SLM (SLM) 10-K 23 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2017	Jan. 31, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	SLM
Entity Registrant Name	SLM CORPORATION
Entity Central Index Key	1,032,033
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)		433,549,312
Entity Public Float			$ 4.9

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents	$ 1,534,339	$ 1,918,793
Available-for-sale investments at fair value (cost of $247,607 and $211,406, respectively)	244,088	208,603
Loans held for investment (net of allowance for losses of $251,475 and $184,701, respectively)	18,567,641	15,137,922
Restricted cash and investments	101,836	53,717
Other interest-earning assets	21,586	49,114
Accrued interest receivable	967,482	766,106
Premises and equipment, net	89,748	87,063
Tax indemnification receivable	168,011	259,532
Other assets	84,853	52,153
Total assets	21,779,584	18,533,003
Liabilities
Deposits	15,505,383	13,435,667
Long-term borrowings	3,275,270	2,167,979
Income taxes payable, net	102,285	184,324
Upromise member accounts	243,080	256,041
Other liabilities	179,310	141,934
Total liabilities	19,305,328	16,185,945
Commitments and contingencies
Preferred stock, par value $0.20 per share, 20 million shares authorized:
Common stock, par value $0.20 per share, 1.125 billion shares authorized: 443.5 million and 436.6 million shares issued, respectively	88,693	87,327
Additional paid-in capital	1,222,277	1,175,564
Accumulated other comprehensive income (loss) (net of tax expense (benefit) of $1,696 and ($5,364), respectively)	2,748	(8,671)
Retained earnings	868,182	595,322
Total SLM Corporation stockholders’ equity before treasury stock	2,581,900	2,414,542
Less: Common stock held in treasury at cost: 11.1 million and 7.7 million shares, respectively	(107,644)	(67,484)
Total equity	2,474,256	2,347,058
Total liabilities and equity	21,779,584	18,533,003
Series A Preferred Stock
Preferred stock, par value $0.20 per share, 20 million shares authorized:
Preferred stock value outstanding	0	165,000
Series B Preferred Stock
Preferred stock, par value $0.20 per share, 20 million shares authorized:
Preferred stock value outstanding	$ 400,000	$ 400,000

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Amortized Cost	$ 247,607	$ 211,406
Loans held for investment	$ 251,475	$ 184,701
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)	443,500,000	436,600,000
Accumulated other comprehensive loss tax benefit	$ 1,696	$ (5,364)
Common stock held in treasury	11,100,000	7,700,000
Series A Preferred Stock
Preferred stock, stated value (in dollars per share)	$ 50	$ 50
Preferred stock, shares issued (in shares)	0	3,300,000
Series B Preferred Stock
Preferred stock, stated value (in dollars per share)	$ 100	$ 100
Preferred stock, shares issued (in shares)	4,000,000	4,000,000

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest income:
Loans	$ 1,413,505	$ 1,060,487	$ 817,120
Investments	8,288	9,160	10,247
Cash and cash equivalents	15,510	7,599	3,751
Total interest income	1,437,303	1,077,246	831,118
Interest expense:
Deposits	223,691	148,408	116,391
Interest expense on short-term borrowings	6,341	7,322	6,490
Interest expense on long-term borrowings	78,050	30,178	5,738
Total interest expense	308,082	185,908	128,619
Net interest income	1,129,221	891,338	702,499
Less: provisions for credit losses	185,765	159,405	90,055
Net interest income after provisions for credit losses	943,456	731,933	612,444
Non-interest income (loss):
Gains on sales of loans, net	0	230	135,358
(Losses) gains on derivatives and hedging activities, net	(8,266)	(958)	5,300
Other income	5,364	69,544	41,935
Total non-interest income (loss)	(2,902)	68,816	182,593
Non-interest expenses:
Compensation and benefits	213,319	183,996	158,975
FDIC assessment fees	28,950	19,209	14,348
Other operating expenses	206,351	182,202	175,772
Total operating expenses	448,620	385,407	349,095
Acquired intangible asset amortization expense	469	906	1,480
Restructuring and other reorganization expenses	0	0	5,398
Total non-interest expenses	449,089	386,313	355,973
Income before income tax expense	491,465	414,436	439,064
Income tax expense	202,531	164,109	164,780
Net income	288,934	250,327	274,284
Preferred stock dividends	15,714	21,204	19,595
Net income attributable to SLM Corporation common stock	$ 273,220	$ 229,123	$ 254,689
Basic earnings per common share attributable to SLM Corporation (in dollars per share)	$ 0.63	$ 0.54	$ 0.60
Average common shares outstanding (in shares)	431,216	427,876	425,574
Diluted earnings per common share attributable to SLM Corporation (in dollars per share)	$ 0.62	$ 0.53	$ 0.59
Average common and common equivalent shares outstanding (in shares)	438,551	432,919	432,234

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 288,934	$ 250,327	$ 274,284
Other comprehensive income (loss):
Unrealized losses on investments	(716)	(1,792)	(2,205)
Unrealized gains (losses) on cash flow hedges	19,195	13,764	(5,224)
Total unrealized gains (losses)	18,479	11,972	(7,429)
Income tax (expense) benefit	(7,060)	(4,584)	2,763
Other comprehensive income (losses), net of tax (expense) benefit	11,419	7,388	(4,666)
Total comprehensive income	$ 300,353	$ 257,715	$ 269,618

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands	Total	Total SLM Corporation Equity	Preferred Stock	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Series A Preferred StockTotal SLM Corporation Equity	Series A Preferred StockPreferred Stock	Series A Preferred StockRetained Earnings	Series B Preferred StockTotal SLM Corporation Equity	Series B Preferred StockRetained Earnings
Beginning balance, shares issued (in shares) at Dec. 31, 2014			7,300,000	424,804,125
Beginning balance (in shares) at Dec. 31, 2014				423,438,848	(1,365,277)
Beginning balance at Dec. 31, 2014		$ 1,829,958	$ 565,000	$ 84,961	$ (12,187)	$ 1,090,511	$ (11,393)	$ 113,066
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 274,284	274,284						274,284
Other comprehensive income (loss), net of tax	(4,666)	(4,666)					(4,666)
Total comprehensive income	$ 269,618	269,618
Separation adjustments related to Spin-Off of Navient Corporation		1,660				1,660
Cash dividends:
Preferred stock									$ (11,501)		$ (11,501)	$ (8,094)	$ (8,094)
Redemption of Series A Preferred Stock (in shares)	(3,008,913)
Dividend equivalent units related to employee stock-based compensation plans		0				1,146		(1,146)
Issuance of common shares (in shares)	5,873,309			5,873,309
Issuance of common shares		15,980		$ 1,175		14,805
Tax benefit (deficiency) related to employee stock-based compensation		6,140				6,140
Stock-based compensation expense		21,598				21,598
Shares repurchased related to employee stock-based compensation plans (in shares)				(3,008,913)	(3,008,913)
Shares repurchased related to employee stock-based compensation plans		(29,036)			$ (29,036)
Ending balance, shares issued (in shares) at Dec. 31, 2015			7,300,000	430,677,434
Ending balance (in shares) at Dec. 31, 2015				426,303,244	(4,374,190)
Ending balance at Dec. 31, 2015		2,096,323	$ 565,000	$ 86,136	$ (41,223)	1,135,860	(16,059)	366,609
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 250,327	250,327						250,327
Other comprehensive income (loss), net of tax	7,388	7,388					7,388
Total comprehensive income	$ 257,715	257,715
Cash dividends:
Preferred stock									(11,501)		(11,501)	(9,703)	(9,703)
Redemption of Series A Preferred Stock (in shares)	(3,354,730)
Dividend equivalent units related to employee stock-based compensation plans		0				410		(410)
Issuance of common shares (in shares)	5,955,045			5,955,045
Issuance of common shares		19,191		$ 1,191		18,000
Tax benefit (deficiency) related to employee stock-based compensation		(1,650)				(1,650)
Stock-based compensation expense		22,944				22,944
Shares repurchased related to employee stock-based compensation plans (in shares)				(3,354,730)	(3,354,730)
Shares repurchased related to employee stock-based compensation plans		(26,261)			$ (26,261)
Ending balance, shares issued (in shares) at Dec. 31, 2016			7,300,000	436,632,479
Ending balance (in shares) at Dec. 31, 2016				428,903,559	(7,728,920)
Ending balance at Dec. 31, 2016	$ 2,347,058	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	288,934	288,934						288,934
Other comprehensive income (loss), net of tax	11,419	11,419					11,419
Total comprehensive income	$ 300,353	300,353
Cumulative effect of the new stock compensation standard		165				429		(264)
Cash dividends:
Preferred stock									$ (3,961)		$ (3,961)	$ (11,753)	$ (11,753)
Redemption of Series A Preferred Stock (in shares)	(3,358,417)									(3,300,000)
Redemption of Series A Preferred Stock		(165,000)								$ (165,000)
Dividend equivalent units related to employee stock-based compensation plans		0				96		(96)
Issuance of common shares (in shares)	6,831,108			6,831,108
Issuance of common shares		19,655		$ 1,366		18,289
Stock-based compensation expense		27,899				27,899
Shares repurchased related to employee stock-based compensation plans (in shares)				(3,358,417)	(3,358,417)
Shares repurchased related to employee stock-based compensation plans		(40,160)			$ (40,160)
Ending balance, shares issued (in shares) at Dec. 31, 2017			4,000,000	443,463,587
Ending balance (in shares) at Dec. 31, 2017				432,376,250	(11,087,337)
Ending balance at Dec. 31, 2017	$ 2,474,256	$ 2,474,256	$ 400,000	$ 88,693	$ (107,644)	$ 1,222,277	$ 2,748	$ 868,182

CONSOLIDATED STATEMENTS OF CHA7

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Series A Preferred Stock
Preferred stock dividend rate (in dollars per share)	$ 1.74	$ 3.49	$ 3.48
Series B Preferred Stock
Preferred stock dividend rate (in dollars per share)	$ 2.91	$ 2.41	$ 2.06

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net income	$ 288,934	$ 250,327	$ 274,284
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Provisions for credit losses	185,765	159,405	90,055
Deferred tax benefit	(58,752)	(88,732)	(77,227)
Amortization of brokered deposit placement fee	9,372	10,133	10,510
Amortization of ABCP Facility upfront fee	1,316	1,229	2,337
Amortization of deferred loan origination costs and fees, net	8,258	5,811	3,746
Net amortization of discount on investments	2,082	2,043	1,716
Loss (income) on tax indemnification receivable	31,888	(12,283)	(5,398)
Depreciation of premises and equipment	11,171	9,592	7,437
Amortization of acquired intangibles	469	906	1,480
Stock-based compensation expense	27,899	22,944	21,598
Unrealized losses (gains) on derivative and hedging activities, net	7,248	2,263	(2,500)
Gains on sale of loans, net	0	(230)	(135,358)
Other adjustments to net income, net	5,836	3,524	(306)
Changes in operating assets and liabilities:
Net decrease in loans held for sale	0	0	55
Origination of loans held for sale	0	0	(55)
Increase in accrued interest receivable	(703,081)	(582,361)	(377,648)
Decrease (increase) in restricted cash and investments, net	4,247	(3,559)	(737)
Decrease in other interest-earning assets	27,528	5,731	17,634
Decrease in tax indemnification receivable	59,633	59,633	59,633
Increase in other assets	(72,920)	(47,162)	(18,070)
(Decrease) increase in income tax payable, net	(19,687)	(20,647)	62,953
Increase in accrued interest payable	14,304	3,736	303
(Decrease) increase in payable due to entity that is a subsidiary of Navient	(593)	553	(6,774)
Increase (decrease) in other liabilities	2,171	14,562	(14,731)
Total adjustments	(455,846)	(452,909)	(359,347)
Total net cash used in operating activities	(166,912)	(202,582)	(85,063)
Investing activities
Loans acquired and originated	(5,243,732)	(4,698,548)	(4,366,651)
Net proceeds from sales of loans held for investment	6,992	9,521	1,547,373
Proceeds from claim payments	49,146	64,869	111,580
Net decrease in loans held for investment	2,065,727	1,332,341	913,005
Increase in restricted cash and investment - variable interest entities	(52,366)	(22,178)	(22,439)
Purchases of available-for-sale securities	(78,327)	(55,767)	(64,112)
Proceeds from sales and maturities of available-for-sale securities	40,044	38,721	33,735
Total net cash used in investing activities	(3,212,516)	(3,331,041)	(1,847,509)
Financing activities
Brokered deposit placement fee	(12,200)	(4,371)	(4,098)
Net increase (decrease) increase in certificates of deposit	1,579,615	(434,740)	611,643
Net increase in other deposits	508,389	2,412,221	324,518
Issuance costs for collateralized borrowings	0	(2,090)	0
Borrowings collateralized by loans in securitization trusts - issued	1,440,127	1,775,692	620,681
Borrowings collateralized by loans in securitization - repaid	(534,905)	(187,686)	(41,976)
Borrowings under ABCP Facility	300,000	376,325	1,210,180
Issuance costs for unsecured debt offering	(1,057)	0	0
Repayment of borrowings under ABCP Facility	(300,000)	(876,500)	(710,005)
Fees paid - ABCP Facility	(1,281)	(1,450)	(2,337)
Unsecured debt issued	197,000	0	0
Redemption of Series A Preferred Stock	(165,000)	0	0
Preferred stock dividends paid	(15,714)	(21,204)	(19,595)
Net cash provided by (used in) financing activities	2,994,974	3,036,197	1,989,011
Net (decrease) increase in cash and cash equivalents	(384,454)	(497,426)	56,439
Cash and cash equivalents at beginning of year	1,918,793	2,416,219	2,359,780
Cash and cash equivalents at end of year	1,534,339	1,918,793	2,416,219
Cash disbursements made for:
Interest	269,017	169,854	111,563
Income taxes paid	282,278	271,721	205,698
Income taxes refunded	$ (1,401)	$ (86)	$ (25,151)

