
Interest expense	$ (21)	$ (2,689)	$ (2,142)	$ (8,697)

Derivative Financial Instrume_9

Derivative Financial Instruments - Impact of Derivatives on Consolidated Statement of Changes in Stockholders' Equity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Amount of gain recognized in other comprehensive income (loss)	$ 6,453	$ 2,125	$ 34,718	$ (1,133)
Less: amount of loss reclassified in interest expense	(21)	(2,689)	(2,142)	(8,697)
Total change in other comprehensive income (loss) for unrealized gains (losses) on derivatives, before income tax (expense) benefit	$ 6,474	$ 4,814	$ 36,860	$ 7,564

Stockholders' Equity - Common s

Stockholders' Equity - Common stock repurchased (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Equity [Abstract]
Shares repurchased related to employee stock-based compensation plans (in shares)	116,151	81,817	3,056,746	2,666,781
Average purchase price per share (in dollars per share)	$ 11.54	$ 10.93	$ 11.34	$ 12.09
Common shares issued (in shares)	397,004	423,112	6,341,950	5,652,886

Stockholders' Equity - Addition

Stockholders' Equity - Additional Detail (Details)	Sep. 28, 2018$ / shares
Common Stock
Class of Stock [Line Items]
Common stock closing price (in dollars per share)	$ 11.15

Earnings per Common Share (Deta

Earnings per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Numerator:
Net income	$ 103,878	$ 76,371	$ 339,964	$ 241,931
Preferred stock dividends	4,124	3,028	11,441	12,577
Net income attributable to SLM Corporation common stock	$ 99,754	$ 73,343	$ 328,523	$ 229,354
Denominator:
Weighted average shares used to compute basic EPS (in shares)	435,468,000	431,718,000	434,875,000	430,958,000
Effect of dilutive securities:
Dilutive effect of stock options, restricted stock and restricted stock units and Employee Stock Purchase Plan (ESPP) (in shares)	4,551,000	6,701,000	4,609,000	7,464,000
Weighted average shares used to compute diluted EPS (in shares)	440,019,000	438,419,000	439,484,000	438,422,000
Basic earnings per common share attributable to SLM Corporation (in dollars per share)	$ 0.23	$ 0.17	$ 0.76	$ 0.53
Diluted earnings per common share attributable to SLM Corporation (in dollars per share)	$ 0.23	$ 0.17	$ 0.75	$ 0.52
Securities excluded from computation of EPS (in shares)	0	0	0	0

Fair Value Measurements - Valua

Fair Value Measurements - Valuation of Financial Instruments that are Marked-to-Market on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Assets
Available-for-sale investments	$ 172,370	$ 244,088
Fair Value Measurements on a Recurring Basis
Assets
Available-for-sale investments	172,370	244,088
Derivative instruments	1,384	812
Total earning assets	173,754	244,900
Liabilities
Derivative instruments	(454)	(2,584)
Fair Value Measurements on a Recurring Basis | Level 1
Assets
Available-for-sale investments	0	0
Derivative instruments	0	0
Total earning assets	0	0
Liabilities
Derivative instruments	0	0
Fair Value Measurements on a Recurring Basis | Level 2
Assets
Available-for-sale investments	172,370	244,088
Derivative instruments	1,384	812
Total earning assets	173,754	244,900
Liabilities
Derivative instruments	(454)	(2,584)
Fair Value Measurements on a Recurring Basis | Level 3
Assets
Available-for-sale investments	0	0
Derivative instruments	0	0
Total earning assets	0	0
Liabilities
Derivative instruments	$ 0	$ 0