Organization and Business

Organization and Business	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Business	Organization and Business SLM Corporation (“Sallie Mae,” “SLM,” the “Company,” “we” “our” or “us”) is a holding company that operates through a number of subsidiaries. Its predecessor was formed in 1972 as the Student Loan Marketing Association, a federally-chartered government-sponsored enterprise (the “GSE”), with the goal of furthering access to higher education by providing liquidity to the education loan marketplace. The GSE’s federal charter prohibited it from originating student loans in the primary market. In 1996, the United States Congress passed the Student Loan Marketing Association Reorganization Act, which set the stage for the “privatization” of the GSE. As part of the privatization process, we incorporated SLM Corporation in 1997 as a Delaware corporation, the GSE became a subsidiary of SLM Corporation, and by mid-2004 the GSE stopped purchasing loans insured or guaranteed under the Federal Family Education Loan Program (“FFELP Loans”) in the secondary market and was dissolved by the end of 2004. On November 3, 2005, SLM Corporation formed Sallie Mae Bank, a Utah industrial bank subsidiary (the “Bank”), to fund and originate Private Education Loans on behalf of SLM Corporation. While the Bank first originated Private Education Loans in February 2006, SLM Corporation continued to purchase a portion of its Private Education Loans (hereinafter defined) from its third-party lending partners through mid-2009. With some minor exceptions, the Bank became the sole originator of Private Education Loans for SLM Corporation beginning with the 2009-2010 academic year, the first academic year following the launch of the Bank’s Smart Option Student Loan program in mid-2009. On April 30, 2014, we completed our plan to legally separate into two distinct publicly-traded entities: an education loan management, servicing and asset recovery business, named Navient Corporation (“Navient”), which retained all assets and liabilities generated prior to the Spin-Off (hereinafter defined) other than those explicitly retained by SLM Corporation; and a consumer banking business, named SLM Corporation. The separation of Navient from SLM Corporation (the “Spin-Off”) was preceded by an internal corporate reorganization, which was the first step to separate the education loan management, servicing and asset recovery business from the consumer banking business. As a result of a holding company merger under Section 251(g) of the Delaware General Corporation Law, which is referred to herein as the “SLM Merger,” all of the shares of then existing SLM Corporation’s common stock were converted, on a 1 -to-1 basis, into shares of common stock of New BLC Corporation, a newly formed company that was a subsidiary of pre-Spin-Off SLM Corporation (“pre-Spin-Off SLM”), and, pursuant to the SLM Merger, New BLC Corporation replaced then existing SLM Corporation as the publicly-traded registrant and changed its name to SLM Corporation. As part of the internal corporate reorganization, the assets and liabilities associated with the education loan management, servicing and asset recovery business were transferred to Navient, and those assets and liabilities associated with the consumer banking business remained with or were transferred to the newly-constituted SLM Corporation. The separation and distribution were accounted for on a substantially tax-free basis. Our primary business is to originate and service loans we make to students and their families to finance the cost of their education. 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 FFELP Loans. The core of our marketing strategy is to generate Private Education Loan originations by promoting our products on campuses through the financial aid offices as well as through online and direct marketing to students and their families. The Bank is regulated by the Utah Department of Financial Institutions (the “UDFI”), the Federal Deposit Insurance Corporation (the “FDIC”) and the Consumer Financial Protection Bureau (the “CFPB”). We also operate Upromise, Inc. (“Upromise”), a save-for-college rewards program helping Americans save for higher education.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies Use of Estimates and Assumptions The financial reporting and accounting policies of SLM Corporation conform to generally accepted accounting principles in the United States of America (“GAAP”). The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Key accounting policies that include significant judgments and estimates include the valuation of allowance for loan losses, fair value measurements and derivative accounting. Consolidation 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. 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. Cash and Cash Equivalents Cash and cash equivalents include cash held in the Federal Reserve Bank of San Francisco (the “FRB”) and commercial bank accounts, and other short-term liquid instruments with original maturities of three months or less. Fees associated with investing cash and cash equivalents are amortized into interest income using the effective interest rate method. Investments Investments consisted of mortgage-backed securities and Utah Housing Corporation bonds. We record our investment purchases and sales on a trade date basis. The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts, which are amortized using the effective interest rate method. Our investments are classified as available-for-sale and reported at fair value. Unrealized gains or losses on available-for-sale investments are recorded in equity and are reported as a component of other comprehensive income (loss), net of applicable income taxes, unless a decline in the investment’s value is considered to be other-than-temporary, in which case the loss is recorded directly to earnings. Management reviews all investments at least quarterly to determine whether any impairment is other-than-temporary. Impairment is evaluated by considering several factors, including the length of time and extent to which the fair value has been less than cost, the financial condition and near-term prospects of the issuer, and the intent and ability to retain the investment to allow for an anticipated recovery in fair value. If, based on the analysis, it is determined that the impairment is other-than-temporary, the investment is written down to fair value and a loss is recognized through earnings. Loans Held for Investment Loans, consisting primarily of Private Education Loans and FFELP Loans, that we have the ability and intent to hold for the foreseeable future are classified as held for investment, and are carried at amortized cost. Amortized cost includes the unamortized premiums, discounts, and capitalized origination costs and fees, all of which are amortized to interest income as discussed under “Loan Interest Income.” Loans which are held for investment are reported net of an allowance for loan losses. Restricted Cash and Investments Restricted cash and investments primarily include amounts held in student loan securitization trusts and other secured borrowings. This cash must be used to make payments related to trust obligations. Amounts on deposit in these accounts are primarily the result of timing differences between when principal and interest is collected on the trust assets and when principal and interest is paid on trust liabilities. Allowance for Loan Losses We maintain an allowance for loan losses at an amount sufficient to absorb probable losses incurred in our portfolios, as well as regarding future loan commitments, at the reporting date based on a projection of estimated probable credit losses incurred in the portfolio. We consider a loan to be impaired when, based on current information, a loss has been incurred and it is probable that we will not receive all contractual amounts due. When making our assessment as to whether a loan is impaired, we also take into account more than insignificant delays in payment. We generally evaluate impaired loans on an aggregate basis by grouping similar loans. We analyze our portfolios to determine the effects that the various stages of delinquency and forbearance have on borrower default behavior and ultimate charge off. We estimate the allowance for loan losses for our loan portfolios using a roll rate analysis of delinquent and current accounts. A “roll rate analysis” is a technique used to estimate the likelihood that a loan receivable may progress through the various delinquency stages and ultimately charge off. We also take into account the current and future economic environment and certain other qualitative factors when calculating the allowance for loan losses. The evaluation of the allowance for loan losses is inherently subjective, as it requires material estimates that may be susceptible to significant changes. Our default estimates are based on a loss emergence period of one year for Private Education Loans and two years for FFELP Loans. A loss emergence period represents the expected period between the first occurrence of an event likely to cause a loss on a loan and the date the loan is expected to be charged off, taking into consideration account management practices that affect the timing of a loss, such as the usage of forbearance. The loss emergence period underlying the allowance for loan losses is subject to a number of assumptions. If actual future performance in delinquency, charge-offs and recoveries is significantly different than estimated, or account management assumptions or practices were to change, this could materially affect the estimate of the allowance for loan losses, the timing of when losses are recognized, and the related provision for credit losses on our consolidated statements of income. We utilize various models to determine an appropriate allowance for loan losses. Changes to model inputs are made as deemed necessary. These models are reviewed and validated periodically. Below we describe in further detail our policies and procedures for the allowance for loan losses as they relate to our Private Education Loan, Personal Loan, and FFELP Loan portfolios. Allowance for Private Education Loan Losses We maintain an allowance for loan losses at an amount sufficient to absorb probable losses incurred in our portfolios at the reporting date based on a projection of estimated probable credit losses incurred in the portfolio. In determining the allowance for loan losses on our Private Education Loans that are not troubled debt restructurings (“TDRs”), we estimate the principal amount of loans that will default over the next year ( one year being the expected period between a loss event and default) using a roll rate model and how much we expect to recover over the same one -year period related to the defaulted amount. The expected defaults less our expected recoveries adjusted for any qualitative factors (discussed below) equal the allowance related to this portfolio. Our historical experience indicates that, on average, the time between the date that a customer experiences a default causing event (i.e., the loss trigger event) and the date that we charge off the unrecoverable portion of that loan is one year. In estimating both the non-TDR and TDR allowance amounts, we start with historical experience of customer delinquency and default behavior. We make judgments about which historical period to start with and then make further judgments about whether that historical experience is representative of future expectations and whether additional adjustments may be needed to those historical default rates. We also take certain other qualitative factors into consideration when calculating the allowance for loan losses. These qualitative factors include, but are not limited to, changes in the economic environment, changes in lending policies and procedures, including changes in underwriting standards and collection, charge-off and recovery practices not already included in the analysis, and the effect of other external factors such as legal and regulatory requirements on the level of estimated credit losses. Our non-TDR allowance for loan losses is estimated using an analysis of delinquent and current accounts. Our roll rate model is used to estimate the likelihood that a loan receivable may progress through the various delinquency stages and ultimately charge off. Once a charge-off forecast is estimated, a recovery assumption is layered on top. In estimating recoveries, we use both estimates of what we would receive from the sale of defaulted loans as well as historical borrower payment behavior to estimate the timing and amount of future recoveries on charged-off loans. The roll rate analysis model is based upon actual experience using the 120 day charge-off default aversion strategies. Once the quantitative calculation is performed, we review the adequacy of the allowance for loan losses and determine if qualitative adjustments need to be considered. In the fourth quarter of 2015, we stopped our previous practice of selling all defaulted loans to third-parties and began collecting on some defaulted loans in-house. It is our expectation that in the future we will continue to collect on defaulted loans in-house as well as sell defaulted loans to third-parties. Prior to this change in practice, we only used estimates of what we would receive from the sale of delinquent loans in estimating recoveries. For December 31, 2017 and 2016, we used both an estimate of recovery rates from in-house collections as well as expectations of future sales of defaulted loans to estimate the timing and amount of future recoveries on charged-off loans. In connection with the Spin-Off, the agreement under which the Bank previously made sales of defaulted loans to an affiliate was amended so that the Bank now has the right to require Navient to purchase (at fair value) loans only where (a) the borrower has a lending relationship with both the Bank and Navient (“Split Loans”) and (b) 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. At December 31, 2017, we held approximately $48 million of Split Loans. Allowance for Personal Loans In December 2016, we began to acquire newly-originated personal loans (“Personal Loans”). We maintain an allowance for loan losses at an amount sufficient to absorb probable losses incurred in this portfolio at the reporting date based on a projection of estimated probable credit losses incurred in the portfolio. In determining the allowance for loan losses on our Personal Loan portfolio that are not TDRs, we estimate the principal amount of the loans that will default over the next twelve months (twelve months being the expected period between a loss event and default) and how much we expect to recover over the same twelve-month period related to the defaulted amounts. The expected defaults less our expected recoveries adjusted for any qualitative factors equal the allowance related to this portfolio. At December 31, 2017, and 2016, we held $ 393.7 million and $ 12.8 million, respectively, in Personal Loans, net of allowance. At December 31, 2017, there were no Personal Loans classified as TDRs. Troubled Debt Restructurings Separately, for our TDR portfolio, we estimate an allowance amount sufficient to cover life-of-loan expected losses through an impairment calculation based on the difference between the loan’s basis and the present value of expected future cash flows (which would include life-of-loan default and recovery assumptions) discounted at the loan’s original effective interest rate. Our TDR portfolio is comprised mostly of loans with interest rate reductions and loans with forbearance usage greater than three months , as further described below. We modify the terms of loans for certain borrowers when we believe such modifications may increase the ability and willingness of a borrower to make payments and thus increase the ultimate overall amount collected on a loan. These modifications generally take the form of a forbearance, a temporary interest rate reduction or an extended repayment plan. Until the fourth quarter of 2017, we generally considered a loan that was in full principal and interest repayment status which had received more than three months of forbearance in a 24 -month period to be a TDR; however, during the first nine months after a loan had entered full principal and interest repayment status, we did not count up to the first six months of forbearance received during that period against the three-month policy limit. Beginning in the fourth quarter of 2017, we revised the policy described above for identifying when a loan should be classified as a TDR due to forbearance. Historically, all loans receiving forbearance under the thresholds described above were classified as TDRs. However, with the refinement, those loans with a FICO score above a certain threshold (based on the most recent quarterly FICO score refresh) that are granted a forbearance will not be classified as TDRs, while loans with a FICO score under the threshold (based on the most recent quarterly FICO score refresh) that are granted a forbearance will be classified as TDRs, once they reach our policy limit for forbearances described above (i.e., more than three months in a 24-month period, subject to the exceptions described for the first nine months after a loan enters full principal and interest repayment status).This change in our determination of when loans should be classified as TDRs does not affect any of our existing loans classified as TDRs and it does not change any of the existing thresholds regarding length of forbearance for becoming a TDR. Instead, it is an additional filter in the TDR analysis that is applied after the loan has met the requisite number of months in forbearance. This change was adopted prospectively beginning in the fourth quarter of 2017 and had an immaterial effect on the allowance for loan losses and provision for loan losses. A loan also becomes a TDR when it is modified to reduce the interest rate on the loan (regardless of when such modification occurs and/or whether such interest rate reduction is temporary). 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. Once a loan qualifies for TDR status, it remains a TDR for allowance purposes for the remainder of its life. As of December 31, 2017 and 2016, approximately 66 percent and 69 percent, respectively, of TDRs were classified as such due to their forbearance status. Key Credit Quality Indicators We determine the collectability of our Private Education Loan portfolio by evaluating certain risk characteristics. We consider credit score, existence of a cosigner, loan status and loan seasoning as the key credit quality indicators because they have the most significant effect on the determination of the adequacy of our allowance for loan losses. Credit scores are an indicator of the creditworthiness of borrowers and the higher the credit scores the more likely it is the borrowers will be able to make all of their contractual payments. Loan status affects the credit risk because a past due loan is more likely to result in a credit loss than a current loan. Additionally, loans in the deferred payment status have different credit risk profiles compared with those in current pay status. Loan seasoning affects credit risk because a loan with a history of making payments generally has a lower incidence of default than a loan with a history of making infrequent or no payments. The existence of a cosigner lowers the likelihood of default as well. We monitor and update these credit quality indicators in the analysis of the adequacy of our allowance for loan losses on a quarterly basis. For Personal Loans, we consider FICO scores at origination and seasoning to be our key credit quality indicators for the same reasons discussed above. Certain Private Education Loans do not require borrowers to begin repayment until six months after they have graduated or otherwise left school. Consequently, the loss estimates for these loans is generally low while the borrower is in school. At December 31, 2017 and 2016, 27 percent and 29 percent , respectively, of the principal balance in the Private Education Loan portfolio was related to borrowers who are in an in-school (fully deferred), grace, or deferment status and not required to make payments. As this population of borrowers leaves school, they will be required to begin payments on their loans, and the allowance for losses may change accordingly. Similar to the rules governing FFELP payment requirements, our collection policies allow for periods of nonpayment for borrowers requesting additional payment grace periods upon leaving school or experiencing temporary difficulty meeting payment obligations. This is referred to as forbearance status and is considered separately in the allowance for loan losses. The loss emergence period is in alignment with the typical collection cycle and takes into account these periods of nonpayment. As part of concluding on the adequacy of the allowance for loan losses, we review key allowance and loan metrics. The most relevant of these metrics considered are the allowance coverage of net charge-offs ratio; the allowance as a percentage of ending total loans and of ending loans in repayment; and delinquency and forbearance percentages. We consider a loan to be delinquent 31 days after the last payment was contractually due. We use a model to estimate the amount of uncollectible accrued interest on Private Education Loans and reserve for that amount against current period interest income. Allowance for FFELP Loan Losses 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 default claims. For loans disbursed after October 1, 1993, and before July 1, 2006, we receive 98 percent reimbursement. For loans disbursed prior to October 1, 1993, we receive 100 percent reimbursement. The allowance for FFELP Loan losses uses historical experience of customer default behavior and a two -year loss emergence period to estimate the credit losses incurred in the loan portfolio at the reporting date. We apply the default rate projections, net of applicable risk sharing, to each category for the current period to perform our quantitative calculation. Once the quantitative calculation is performed, we review the adequacy of the allowance for loan losses and determine if qualitative adjustments need to be considered. Deposits Our retail deposit accounts are principally certificates of deposit (“CDs”), money market deposit accounts (“MMDAs”) and high-yield savings (“HYS”) accounts. CDs are accounts that have a stipulated maturity and interest rate. Retail CDs may be withdrawn early, but a penalty is assessed. MMDA and HYS accounts are both interest and non-interest bearing accounts that have no maturity or expiration date. For retail MMDA and HYS accounts, the depositor may be required to give written notice of any intended withdrawal not less than seven days before the withdrawal is made, although this provision is not generally enforced. The Bank also includes brokered CDs in its funding base. Early withdrawal of brokered CDs is prohibited (except in the case of death or legal incapacity). Other deposit accounts include large interest-bearing omnibus accounts deposited in the Bank by commercial entities having custodial responsibilities for many underlying accounts. These omnibus accounts may be structured with or without fixed maturities, and may have fixed or variable interest rates. Upromise member accounts Upromise member accounts represent amounts owed to Upromise rewards members for rebates they have earned from qualifying purchases from Upromise’s participating merchants. These amounts are held in trust for the benefit of the members until distributed in accordance with the Upromise member’s request and/or the terms of the Upromise service agreement. Upromise, which acts as the trustee for the trust, has deposited a majority of the cash with the Bank pursuant to a money market deposit account agreement between the Bank and Upromise as trustee of the trust. Fair Value Measurement We use estimates of fair value in applying various accounting standards for our financial statements. Fair value measurements are used in one of four ways: • In the consolidated balance sheet with changes in fair value recorded in the consolidated statement of income; • In the consolidated balance sheet with changes in fair value recorded in the accumulated other comprehensive income section of the consolidated statement of changes in equity; • In the consolidated balance sheet for instruments carried at lower of cost or fair value with impairment charges recorded in the consolidated statement of income; and • In the notes to the consolidated financial statements. Fair value is defined as the price to sell an asset or transfer a liability in an orderly transaction between willing and able market participants. In general, our policy in estimating fair value is to first look at observable market prices for identical assets and liabilities in active markets, where available. When these are not available, other inputs are used to model fair value such as prices of similar instruments, yield curves, volatilities, prepayment speeds, default rates and credit spreads (including for our liabilities), relying first on observable data from active markets. Depending on current market conditions, additional adjustments to fair value may be based on factors such as liquidity, credit, and bid/offer spreads. Transaction costs are not included in the determination of fair value. When possible, we seek to validate the model’s output to market transactions. Depending on the availability of observable inputs and prices, different valuation models could produce materially different fair value estimates. The values presented may not represent future fair values and may not be realizable. 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. Classification is based on the lowest level of input that is significant to the fair value of the instrument. The three levels are as follows: • Level 1 — Quoted prices (unadjusted) in active markets for identical assets or liabilities that we have the ability to access at the measurement date. The types of financial instruments included in level 1 are highly liquid instruments with quoted prices. • Level 2 — Inputs from active markets, other than quoted prices for identical instruments, are used to determine fair value. Significant inputs are directly observable from active markets for substantially the full term of the asset or liability being valued. • Level 3 — Pricing inputs significant to the valuation are unobservable. Inputs are developed based on the best information available. However, significant judgment is required by us in developing the inputs. Loan Interest Income For all loans, including impaired loans, classified as “held for investment,” we recognize interest income as earned, adjusted for the amortization of deferred direct origination and acquisition costs. This adjustment is recognized based upon the expected yield of the loan over its life after giving effect to prepayments and extensions. We consider our constant prepayment rate (“CPR”) estimates a significant accounting assumption used to measure the expected prepayment activity in our education loan portfolio. The estimates are based on a number of factors such as historical prepayment rates for loans with similar loan characteristics, assumptions about portfolio composition and loan terms, and the prepayment curve’s tendency to follow a ramp pattern (i.e., the prepayment rate typically increases during the in-school and early repayment periods, then stabilizes). The CPR measures the expected prepayment activity over the life of the loan and is applied as a flat-rate input assumption when used in forecasting. Additionally, interest earned on education loans reflects potential non-payment adjustments in accordance with our uncollectible interest recognition policy as discussed further in “Allowance for Loan Losses” of this Note 2. Because of this, we do not place loans in nonaccrual status prior to charge-off. We do not amortize any adjustments to the basis of education loans when they are classified as held-for-sale. Our CPR estimates include the effect of voluntary prepayments and consolidation (if the loans are consolidated to third parties), both of which shorten the lives of loans. CPR estimates also consider the utilization of deferment, forbearance, and extended repayment plans, which lengthen the lives of loans. We regularly evaluate the assumptions used to estimate the CPRs. In instances where there are changes to the assumptions, amortization of deferred direct origination and acquisition costs is adjusted on a cumulative basis to reflect the change since the origination or purchase of the loan. For the year ended December 31, 2017, our CPR for Private Education Loans was 5.94 percent , compared with a CPR of 5.00 percent for the year ended December 31, 2016. We also pay to the U.S. Department of Education (the “DOE”) an annual 105 basis point Consolidation Loan Rebate Fee on FFELP consolidation loans, which is netted against loan interest income. Additionally, interest earned on education loans reflects potential non-payment adjustments in accordance with our uncollectible interest recognition policy. We do not amortize any adjustments to the basis of education loans when they are classified as “held-for-sale.” We recognize certain fee income (primarily late fees) on education loans when earned according to the contractual provisions of the promissory notes, as well as our expectation of collectability. Fee income is recorded when earned in “other non-interest income” in the accompanying consolidated statements of income. Interest Expense Interest expense is based upon contractual interest rates adjusted for the amortization of issuance costs. We incur interest expense on interest bearing deposits comprised of non-maturity savings deposits, brokered and retail CDs, and brokered and retail MMDAs, as well as on unsecured and secured financings. Interest expense is recognized when amounts are contractually due to deposit and debt holders and is adjusted for net payments/receipts related to interest rate swap agreements that qualify and are designated hedges of interest bearing liabilities. Interest expense also includes the amortization of deferred gains and losses on closed hedge transactions that qualified as hedges. Amortization of debt issuance costs, premiums, discounts and terminated hedge-basis adjustments are recognized using the effective interest rate method. We incur certain fees related to our Private Education Loan asset-backed commercial paper facility (the “ABCP Facility”), including an unused ABCP Facility fee, and also incur fees related to our term asset-backed securities (“ABS”). These fees are included in interest expense. Refer to Note 8, “Deposits,” and Note 9, “Borrowings” for further details of our interest bearing liabilities. Gains on Sale of Loans, Net We may participate and sell loans to third-parties and affiliates, including entities that were related parties prior to the Spin-Off. These sales may occur through whole loan sales or securitization transactions that qualify for sales treatment. If a transfer of loans qualifies as a sale, we derecognize the loan and recognize a gain or loss as the difference between the carry basis of the loan sold and liabilities retained and the compensation received. We recognize the results of a transfer of loans based upon the settlement date of the transaction. These loans were initially recorded as held for investment, and were transferred to held-for-sale immediately prior to sale or securitization. We did not sell loans in 2017 and 2016. Prior to the Spin-Off, the Bank sold loans to an entity that is now a subsidiary of Navient when loans became 90 days delinquent and to facilitate securitization transactions. Subsequent to the Spin-Off, we sold loans through loan sales and securitization transactions with third-parties (including Navient) resulting in a net gain on sale of loans of $ 135 million for the year ended December 31, 2015. See Note 16, “Arrangements with Navient Corporation,” for further discussion regarding loan purchase agreements. Other Income Our Upromise subsidiary has a number of programs that encourage consumers to save for the cost of college education. We have established a consumer savings network, which is designed to promote college savings by consumers who are members of this program by encouraging them to purchase goods and services from the merchants that participate in the program. Participating merchants generally pay Upromise fees based on member purchase volume, either online or in stores, depending on the contractual arrangement with the merchant. We recognize revenue as marketing and administrative services are rendered, based upon contractually determined rates and member purchase volumes. Also included in other income are late fees on both Private Education Loans and FFELP Loans, which we recognize when the cash has been received, fees related to our credit card affinity program, income for servicing private student loans for third-parties and changes to our tax indemnification receivable from Navient. Securitization Accounting Our securitizations transactions use a two-step structure with a special purpose entity VIE that legally isolates the transferred assets from us in the event of bankruptcy or receivership. Transactions receiving sale treatment are also structured to ensure that the holders of the beneficial interests issued are not constrained from pledging or exchanging their interests, and that we do not maintain effective control over the transferred assets. If these criteria are not met, then the transaction is accounted for as an on-balance sheet secured borrowing. If a securitization qualifies as a sale, we then assess whether we are the primary beneficiary of the securitization trust and are required to consolidate such trust. We are considered the primary beneficiary if we have 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. There can be considerable judgment as it relates to determining the primary beneficiary of the VIEs. There are no “bright line” tests. Rather, the assessment of who has the power to direct the activities of the VIE that most significantly affect the VIE’s economic performance and who has the obligation to absorb losses or receive benefits of the entity that could potentially be significant to the VIE can be very qualitative and judgmental in nature. If we are the primary beneficiary, then no gain or loss is recognized. We have determined that as the servicer of Sallie Mae securitization trusts, we meet the first primary beneficiary criterion because we have the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance. Irrespective of whether a securitizati