Fair Value Measurements - Fair

Fair Value Measurements - Fair Values of Financial Assets and Liabilities, Including Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Earning assets
Loans held for investment, net, difference	$ 2,188,549	$ 2,105,495
Accrued interest receivable, difference	0
Tax indemnification receivable	54,941	168,011
Total earning assets, difference	2,188,549	2,105,495
Interest-bearing liabilities
Long-term borrowings, difference	28,967	(24,601)
Total interest-bearing liabilities, difference	49,499	(34,688)
Excess of net asset fair value over carrying value	2,238,048	2,070,807
Certificates of deposit
Interest-bearing liabilities
Deposits, difference	20,532	(10,087)
Fair Value
Earning assets
Loans held for investment, net	24,167,452	20,673,136
Cash and cash equivalents	1,839,054	1,534,339
Available-for-sale investments	172,370	244,088
Accrued interest receivable	1,270,026	967,482
Tax indemnification receivable	54,941	168,011
Derivative instruments	1,384	812
Total earning assets	27,505,227	23,587,868
Interest-bearing liabilities
Long-term borrowings	4,503,254	3,299,871
Accrued interest payable	62,627	35,363
Derivative instruments	454	2,584
Total interest-bearing liabilities	22,418,584	18,852,235
Fair Value | Money-market and savings accounts
Interest-bearing liabilities
Deposits	8,923,893	8,470,209
Fair Value | Certificates of deposit
Interest-bearing liabilities
Deposits	8,928,356	7,044,208
Carrying Value
Earning assets
Loans held for investment, net	21,978,903	18,567,641
Cash and cash equivalents	1,839,054	1,534,339
Available-for-sale investments	172,370	244,088
Accrued interest receivable	1,270,026	967,482
Tax indemnification receivable	54,941	168,011
Derivative instruments	1,384	812
Total earning assets	25,316,678	21,482,373
Interest-bearing liabilities
Long-term borrowings	4,532,221	3,275,270
Accrued interest payable	62,627	35,363
Derivative instruments	454	2,584
Total interest-bearing liabilities	22,468,083	18,817,547
Carrying Value | Money-market and savings accounts
Interest-bearing liabilities
Deposits	8,923,893	8,470,209
Deposits, difference	0
Carrying Value | Certificates of deposit
Interest-bearing liabilities
Deposits	$ 8,948,888	$ 7,034,121

Arrangements with Navient Cor_2

Arrangements with Navient Corporation (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2018	Sep. 30, 2017	Apr. 30, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Deferred taxes to be indemnified							$ 283,000
Amount remaining	$ 9,000				$ 9,000
Remaining balance of indemnification receivable in connection with the spin-off	27,000				27,000
Liability for uncertainty in income taxes	26,000				26,000
Adjustment for tax positions relating to historical transactions among entities					120,000
Increase (decrease) in tax indemnification receivable	(90,000)			$ 120,000	(26,991)	$ (44,725)
Adjustment for tax positions expired as a result of federal statute of limitations	90,000
Liability for uncertainty in income taxes relating to historical transactions	20,000				20,000
Gain on sale of portfolio split loans	$ 0		$ 0		$ 2,060	$ 0
Discontinued Operations, Disposed of by Sale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Portfolio split loans sold		$ 43,000
Gain on sale of portfolio split loans		$ 2,000

Regulatory Capital - Well Capit

Regulatory Capital - Well Capitalized Regulatory Requirements (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Actual Amount
Common Equity Tier 1 Capital (to Risk-Weighted Assets)	$ 2,735,622	$ 2,350,081
Tier 1 Capital (to Risk-Weighted Assets)	2,735,622	2,350,081
Total Capital (to Risk-Weighted Assets)	3,032,522	2,597,926
Tier 1 Capital (to Average Assets)	$ 2,735,622	$ 2,350,081
Actual Ratio
Common Equity Tier 1 Capital (to Risk-Weighted Assets)	11.50%	11.90%
Tier 1 Capital (to Risk-Weighted Assets)	11.50%	11.90%
Total Capital (to Risk-Weighted Assets)	12.80%	13.10%
Tier 1 Capital (to Average Assets)	11.10%	11.00%
Well Capitalized Regulatory Requirements, Amount
Common Equity Tier 1 Capital (to Risk-Weighted Assets)	$ 1,541,678	$ 1,288,435
Tier 1 Capital (to Risk-Weighted Assets)	1,897,450	1,585,767
Total Capital (to Risk-Weighted Assets)	2,371,812	1,982,208
Tier 1 Capital (to Average Assets)	$ 1,233,163	$ 1,067,739
Well Capitalized Regulatory Requirements, Ratio
Common Equity Tier 1 Capital (to Risk-Weighted Assets)	6.50%	6.50%
Tier 1 Capital (to Risk-Weighted Assets)	8.00%	8.00%
Total Capital (to Risk-Weighted Assets)	10.00%	10.00%
Tier 1 Capital (to Average Assets)	5.00%	5.00%

Regulatory Capital - Additional

Regulatory Capital - Additional Information (Details) - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Banking and Thrift [Abstract]
Dividends	$ 0	$ 0

Commitments, Contingencies an_2

Commitments, Contingencies and Guarantees (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
Contractual obligation	$ 2,100
Other liabilities reserve	$ 2
Loss contingency, loss emergence period	1 year