Cash and Cash Equivalents

Cash and Cash Equivalents	12 Months Ended
	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Cash and Cash Equivalents	Cash and Cash Equivalents As of December 31, 2017 , cash and cash equivalents include cash due from the FRB of $ 1.5 billion and cash due from depository institutions of $43.1 million. As of December 31, 2016 , cash and cash equivalents include cash due from the FRB of $1.9 billion and cash due from depository institutions of $ 26.9 million. As of December 31, 2017 and 2016 , we had no outstanding cash equivalents. In 2010, the FRB introduced the Term Deposit Facility to facilitate the conduct of monetary policy by providing a tool that may be used to manage the aggregate quantity of reserve balances held by depository institutions. Under this program, the FRB accepts deposits for a stated maturity at a rate of interest determined via auction. The funds are removed from the accounts of participating institutions for the life of the term deposit. We participated in these auctions in 2017 and 2016 , resulting in interest income of $0.5 million and $0.2 million, respectively. As of December 31, 2017 and 2016 , no funds were on deposit with the FRB under this program. We maintain average reserve balances with the FRB based on a percentage of deposits. The average amounts of those reserves for the years ended December 31, 2017 and 2016 were $0 and $0.5 million, respectively.

Investments

Investments	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Investments	Investments The amortized cost and fair value of securities available for sale are as follows: 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 December 31, 2016 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Available for sale: Mortgage-backed securities $ 196,406 $ 929 $ (3,042 ) $ 194,293 Utah Housing Corporation bonds 15,000 — (690 ) 14,310 Total $ 211,406 $ 929 $ (3,732 ) $ 208,603 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 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 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 As of December 31, 2016: Mortgage-backed securities $ (2,423 ) $ 129,549 $ (619 ) $ 10,885 $ (3,042 ) $ 140,434 Utah Housing Corporation bonds (690 ) 14,310 — — (690 ) 14,310 Total $ (3,113 ) $ 143,859 $ (619 ) $ 10,885 $ (3,732 ) $ 154,744 Our investment portfolio is comprised primarily of mortgage-backed securities issued by Ginnie Mae, Fannie Mae and Freddie Mac, with amortized costs of $ 110.2 million, $ 70.8 million, and $ 46.6 million, respectively, at December 31, 2017 . We own these securities to meet our requirements under the Community Reinvestment Act. As of December 31, 2017 , there were 62 of 92 separate mortgage-backed securities with unrealized losses in our investment portfolio. As of December 31, 2017 , 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 remaining securities in a net loss position carry a principal and interest guarantee by Fannie Mae. As of December 31, 2016 , there were 48 of 84 separate mortgage-backed securities with unrealized losses in our investment portfolio. Twenty-one of the 48 securities in a net loss position were issued by Ginnie Mae. 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. We also invest in Utah Housing Corporation bonds for the purpose of complying with the Community Reinvestment Act. These bonds are Aa3 rated by Moody’s Investors Service. The amortized cost of the investment on the consolidated balance sheet at December 31, 2017 was $ 20 million. 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 December 31, 2017 , 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 $ 272 $ 293 2039 3,406 3,606 2042 10,993 10,487 2043 37,438 37,534 2044 28,301 28,206 2045 41,082 40,484 2046 48,785 47,771 2047 77,330 75,707 Total $ 247,607 $ 244,088 The mortgage-backed securities have been pledged to the FRB as collateral against any advances and accrued interest under the Primary Credit lending program sponsored by the FRB. We had $218.4 million and $ 188.0 million par value of mortgage-backed securities pledged to this borrowing facility at December 31, 2017 and 2016 , respectively, as discussed further in Note 9, “Borrowings.”

Loans Held for Investment

Loans Held for Investment	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Loans Held for Investment	Loans Held for Investment Loans Held for Investment consist of Private Education Loans, FFELP Loans and Personal Loans. 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 rate indexed to LIBOR. As of December 31, 2017 and 2016, 77 percent and 81 percent , respectively, 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. 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. For loans disbursed prior to October 1, 1993, we receive 100 percent reimbursement. Loans held for investment are summarized as follows: December 31, 2017 2016 Private Education Loans $ 17,432,167 $ 14,251,675 Deferred origination costs 56,378 44,206 Allowance for loan losses (243,715 ) (182,472 ) Total Private Education Loans, net 17,244,830 14,113,409 FFELP Loans 927,660 1,010,908 Unamortized acquisition costs, net 2,631 2,941 Allowance for loan losses (1,132 ) (2,171 ) Total FFELP Loans, net 929,159 1,011,678 Personal Loans 400,280 12,893 Allowance for loan losses (6,628 ) (58 ) Total Personal Loans, net 393,652 12,835 Loans held for investment, net $ 18,567,641 $ 15,137,922 The estimated weighted average life of education loans in our portfolio was approximately 5.5 years and 6.0 years at December 31, 2017 and 2016 , respectively. The average balance and the respective weighted average interest rates of loans in our portfolio are summarized as follows: Years Ended December 31, 2017 2016 2015 Average Balance Weighted Average Interest Rate Average Balance Weighted Average Interest Rate Average Balance Weighted Average Interest Rate Private Education Loans $ 16,176,351 8.43 % $ 12,747,756 8.02 % $ 9,819,053 7.93 % FFELP Loans 970,738 3.91 1,063,325 3.53 1,179,723 3.26 Personal Loans 112,644 9.90 710 8.53 — — Total portfolio $ 17,259,733 $ 13,811,791 $ 10,998,776 Certain Collection Tools — Private Education Loans Forbearance involves granting the customer a temporary cessation of payments (or temporary acceptance of smaller than scheduled payments) for a specified period of time. Using forbearance extends the original term of the loan. Forbearance does not grant any reduction in the total repayment obligation (principal or interest). While in forbearance status, interest continues to accrue and is capitalized to principal when the loan re-enters repayment status. Our forbearance policies include limits on the number of forbearance months granted consecutively and the total number of forbearance months granted over the life of the loan. We grant forbearance in our servicing centers if a borrower who is current requests it for increments of three months at a time, for up to twelve months. Forbearance as a collection tool is used most effectively when applied based on a customer’s unique situation, including historical information and judgments. We leverage updated customer information and other decision support tools to best determine who will be granted forbearance based on our expectations as to a customer’s ability and willingness to repay their obligation. This strategy is aimed at mitigating the overall risk of the portfolio as well as encouraging cash resolution of delinquent loans. In some instances, we require good-faith payments before granting forbearance. Exceptions to forbearance policies are permitted when such exceptions are judged to increase the likelihood of collection of the loan. Forbearance may be granted to customers who are exiting their grace period to provide additional time to obtain employment and income to support their obligations, or to current customers who are faced with a hardship and request forbearance time to provide temporary payment relief. In these circumstances, a customer’s loan is placed into a forbearance status in limited monthly increments and is reflected in the forbearance status at month-end during this time. At the end of the granted forbearance period, the customer will enter repayment status as current and is expected to begin making scheduled monthly payments on a go-forward basis. Forbearance may also be granted to customers who are delinquent in their payments. If specific requirements are met, the forbearance can cure the delinquency and the customer is returned to a current repayment status. In more limited instances, delinquent customers will also be granted additional forbearance time. We also have an interest rate reduction program to assist customers in repaying their Private Education Loans through reduced payments, while continuing to reduce their outstanding principal balance. This program is offered in situations where the potential for principal recovery, through an interest rate reduction that results in a lower monthly payment amount, is more suitable than other alternatives currently available. As part of demonstrating the ability and willingness to pay, the customer must make three consecutive monthly payments at the reduced rate to qualify for the program. Once the customer has made the initial three payments, the loan’s status is returned to current and the interest rate is reduced for a twenty-four month period. The period of delinquency for loans is based on the number of days scheduled payments are contractually past due. As of December 31, 2017 and 2016 , we had $66.9 million and $67.5 million, respectively, of FFELP Loans and $37.6 million and $24.2 million, respectively, of Private Education Loans held for investment which were more than 90 days delinquent that continue to accrue interest. At December 31, 2017 and 2016 , we had no loans in nonaccrual status. Borrower-in-Custody Arrangements We maintain Borrower-in-Custody arrangements with the FRB. Under these arrangements, we can pledge FFELP consolidation loans or Private Education Loans to the FRB to secure any advances and accrued interest generated under the Primary Credit program at the FRB. As of December 31, 2017 and 2016 , we had $2.7 billion and $2.7 billion, respectively, of Private Education Loans pledged to this borrowing facility, as discussed further in Note 9, “Borrowings.” Loans Held for Investment by Region At December 31, 2017 , 40.4 percent of total education loans were concentrated in the following states: 2017 New York 10.5 % California 9.3 Pennsylvania 8.5 New Jersey 6.9 Illinois 5.2 40.4 % At December 31, 2016 , 40.3 percent of total education loans were concentrated in the following states: 2016 New York 10.3 % California 9.4 Pennsylvania 8.4 New Jersey 6.9 Illinois 5.3 40.3 % No other state had a concentration of total education loans in excess of 5 percent of the aggregate outstanding education loans held for investment.

Allowance for Loan Losses

Allowance for Loan Losses	12 Months Ended
	Dec. 31, 2017
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. See Note 2, “Significant Accounting Policies — Allowance for Loan Losses — Allowance for Private Education Loan Losses, — Allowance for Personal Loans and — Allowance for FFELP Loan Losses” for a more detailed discussion. Allowance for Loan Losses Metrics Allowance for Loan Losses Year Ended December 31, 2017 FFELP Loans Private Education Loans Personal Loans Total Allowance for Loan Losses Beginning balance $ 2,171 $ 182,472 $ 58 $ 184,701 Total provision (85 ) 178,542 7,138 185,595 Net charge-offs: Charge-offs (954 ) (130,063 ) (579 ) (131,596 ) Recoveries — 17,635 11 17,646 Net charge-offs (954 ) (112,428 ) (568 ) (113,950 ) Loan sales (1) — (4,871 ) — (4,871 ) Ending Balance $ 1,132 $ 243,715 $ 6,628 $ 251,475 Allowance: Ending balance: individually evaluated for impairment $ — $ 94,682 $ — $ 94,682 Ending balance: collectively evaluated for impairment $ 1,132 $ 149,033 $ 6,628 $ 156,793 Loans: Ending balance: individually evaluated for impairment $ — $ 990,351 $ — $ 990,351 Ending balance: collectively evaluated for impairment $ 927,660 $ 16,441,816 $ 400,280 $ 17,769,756 Net charge-offs as a percentage of average loans in repayment (2) 0.13 % 1.03 % 0.47 % Allowance as a percentage of the ending total loan balance 0.12 % 1.40 % 1.66 % Allowance as a percentage of the ending loans in repayment (2) 0.15 % 2.00 % 1.66 % Allowance coverage of net charge-offs 1.19 2.17 11.67 Ending total loans, gross $ 927,660 $ 17,432,167 $ 400,280 Average loans in repayment (2) $ 745,039 $ 10,881,058 $ 119,606 Ending loans in repayment (2) $ 746,456 $ 12,206,033 $ 400,280 ____________ (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 Year Ended December 31, 2016 FFELP Loans Private Education Loans Personal Loans Total Allowance for Loan Losses Beginning balance $ 3,691 $ 108,816 $ — $ 112,507 Total provision (172 ) 159,511 58 159,397 Net charge-offs: Charge-offs (1,348 ) (90,203 ) — (91,551 ) Recoveries — 10,382 — 10,382 Net charge-offs (1,348 ) (79,821 ) — (81,169 ) Loan sales (1) — (6,034 ) — (6,034 ) Ending Balance $ 2,171 $ 182,472 $ 58 $ 184,701 Allowance: Ending balance: individually evaluated for impairment $ — $ 86,930 $ — $ 86,930 Ending balance: collectively evaluated for impairment $ 2,171 $ 95,542 $ 58 $ 97,771 Loans: Ending balance: individually evaluated for impairment $ — $ 612,606 $ — $ 612,606 Ending balance: collectively evaluated for impairment $ 1,010,908 $ 13,639,069 $ 12,894 $ 14,662,871 Net charge-offs as a percentage of average loans in repayment (2) 0.17 % 0.96 % — % Allowance as a percentage of the ending total loan balance 0.21 % 1.28 % — % Allowance as a percentage of the ending loans in repayment (2) 0.28 % 1.88 % — % Allowance coverage of net charge-offs 1.61 2.29 — Ending total loans, gross $ 1,010,908 $ 14,251,675 $ — Average loans in repayment (2) $ 793,203 $ 8,283,036 $ — Ending loans in repayment (2) $ 786,332 $ 9,709,758 $ — ____________ (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 Year Ended December 31, 2015 FFELP Loans Private Education Loans Total Allowance for Loan Losses Beginning balance $ 5,268 $ 78,574 $ 83,842 Total provision 1,005 87,344 88,349 Net charge-offs: Charge-offs (2,582 ) (55,357 ) (57,939 ) Recoveries — 5,820 5,820 Net charge-offs (2,582 ) (49,537 ) (52,119 ) Loan sales (1) — (7,565 ) (7,565 ) Ending Balance $ 3,691 $ 108,816 $ 112,507 Allowance: Ending balance: individually evaluated for impairment $ — $ 43,480 $ 43,480 Ending balance: collectively evaluated for impairment $ 3,691 $ 65,336 $ 69,027 Loans: Ending balance: individually evaluated for impairment $ — $ 265,831 $ 265,831 Ending balance: collectively evaluated for impairment $ 1,115,663 $ 10,330,606 $ 11,446,269 Net charge-offs as a percentage of average loans in repayment (2) 0.30 % 0.82 % Allowance as a percentage of the ending total loan balance 0.33 % 1.03 % Allowance as a percentage of the ending loans in repayment (2) 0.45 % 1.57 % Allowance coverage of net charge-offs 1.43 2.20 Ending total loans, gross $ 1,115,663 $ 10,596,437 Average loans in repayment (2) $ 857,359 $ 6,031,741 Ending loans in repayment (2) $ 813,815 $ 6,927,266 ____________ (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 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 may increase the ability and willingness of a borrower to make payments and thus increase the ultimate overall amount collected on a 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. Once a loan qualifies for TDR status, it remains a TDR for allowance purposes for the remainder of its life. As of December 31, 2017 and 2016, approximately 66 percent and 69 percent , respectively, of TDRs were classified as such due to their forbearance status. See Note 2, “Significant Accounting Policies — Allowance for Loan Losses” for a more detailed discussion. 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 standpoint at any point in their life cycle prior to claim payment, and we continue to accrue interest through the date of claim. At December 31, 2017 and 2016 , all of our 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 December 31, 2017 TDR Loans $ 1,007,141 $ 990,351 $ 94,682 December 31, 2016 TDR Loans $ 620,991 $ 612,606 $ 86,930 The following table provides the average recorded investment and interest income recognized for our TDR loans. Years Ended December 31, 2017 2016 2015 Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized TDR Loans $ 822,145 $ 61,119 $ 422,527 $ 30,700 $ 174,087 $ 14,081 The following table provides information regarding the loan status and aging of TDR loans. December 31, December 31, 2017 2016 Balance % Balance % TDR loans in in-school/grace/deferment (1) $ 51,745 $ 24,185 TDR loans in forbearance (2) 69,652 71,851 TDR loans in repayment (3) and percentage of each status: Loans current 774,222 89.1 % 462,187 89.5 % Loans delinquent 31-60 days (4) 48,377 5.6 28,452 5.5 Loans delinquent 61-90 days (4) 28,778 3.3 17,326 3.4 Loans delinquent greater than 90 days (4) 17,577 2.0 8,605 1.6 Total TDR loans in repayment 868,954 100.0 % 516,570 100.0 % Total TDR loans, gross $ 990,351 $ 612,606 _____ (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 includes 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 60 days past due for this disclosure. Years Ended December 31, 2017 2016 2015 Modified Loans (1) Charge-offs Payment-Default Modified Loans (1) Charge-offs Payment-Default Modified Loans (1) Charge-offs Payment-Default TDR Loans $ 498,812 $ 48,469 $ 92,532 $ 398,324 $ 24,628 $ 64,811 $ 244,890 $ 10,877 $ 51,602 _______ (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. December 31, 2017 December 31, 2016 Credit Quality Indicators: Balance (1) % of Balance Balance (1) % of Balance Cosigners: With cosigner $ 15,658,539 90 % $ 12,816,512 90 % Without cosigner 1,773,628 10 1,435,163 10 Total $ 17,432,167 100 % $ 14,251,675 100 % FICO at Original Approval (2) : Less than 670 $ 1,153,591 6 % $ 920,132 6 % 670-699 2,596,959 15 2,092,722 15 700-749 5,714,554 33 4,639,958 33 Greater than or equal to 750 7,967,063 46 6,598,863 46 Total $ 17,432,167 100 % $ 14,251,675 100 % Seasoning (3) : 1-12 payments $ 4,256,592 24 % $ 3,737,110 26 % 13-24 payments 3,229,465 19 2,841,107 20 25-36 payments 2,429,238 14 1,839,764 13 37-48 payments 1,502,327 9 917,633 7 More than 48 payments 1,256,813 7 726,106 5 Not yet in repayment 4,757,732 27 4,189,955 29 Total $ 17,432,167 100 % $ 14,251,675 100 % ___________ (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. Personal Loan Key Credit Quality Indicators For Personal Loans, the key credit quality indicators are FICO scores 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 Personal Loan portfolio stratified by key credit quality indicators. Personal Loans Credit Quality Indicators December 31, 2017 December 31, 2016 Credit Quality Indicators: Balance (1) % of Balance Balance (1) % of Balance FICO at Original Approval: Less than 670 $ 32,156 8 % $ 1,189 9 % 670-699 114,731 29 3,139 24 700-749 182,025 45 5,678 44 Greater than or equal to 750 71,368 18 2,888 23 Total $ 400,280 100 % $ 12,894 100 % Seasoning (2) : 0-12 payments $ 400,280 100 % $ 12,894 100 % 13-24 payments — — — — 25-36 payments — — — — 37-48 payments — — — — More than 48 payments — — — — Total $ 400,280 100 % $ 12,894 100 % ___________ (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 Private Education Loans. 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. Private Education Loans December 31, 2017 2016 2015 Balance % Balance % Balance % Loans in-school/grace/deferment (1) $ 4,757,732 $ 4,189,955 $ 3,427,964 Loans in forbearance (2) 468,402 351,962 241,207 Loans in repayment and percentage of each status: Loans current 11,911,128 97.6 % 9,509,394 97.9 % 6,773,095 97.8 % Loans delinquent 31-60 days (3) 179,002 1.5 124,773 1.3 91,129 1.3 Loans delinquent 61-90 days (3) 78,292 0.6 51,423 0.5 42,048 0.6 Loans delinquent greater than 90 days (3) 37,611 0.3 24,168 0.3 20,994 0.3 Total Private Education Loans in repayment 12,206,033 100.0 % 9,709,758 100.0 % 6,927,266 100.0 % Total Private Education Loans, gross 17,432,167 14,251,675 10,596,437 Private Education Loans deferred origination costs 56,378 44,206 27,884 Total Private Education Loans 17,488,545 14,295,881 10,624,321 Private Education Loans allowance for losses (243,715 ) (182,472 ) (108,816 ) Private Education Loans, net $ 17,244,830 $ 14,113,409 $ 10,515,505 Percentage of Private Education Loans in repayment 70.0 % 68.1 % 65.4 % Delinquencies as a percentage of Private Education Loans in repayment 2.4 % 2.1 % 2.2 % Loans in forbearance as a percentage of Private Education Loans in repayment and forbearance 3.7 % 3.5 % 3.4 % (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. 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 portfolio for all periods presented. Private Education Loan Accrued Interest Receivable Total Interest Receivable Greater Than 90 Days Past Due Allowance for Uncollectible Interest December 31, 2017 $ 951,138 $ 1,372 $ 4,664 December 31, 2016 $ 739,847 $ 845 $ 2,898

Premises and Equipment, Net

Premises and Equipment, Net	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Premises and Equipment, net	Premises and Equipment, net The following is a summary of our premises and equipment. December 31, 2017 2016 Land and land improvements $ 12,356 $ 12,574 Buildings and leasehold improvements 61,409 60,919 Furniture, fixtures and equipment 15,261 15,026 Software 55,205 47,688 Premises and equipment, gross 144,231 136,207 Accumulated depreciation (54,483 ) (49,144 ) Premises and equipment, net $ 89,748 $ 87,063 Depreciation expense for premises and equipment was $11.2 million, $9.6 million and $7.4 million for the years ended December 31, 2017 , 2016 and 2015 , respectively.

Deposits

Deposits	12 Months Ended
	Dec. 31, 2017
Deposits [Abstract]
Deposits	Deposits The following table summarizes total deposits at December 31, 2017 and 2016 . December 31, 2017 2016 Deposits - interest bearing $ 15,504,330 $ 13,434,990 Deposits - non-interest bearing 1,053 677 Total deposits $ 15,505,383 $ 13,435,667 Our total deposits of $15.5 billion were comprised of $8.2 billion in brokered deposits and $7.3 billion in retail and other deposits at December 31, 2017, compared to total deposits of $13.4 billion , which were comprised of $7.1 billion in brokered deposits and $6.3 billion in retail and other deposits, at December 31, 2016. Interest bearing deposits as of December 31, 2017 and 2016 consisted of retail non-maturity savings deposits, retail and brokered MMDAs, and brokered and retail CDs. Interest bearing deposits include deposits from Educational 529 and Health Savings plans that diversify our funding sources and add deposits we consider to be core. These and other large omnibus accounts, aggregating the deposits of many individual depositors, represented $ 5.5 billion of our deposit total as of December 31, 2017, compared with $5.4 billion at December 31, 2016. 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 $9.4 million, $10.1 million, and $10.5 million in the years ended December 31, 2017 , 2016 and 2015 , respectively. Fees paid to third-party brokers related to these CDs were $12.2 million, $4.4 million, and $4.1 million during the years ended December 31, 2017 , 2016 and 2015 , respectively. Interest bearing deposits at December 31, 2017 and 2016 are summarized as follows: December 31, 2017 December 31, 2016 Amount Year-End Weighted Average Stated Rate (1) Amount Year-End Weighted Average Stated Rate (1) Money market $ 7,731,966 1.80 % $ 7,129,404 1.22 % Savings 738,243 1.10 % 834,521 0.84 % Certificates of deposit 7,034,121 1.93 % 5,471,065 1.41 % Deposits - interest bearing $ 15,504,330 $ 13,434,990 ___ (1) Includes the effect of interest rate swaps in effective hedge relationships. Certificates of deposit remaining maturities are summarized as follows: December 31, 2017 2016 One year or less $ 3,716,183 $ 2,565,246 After one year to two years 1,550,130 1,364,812 After two years to three years 806,488 936,125 After three years to four years 447,592 225,245 After four years to five years 445,884 379,637 After five years 67,844 — Total $ 7,034,121 $ 5,471,065 As of December 31, 2017 and 2016 , there were $395.5 million and $304.5 million of deposits exceeding FDIC insurance limits. Accrued interest on deposits was $27.8 million and $18.9 million at December 31, 2017 and 2016 , respectively.

Borrowings

Borrowings	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Borrowings	Borrowings Outstanding borrowings consist of unsecured debt and secured borrowings issued through our term ABS program and our ABCP Facility. The following table summarizes our secured borrowings at December 31, 2017 and 2016. December 31, 2017 December 31, 2016 Short-Term Long-Term Total Short-Term Long-Term Total Unsecured borrowings: Unsecured debt $ — $ 196,539 $ 196,539 $ — $ — $ — Total unsecured borrowings — 196,539 196,539 — — — Secured borrowings: Private Education Loan term securitizations — 3,078,731 3,078,731 — 2,167,979 2,167,979 ABCP Facility — — — — — — Total secured borrowings — 3,078,731 3,078,731 — 2,167,979 2,167,979 Total $ — $ 3,275,270 $ 3,275,270 $ — $ 2,167,979 $ 2,167,979 Short-term Borrowings Asset-Backed Commercial Paper Funding Facility On February 22, 2017 and 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). For additional information, see Note 24, “Subsequent Events.” At December 31, 2017 , there were no borrowings outstanding under the ABCP Facility. Short-term borrowings have a remaining term to maturity of one year or less. The following table summarizes the outstanding short-term borrowings, the weighted average interest rates at the end of the period and the related average balance and weighted average interest rates during the period. The ABCP Facility’s contractual maturity is two years from the date of inception or renewal ( one -year revolving period plus a one -year amortization period); however, we classify advances under our ABCP Facility as short-term borrowings because it is our intention to repay those advances within one year. Rates reflect stated interest of borrowings and related discounts and premiums. December 31, 2017 Year Ended December 31, 2017 Ending Balance Weighted Average Interest Rate Average Balance Weighted Average Interest Rate Short-term borrowings: ABCP Facility $ — — % $ 81,370 6.09 % Maximum outstanding at any month end $ 300,000 December 31, 2016 Year Ended December 31, 2016 Ending Balance Weighted Average Interest Rate Average Balance Weighted Average Interest Rate Short-term borrowings: ABCP Facility $ — — % $ 229,719 2.61 % Maximum outstanding at any month end $ 526,500 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 December 31, 2017, the outstanding balance was $197 million . Secured Financings 2017 Transactions On February 8, 2017, we executed our $772 million SMB Private Education Loan Trust 2017-A term ABS transaction, which was accounted for as a secured financing. We sold $772 million of notes to third parties and retained a 100 percent interest in the residual certificates issued in the securitization, raising approximately $768 million of gross proceeds. The Class A and Class B notes had a weighted average life of 4.27 years and priced at a weighted average LIBOR equivalent cost of 1-month LIBOR plus 0.93 percent . At December 31, 2017, $733 million of our Private Education Loans were encumbered as a result of this transaction. On November 8, 2017, we executed our $676 million SMB Private Education Loan Trust 2017-B term ABS transaction, which was accounted for as a secured financing. We sold $676 million of notes to third parties and retained a 100 percent interest in the residual certificates issued in the securitization, raising approximately $674 million of gross proceeds. The Class A and Class B notes had a weighted average life of 4.07 years and priced at a weighted average LIBOR equivalent cost of 1-month LIBOR plus 0.80 percent . At December 31, 2017, $698 million of our Private Education Loans were encumbered as a result of this transaction. 2016 Transactions On May 26, 2016, we executed our SMB Private Education Loan Trust 2016-A term ABS transaction, which was accounted for as a secured financing. A total of $551 million of notes were issued in connection with the transaction. We retained a 100 percent or $50 million interest in the Class B notes and 100 percent of the residual certificates issued in the securitization. $501 million of Class A notes from the securitization were sold to third parties, raising $501 million of gross proceeds. The Class A notes had a weighted average life of 4.01 years and priced at a weighted average LIBOR equivalent cost of 1-month LIBOR plus 1.38 percent . At December 31, 2017, $ 501 million of our Private Education Loans were encumbered as a result of this transaction. On July 21, 2016, we executed our SMB Private Education Loan Trust 2016-B term ABS transaction, which was accounted for as a secured financing. A total of $657 million of notes were issued in connection with the transaction. We retained a 100 percent or $50 million interest in the Class B notes and 100 percent of the residual certificates issued in the securitization. $607 million of Class A notes from the securitization were sold to third parties, raising $607 million of gross proceeds. The Class A notes had a weighted average life of 4.01 and priced at a weighted average LIBOR equivalent cost of 1-month LIBOR plus 1.36 percent . At December 31, 2017, $ 605 million of our Private Education Loans were encumbered as a result of this transaction. On October 12, 2016, we executed our SMB Private Education Loan Trust 2016-C term ABS transaction, which was accounted for as a secured financing. A total of $674 million of notes were issued in connection with the transaction. We retained a 100 percent interest in the residual certificates issued in the securitization. $674 million of notes from the securitization were sold to third-parties, raising $673 million of gross proceeds. The Class A and Class B notes had a weighted average life of 4.27 years and priced at a weighted average LIBOR equivalent cost of 1-month LIBOR plus 1.15 percent. At December 31, 2017, $ 612 million of our Private Education Loans were encumbered as a result of this transaction. The following table summarizes the outstanding long-term borrowings, the weighted average interest rates at the end of the period and the related average balance during the period. Rates reflect stated interest of borrowings and related discounts and premiums. The long-term borrowings amortize over time and mature serially from 2023 to 2040. December 31, 2017 Year Ended December 31, 2016 Year Ended December 31, 2016 Ending Balance Weighted Average Average Balance Ending Balance Weighted Average Interest Rate Average Balance Floating rate borrowings $ 1,512,970 2.32 % $ 1,422,856 $ 1,175,819 1.71 % $ 687,580 Fixed rate borrowings 1,762,300 3.04 1,420,737 992,160 2.68 548,465 Total long-term borrowings $ 3,275,270 2.71 % $ 2,843,593 $ 2,167,979 2.15 % $ 1,236,045 Secured Financings 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 loans 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 I month LIBOR plus 0.80% 4.07 — Total notes issued in 2017 $ 1,448,000 Total loans and accrued interest amount securitized at inception in 2017 $ 1,606,804 ____________ (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. 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 December 31, 2016 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 $ — $ 2,167,979 $ 2,167,979 $ 2,562,156 $ 44,617 $ 160,783 $ 2,767,556 ABCP Facility — — — — — — — Total $ — $ 2,167,979 $ 2,167,979 $ 2,562,156 $ 44,617 $ 160,783 $ 2,767,556 ________ (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 December 31, 2017. 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 years ended December 31, 2017 and 2016. 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 asset-backed and mortgage-backed securities, as well as FFELP Loans and Private Education Loans, to the FRB as collateral for borrowings at the Window. Generally, collateral value is assigned based on the estimated fair value of the pledged assets. At December 31, 2017 and December 31, 2016, the value of our pledged collateral at the FRB was $ 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 years ended December 31, 2017 and 2016.

Private Education Loan Term Sec

Private Education Loan Term Securitizations Private Education Loan Term Securitizations	12 Months Ended
	Dec. 31, 2017
Transfers and Servicing [Abstract]
Private Education Loan Term Securitizations	Private Education Loan Term Securitizations We securitize Private Education Loan assets by selling these assets to securitization trusts. If we have a variable interest in a VIE (e.g., a securitization trust) and have determined that we are the primary beneficiary, then we will consolidate the VIE and the transfer is accounted for as a financing. For additional information, see Note 9, “Borrowings.” If a transfer of loans qualifies as a sale, we derecognize the loan and recognize a gain or loss as the difference between compensation received and the carrying basis of the loans sold and liabilities retained. We recognize the results of a transfer of loans based upon the settlement date of the transaction. On October 27, 2015, we executed a $ 701 million Private Education Loan term ABS transaction that qualified for sale treatment and removed the principal balance of the loans backing the securitization trust from our balance sheet on the settlement date. We continue to service the loans in the trust. In the fourth quarter of 2015, we recorded a pre-tax gain of $ 58 million on the sale, net of closing adjustments and transaction costs, a 7.8 percent premium. On April 23, 2015, we executed a $ 738 million Private Education Loan term ABS transaction that qualified for sale treatment and removed the principal balance of the loans backing the securitization trust from our balance sheet on the settlement date. We continue to service the loans in the trust. In the second quarter of 2015, we recorded a pre-tax gain of $ 77 million on the sale, net of closing adjustments and transaction costs, a 10.4 percent premium.

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Derivative Financial Instruments 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. Although we use derivatives to reduce the risk of interest rate changes, the use of derivatives does expose us to both market and credit risk. Market risk is the chance of financial loss resulting from changes in interest rates and market liquidity. Credit risk is the risk that a counterparty will not perform its obligations under a contract and it is limited to the loss of the fair value gain in a derivative that the counterparty owes us less collateral held and plus collateral posted. When the fair value of a derivative contract less collateral held and plus collateral posted is negative, we owe the counterparty and, therefore, we have no credit risk exposure to the counterparty; however, the counterparty has exposure to us. We minimize the credit risk in derivative instruments by entering into transactions with reputable counterparties that are reviewed regularly by our Credit Department. We also maintain a policy of requiring that all derivative contracts be governed by an International Swaps and Derivatives Association, Inc. Master Agreement. Depending on the nature of the derivative transaction, bilateral collateral arrangements are required as well. When we have more than one outstanding derivative transaction with the counterparty, and there exists legally enforceable netting provisions with the counterparty (i.e., a legal right to offset receivable and payable derivative contracts), the “net” mark-to-market exposure, less collateral held and plus collateral posted, represents exposure with the counterparty. We refer to this as the “net position.” When there is a net negative exposure, we consider our exposure to the counterparty and the net position to be zero. Title VII of the Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010 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 CME and the 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, result in all variation margin payments on derivatives cleared through the CME being accounted for as legal settlement, while the LCH allows the clearing member institution the option to adopt the rule changes on an individual contract or portfolio basis. As of December 31, 2017, $ 4.8 billion notional of our derivative contracts were cleared on the CME and $0.7 billion were cleared on the LCH. The derivative contracts cleared through the CME and LCH represent 87.6 percent and 12.4 percent , respectively, of our total notional derivative contracts of $ 5.5 billion at December 31, 2017. Under this new rule, for derivatives cleared through the CME, 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 LCH clearing member institution has elected not to adopt the new rule change. Therefore, there has been no change to the accounting for the derivatives cleared through the LCH, and variation margin payments required to be exchanged based on the fair value of those derivatives remain accounted for as collateral. 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 December 31, 2017 and 2016 , 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 $19.6 million and $44.6 million, respectively. Accounting for Derivative Instruments 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, and 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 debt into variable-rate debt. 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. Cash Flow Hedges We use cash flow hedges to hedge the exposure to variability in cash flows of floating-rate deposits. This strategy is used primarily to minimize the exposure to volatility in cash flows from future changes in interest rates. Gains and losses on the effective portion of a qualifying hedge are recorded in accumulated other comprehensive income and ineffectiveness is recorded immediately to earnings. 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. 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 $ 1.8 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 our derivative instruments entered into after December 31, 2013 with a maturity 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. Summary of Derivative Financial Statement Impact The following tables summarize the fair values and notional amounts of all derivative instruments at December 31, 2017 and 2016 , and their impact on earnings and other comprehensive income for the years ended December 31, 2017 , 2016 and 2015 . The net fair value of derivative instruments as of December 31, 2017 was a liability of $1.8 million , compared to the net fair value as of December 31, 2016 liability of $18.1 million . The change in the net fair value reflects a $3.5 million decrease in fair value offset by variation margin amounts of $19.9 million . The net position as of December 31, 2017 was a $19.8 million liability, compared to a $30.0 million liability as of December 31, 2016. The change in the net position reflects a $3.5 million decrease in fair value, $32.1 million decrease in collateral held and pledged (for contracts other than those cleared through the CME), offset by variation margin impacts of $25.4 million . Impact of Derivatives on the Consolidated Balance Sheets Cash Flow Hedges Fair Value Hedges Trading Total December 31, December 31, December 31, December 31, December 31, December 31, December 31, December 31, 2017 2016 2017 2016 2017 2016 2017 2016 Fair Values (1) Hedged Risk Exposure Derivative Assets: (2) Interest rate swaps Interest rate $ — $ — $ 630 $ 7,808 $ 182 $ — $ 812 $ 7,808 Derivative Liabilities: (2) Interest rate swaps Interest rate (2,584 ) (14,463 ) — (10,398 ) — (1,076 ) (2,584 ) (25,937 ) Total net derivatives $ (2,584 ) $ (14,463 ) $ 630 $ (2,590 ) $ 182 $ (1,076 ) $ (1,772 ) $ (18,129 ) (1) Except for instruments cleared through the CME, fair values reported are exclusive of collateral held and pledged 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. The net position includes the variation margin as legal settlement of the derivative contract for instruments cleared through the CME. (2) The following table reconciles gross positions with the impact of master netting agreements to the balance sheet classification: Other Assets Other Liabilities December 31, December 31, December 31, December 31, 2017 2016 2017 2016 Gross position (1) $ 812 $ 7,808 $ (2,584 ) $ (25,937 ) Impact of master netting agreement (812 ) (7,808 ) 812 7,808 Derivative values with impact of master netting agreements (as carried on balance sheet) — — (1,772 ) (18,129 ) Cash collateral (held) pledged (2) — — 21,586 48,134 Net position $ — $ — $ 19,814 $ 30,005 (1) Except for instruments cleared with the CME, gross position amounts are exclusive of accrued interest and collateral held and pledged. (2) Cash collateral (held) pledged excludes amounts that represent legal settlement of the derivative contracts. Cash Flow Fair Value Trading Total December 31, December 31, December 31, December 31, December 31, December 31, December 31, December 31, 2017 2016 2017 2016 2017 2016 2017 2016 Notional Values Interest rate swaps $ 1,408,649 $ 1,054,688 $ 3,062,849 $ 3,628,062 $ 987,577 $ 494,638 $ 5,459,075 $ 5,177,388 Impact of Derivatives on the Consolidated Statements of Income Years Ended December 31, 2017 2016 2015 Fair Value Hedges Interest rate swaps: Hedge ineffectiveness realized gains (losses) recorded in earnings (1) $ (4,557 ) $ (1,035 ) $ 2,695 Realized gains recorded in interest expense 8,286 27,810 29,940 Total $ 3,729 $ 26,775 $ 32,635 Cash Flow Hedges Interest rate swaps: Hedge ineffectiveness gains (losses) recorded in earnings (1) $ 53 $ (1,579 ) $ (1,427 ) Realized losses recorded in interest expense (11,187 ) (17,665 ) (21,475 ) Total $ (11,134 ) $ (19,244 ) $ (22,902 ) Trading Interest rate swaps: Interest reclassification $ (69 ) $ 2,170 $ 3,451 Realized gains (losses) recorded in earnings (3,693 ) (513 ) 581 Total (1) (3,762 ) 1,657 4,032 Total $ (11,167 ) $ 9,188 $ 13,765 _______ (1) Amounts included in “gains (losses) on derivatives and hedging activities, net” in the consolidated statements of income. Impact of Derivatives on the Statements of Changes in Stockholders’ Equity Years Ended December 31, 2017 2016 2015 Amount of gain (loss) recognized in other comprehensive income (loss) $ 8,008 $ (3,901 ) $ (26,699 ) Amount of loss reclassified in interest expense (1) (11,187 ) (17,665 ) (21,475 ) Total change in other comprehensive income (loss) for unrealized gains (losses) on derivatives, before income tax (expense) benefit $ 19,195 $ 13,764 $ (5,224 ) ______ (1) Amounts included in “realized losses recorded in interest expense” in the “Impact of Derivatives on the Consolidated Statements of Income” table. Cash Collateral As of December 31, 2017, cash collateral held and pledged excludes amounts that represent legal settlement of the derivative contracts held with the CME. Cash collateral held related to derivative exposure between us and our derivatives counterparties was $0 and $1.0 million at December 31, 2017 and 2016 , respectively. 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 $21.6 million and $49.1 million at December 31, 2017 and 2016 , respectively. Collateral pledged is recorded in “Other interest-earning assets” on the consolidated balance sheets.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Preferred Stock On May 5, 2017, we redeemed, with the proceeds from our unsecured debt offering (see Note 9, “Borrowings”), the outstanding 3.3 million shares of our 6.97 percent Cumulative Redeemable Preferred Stock, Series A (the “Series A Preferred Stock”). The Series A Preferred Stock was redeemed at a price of $ 50 per share, plus accrued and unpaid dividends from May 1, 2017 to, but excluding, the May 5, 2017 redemption date. At December 31, 2017 , we had 4.0 million shares of Floating-Rate Non-Cumulative Preferred Stock, Series B (the “Series B Preferred Stock”) outstanding. The Series B Preferred Stock does not have a maturity date, but can be redeemed at our option. Redemption would include any accrued and unpaid dividends for the then current quarterly dividend period, up to the redemption date. The shares have no preemptive or conversion rights and are not exchangeable for any of our other securities or property. Dividends are not mandatory and are paid quarterly, when, as, and if declared by the Board of Directors. Holders of Series B Preferred Stock are entitled to receive quarterly dividends based on 3-month LIBOR plus 170 basis points per annum in arrears. Upon liquidation or dissolution of the Company, holders of the Series B Preferred Stock are entitled to receive $ 100 per share, plus an amount equal to accrued and unpaid dividends for the then current quarterly dividend period, pro rata, and before any distribution of assets are made to holders of our common stock. Common Stock Our shareholders have authorized the issuance of 1.125 billion shares of common stock (par value of $0 .20 ). At December 31, 2017 , 432 million shares were issued and outstanding and 46 million shares were unissued but encumbered for outstanding stock options, restricted stock units and dividend equivalent units for employee compensation and remaining authority for stock-based compensation plans. We did no t pay common stock dividends for the years ended December 31, 2017, 2016 and 2015. We currently do not intend to initiate a publicly-announced share repurchase program. We only expect to repurchase common stock acquired in connection with taxes withheld resulting from award exercises and vesting under our employee stock-based compensation plans. The following table summarizes our common share repurchases and issuances associated with these programs. Years Ended December 31, (Shares and per share amounts in actuals) 2017 2016 2015 Shares repurchased related to employee stock-based compensation plans (1) 3,358,417 3,354,730 3,008,913 Average purchase price per share $11.96 $7.83 $9.65 Common shares issued (2) 6,831,108 5,955,045 5,873,309 _________ (1) Comprises 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) Common shares issued under our various compensation and benefit plans. The closing price of our common stock on December 29, 2017 was $ 11.30 .

Earnings Per Common Share

Earnings Per Common Share	12 Months Ended
	Dec. 31, 2017
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. Years Ended December 31, (In thousands, except per share data) 2017 2016 2015 Numerator: Net income $ 288,934 $ 250,327 $ 274,284 Preferred stock dividends 15,714 21,204 19,595 Net income attributable to SLM Corporation common stock $ 273,220 $ 229,123 $ 254,689 Denominator: Weighted average shares used to compute basic EPS 431,216 427,876 425,574 Effect of dilutive securities: Dilutive effect of stock options, restricted stock, restricted stock units and Employee Stock Purchase Plan (“ESPP”) (1)(2) 7,335 5,043 6,660 Weighted average shares used to compute diluted EPS 438,551 432,919 432,234 Basic earnings per common share attributable to SLM Corporation $ 0.63 $ 0.54 $ 0.60 Diluted earnings per common share attributable to SLM Corporation $ 0.62 $ 0.53 $ 0.59 __________ (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 years ended December 31, 2017 , 2016 and 2015 , securities covering approximately 0 , 1 million and 2 million shares, respectively, were outstanding but not included in the computation of diluted earnings per share because they were anti-dilutive.

Stock-Based Compensation Plans

Stock-Based Compensation Plans and Arrangements	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation Plans and Arrangements	Stock-Based Compensation Plans and Arrangements Plan Summaries As of December 31, 2017 , we had one active stock-based compensation plan that provides for grants of equity awards to our employees and non-employee directors. We also maintained an Employee Stock Purchase Plan (the “ESPP”). Shares issued under these stock-based compensation plans may be either shares reacquired by us or shares that are authorized but unissued. The SLM Corporation 2012 Omnibus Incentive Plan was approved by shareholders on May 24, 2012. At December 31, 2017, 23 million shares, as adjusted to reflect the effects of the Spin-Off, were authorized to be issued from this plan. An amendment to the ESPP was approved by shareholders on May 24, 2012 that authorized the issuance of 6 million shares under the plan and kept the terms of the plan substantially the same. The number of shares authorized under the plan was subsequently adjusted to 15 million shares on June 25, 2014, to reflect the effects of the Spin-Off. Stock-Based Compensation The total stock-based compensation cost recognized in the consolidated statements of income for the years ended December 31, 2017 , 2016 and 2015 was $27.9 million, $22.9 million and $21.6 million, respectively. As of December 31, 2017 , there was $ 14.2 million of total unrecognized compensation expense related to unvested stock awards, which is expected to be recognized over a weighted average period of 1.4 years . We amortize compensation expense on a straight-line basis over the related vesting periods of each tranche of each award. Stock Options Stock options granted prior to 2012 expire 10 years after the grant date, and those granted since 2012 expire in 5 years. The exercise price must be equal to or greater than the market price of our common stock on the grant date. We have granted time-vested, price-vested and performance-vested options to our employees and non-employee directors. Time-vested options granted to management and non-management employees generally vest over three years . Price-vested options granted to management employees vest upon our common stock reaching a targeted closing price for a set number of days. Performance-vested options granted to management employees vest one-third per year for three years based on corporate earnings-related performance targets. Options granted to non-employee directors vest upon the director’s election to the Board. There were no options granted in the years ended December 31, 2017 , 2016 and 2015. The following table summarizes stock option activity for the year ended December 31, 2017 . (Dollars in thousands, except per share data) Number of Options Weighted Average Exercise Price per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (1) Outstanding at December 31, 2016 7,595,059 $ 10.43 Granted — — Exercised (2)(3) (2,693,347 ) 5.80 Canceled (440,719 ) 15.82 Outstanding at December 31, 2017 (4) 4,460,993 $ 11.34 1.2 years $ 26,413 Exercisable at December 31, 2017 4,460,993 $ 5.38 1.2 years $ 26,413 ____________ (1) The aggregate intrinsic value represents the total intrinsic value (the aggregate difference between our closing stock price on December 31, 2017 and the exercise price of in-the-money options) that would have been received by the option holders if all in-the-money options had been exercised on December 31, 2017. (2) The total intrinsic value of options exercised was $16.5 million, $9.3 million, and $13.7 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. (3) Cash of $0.1 million was received from option exercises for the year ended December 31, 2017. The actual tax benefit realized for the tax deductions from option exercises totaled $2.7 million for the year ended December 31, 2017. (4) For net-settled options, gross number is reflected. Restricted Stock Restricted stock awards generally vest over one year and in some cases based on corporate earnings-related performance targets. Outstanding restricted stock is entitled to dividend equivalent units that vest subject to the same vesting requirements or lapse of transfer restrictions, as applicable, as the underlying restricted stock award. The fair value of restricted stock awards is based on our stock price at the grant date. The following table summarizes restricted stock activity for the year ended December 31, 2017 . (Shares and per share amounts in actuals) Number of Shares Weighted Average Grant Date Fair Value Non-vested at December 31, 2016 120,879 $ 6.37 Granted 81,103 10.85 Vested (1) (120,879 ) 6.37 Canceled — — Non-vested at December 31, 2017 (2) 81,103 $ 10.85 _________ (1) The total fair value of shares that vested during the years ended December 31, 2017 , 2016 and 2015 was $0.8 million, $0.8 million and $0.5 million, respectively. (2) As of December 31, 2017 , there was $0.4 million of unrecognized compensation cost related to restricted stock, which is expected to be recognized over a weighted average period of 0.5 years . Restricted Stock Units and Performance Stock Units Restricted stock units (“RSUs”) and performance stock units (“PSUs”) are equity awards granted to employees that entitle the holder to shares of our common stock when the award vests. RSUs may be time-vested over three years or vested at grant but subject to transfer restrictions, while PSUs vest based on corporate performance targets over a three -year period. Outstanding RSUs are entitled to dividend equivalent units that vest subject to the same vesting requirements or lapse of transfer restrictions, as applicable, as the underlying award. The fair value of RSUs is based on our stock price at the grant date. The following table summarizes RSU and PSU activity for the year ended December 31, 2017 . (Shares and per share amounts in actuals) Number of RSUs/ PSUs Weighted Average Grant Date Fair Value Outstanding at December 31, 2016 7,486,610 $ 7.21 Granted 2,247,337 11.79 Vested and converted to common stock (1) (3,765,803 ) 7.75 Canceled (22,854 ) 8.82 Outstanding at December 31, 2017 (2) 5,945,290 $ 8.60 __________ (1) The total fair value of RSUs/PSUs that vested and converted to common stock during the years ended December 31, 2017 , 2016 and 2015 was $29.2 million, $22.2 million and $18.9 million, respectively. (2) As of December 31, 2017 , there was $13.4 million of unrecognized compensation cost related to RSUs/PSUs, which is expected to be recognized over a weighted average period of 1.4 years . Employee Stock Purchase Plan Employees may purchase shares of our common stock at the end of a 12 -month offering period at a price equal to the share price at the beginning of the 12-month period, less 15 percent , up to a maximum purchase price of $7,500 (whole dollars). The purchase price for each offering is determined at the beginning of the offering period on August 1. The fair values of the stock purchase rights of the ESPP offerings were calculated using a Black-Scholes option pricing model with the following weighted average assumptions: Years Ended December 31, (Dollars per share) 2017 2016 2015 Risk-free interest rate 1.22 % 0.50 % 0.33 % Expected volatility 32 % 32 % 27 % Expected dividend rate — % — % — % Expected life of the option 1 year 1 year 1 year Weighted average fair value of stock purchase rights $ 2.36 $ 1.53 $ 1.74 The expected volatility is based on implied volatility from publicly-traded options on our stock at the grant date and historical volatility of our stock consistent with the expected life. The risk-free interest rate is based on the U.S. Treasury bill rate at the grant date consistent with the expected life. The dividend yield is zero , as we have not paid dividends nor do we anticipate paying dividends on our common stock in 2018. The fair values were amortized to compensation cost on a straight-line basis over a one -year vesting period. As of December 31, 2017 , there was $0.3 million of unrecognized compensation cost related to the ESPP, which is expected to be recognized by July 2018. During the year ended December 31, 2017, plan participants purchased 283,952 shares of our common stock. No shares were purchased for the year ended December 31, 2016, as our stock price on July 31, 2016 was less than the offering price for the ESPP plan. During the year ended December 31, 2015, plan participants purchased 163,136 shares of our common stock.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements We use estimates of fair value in applying various accounting standards for the consolidated financial statements. We categorize our fair value estimates based on a hierarchal 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.” 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 December 31, 2017 December 31, 2016 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Available-for-sale investments $ — $ 244,088 $ — $ 244,088 $ — $ 208,603 $ — $ 208,603 Derivative instruments — 812 — 812 — 7,808 — 7,808 Total $ — $ 244,900 $ — $ 244,900 $ — $ 216,411 $ — $ 216,411 Liabilities Derivative instruments $ — $ (2,584 ) $ — $ (2,584 ) $ — $ (25,937 ) $ — $ (25,937 ) Total $ — $ (2,584 ) $ — $ (2,584 ) $ — $ (25,937 ) $ — $ (25,937 ) The following table summarizes the fair values of our financial assets and liabilities, including derivative financial instruments. December 31, 2017 December 31, 2016 Fair Value Carrying Value Difference Fair Value Carrying Value Difference Earning assets Loans held for investment, net $ 20,673,136 $ 18,567,641 $ 2,105,495 $ 16,520,786 $ 15,137,922 $ 1,382,864 Cash and cash equivalents 1,534,339 1,534,339 — 1,918,793 1,918,793 — Available-for-sale investments 244,088 244,088 — 208,603 208,603 — Accrued interest receivable 967,482 967,482 — 766,106 766,106 — Tax indemnification receivable 168,011 168,011 — 259,532 259,532 — Derivative instruments 812 812 — 7,808 7,808 — Total earning assets $ 23,587,868 $ 21,482,373 $ 2,105,495 $ 19,681,628 $ 18,298,764 $ 1,382,864 Interest-bearing liabilities Money-market and savings accounts $ 8,470,209 $ 8,470,209 $ — $ 7,963,925 $ 7,963,925 $ — Certificates of deposit 7,044,208 7,034,121 (10,087 ) 5,510,504 5,471,065 (39,439 ) Short-term borrowings — — — — — — Long-term borrowings 3,299,871 3,275,270 (24,601 ) 2,160,105 2,167,979 7,874 Accrued interest payable 35,363 35,363 — 21,058 21,058 — Derivative instruments 2,584 2,584 — 25,937 25,937 — Total interest-bearing liabilities $ 18,852,235 $ 18,817,547 $ (34,688 ) $ 15,681,529 $ 15,649,964 $ (31,565 ) Excess of net asset fair value over carrying value $ 2,070,807 $ 1,351,299 The methods and assumptions used to estimate the fair value of each class of financial instruments are as follows: Cash and Cash Equivalents Cash and cash equivalents are carried at cost. Carrying value approximated fair value for disclosure purposes. These are level 1 valuations. Investments Investments are classified as available-for-sale and are carried at fair value in the consolidated financial statements. Investments in mortgage-backed securities and Utah Housing Corporation bonds are valued using observable market prices of similar assets. As such, these are level 2 valuations. Loans Held For Investment Our Private Education Loans, FFELP Loans and Personal Loans are accounted for at cost or at the lower of cost or market if the loan is held-for-sale. For both Private Education Loans and FFELP Loans, fair value was determined by modeling expected loan level cash flows using stated terms of the assets and internally developed assumptions to determine aggregate portfolio yield, net present value and average life. The significant assumptions used to determine fair value are prepayment speeds, default rates, cost of funds and required return on equity. Significant inputs into the model are not observable. However, we do calibrate the model based on market transactions when appropriate. As such, these are level 3 valuations. Accrued Interest Receivable Accrued interest receivable is carried at cost. The carrying value approximates fair value due to its short-term nature. This is a level 1 valuation. Tax Indemnification Receivable Tax indemnification receivable is carried at cost. The carrying value approximates fair value. This is a level 2 valuation. Money Market and Savings Accounts The fair value of money market and savings accounts equal the amounts payable on demand at the balance sheet date and are reported at their carrying value. These are level 1 valuations. Certificates of Deposit The fair values of CDs are estimated using discounted cash flows based on rates currently offered for deposits of similar remaining maturities. These are level 2 valuations. Accrued Interest Payable Accrued interest payable is carried at cost. The carrying value approximates fair value due to its short-term nature. This is a level 1 valuation. Borrowings Borrowings are accounted for at cost in the consolidated financial statements. The carrying value of short-term borrowings approximated fair value for disclosure purposes, due to the short-term nature of those borrowings. This is a level 1 valuation. The fair value of long-term borrowings is estimated using current market prices. This is a level 2 valuation. Derivatives All derivatives are accounted for at fair value in the consolidated financial statements. The fair value of derivative financial instruments was determined by a standard derivative pricing and option model using the stated terms of the contracts and observable market inputs. It is our policy to compare the derivative fair values to those received from our counterparties in order to evaluate the model’s outputs. When determining the fair value of derivatives, we take into account counterparty credit risk for positions where we are exposed to the counterparty on a net basis by assessing exposure net of collateral held. When the counterparty has exposure to us under derivative contracts with the Company, we fully collateralize the exposure (subject to certain thresholds). Interest rate swaps are valued using a standard derivative cash flow model with a LIBOR swap yield curve, which is an observable input from an active market. These derivatives are level 2 fair value estimates in the hierarchy. The carrying value of borrowings designated as the hedged item in a fair value hedge is adjusted for changes in fair value due to changes in the benchmark interest rate (one-month LIBOR). These valuations are determined through standard pricing models using the stated terms of the borrowings and observable yield curves.

Arrangements with Navient Corpo

Arrangements with Navient Corporation	12 Months Ended
	Dec. 31, 2017
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 with Navient (the “Separation and Distribution Agreement”). We also entered into various other ancillary agreements with Navient to effect the Spin-Off and provide a framework for our relationship with Navient thereafter, such as a transition services agreement, a tax sharing agreement, an employee matters agreement, a loan servicing and administration agreement, a joint marketing agreement, a key services agreement, a data sharing agreement and a master sublease agreement. The majority of these agreements are transitional in nature with most having terms that have expired or will expire within the next one to two years . We continue to have exposure to risks related to Navient’s creditworthiness. If we are unable to obtain indemnification payments from Navient, our results of operations and financial condition could be materially and adversely affected. Pursuant to the terms of the Spin-Off and applicable law, Navient assumed responsibility for all liabilities (whether accrued, contingent or otherwise and whether known or unknown) arising out of or resulting from the conduct of pre-Spin-Off SLM and its subsidiaries’ businesses prior to the Spin-Off, other than certain specifically identified liabilities relating to the conduct of our consumer banking business. Nonetheless, given the prior usage of the Sallie Mae and SLM names by entities now owned by Navient, we and our subsidiaries may from time to time be improperly named as defendants in legal proceedings where the allegations at issue are the legal responsibility of Navient. Most of these legal proceedings involve matters that arose in whole or in part in the ordinary course of business of pre-Spin-Off SLM. Likewise, as the period of time since the Spin-Off increases, so does the likelihood any allegations that may be made may be in part for our own actions in a post-Spin-Off time period and in part for Navient’s conduct in a pre-Spin-Off time period. We will not be providing information on these proceedings unless there are material issues of fact or disagreement with Navient as to the bases of the proceedings or responsibility therefor that we believe could have a material, adverse impact on our business, assets, financial condition, liquidity or outlook if not resolved in our favor. We briefly summarize below some of the most significant agreements and relationships we continue to have with Navient. For additional information regarding the Separation and Distribution Agreement and the other ancillary agreements, see our Current Report on Form 8-K filed on May 2, 2014. Separation and Distribution Agreement The Separation and Distribution Agreement addresses, among other things, the following ongoing activities: • the obligation of each party to indemnify the other against liabilities retained or assumed by that party pursuant to the Separation and Distribution Agreement and in connection with claims of third-parties; • the allocation among the parties of rights and obligations under insurance policies; • the agreement by us and Navient (i) not to engage in certain competitive business activities for a period of five years , (ii) as to the effect of the non-competition provisions on post-spin merger and acquisition activities of the parties and (iii) regarding “first look” opportunities; and • the creation of a governance structure, including a separation oversight committee of representatives from us and Navient, by which matters related to the separation and other transactions contemplated by the Separation and Distribution Agreement will be monitored and managed. The Separation and Distribution Agreement provides specific processes and procedures pursuant to which we may submit claims for indemnification to Navient and, to date, Navient has acknowledged and accepted substantially all claims that we have submitted. Nonetheless, if for any reason Navient is unable or unwilling to pay claims made against it, our costs, operating expenses, cash flows and financial condition could be materially and adversely affected over time. 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 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 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. • At the time of this filing, the Bank remains subject to a Consent Order (the “DOJ Consent Order”) issued by the Department of Justice (the “DOJ”). Under the terms of the Separation and Distribution Agreement, 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. • 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 December 31, 2017 was $35 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 December 31, 2017, the remaining balance of the indemnification receivable related to those uncertain tax positions was $ 25 million. In addition, we believe we are indemnified by Navient for uncertain 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. The remaining balance of the indemnification receivable related to these uncertain tax positions was $108 million at December 31, 2017. See Note 2, “Significant Accounting Policies — Income Taxes,” for additional details. Long-Term Arrangements The loan servicing and administration agreement governs the terms by which Navient provides servicing, administration and collection services for the Bank’s portfolio of FFELP Loans and $48 million of Private Education Loans, as well as servicing history information with respect to Private Education Loans previously serviced by Navient and access to certain promissory notes in Navient’s possession. The loan servicing and administration agreement has a fixed term with a renewal option in favor of the Bank. The data sharing agreement states we will continue to have the right to obtain from Navient certain post-Spin-Off performance data relating to Private Education Loans owned or serviced by Navient to support and facilitate ongoing underwriting, originations, forecasting, performance and reserve analyses. The tax sharing agreement governs the respective rights, responsibilities and obligations of us and Navient after the Spin-Off relating to taxes, including with respect to the payment of taxes, the preparation and filing of tax returns and the conduct of tax contests. Under this agreement, each party is generally liable for taxes attributable to its business. The agreement also addresses the allocation of tax liabilities that are incurred as a result of the Spin-Off and related transactions. Additionally, the agreement restricts the parties from taking certain actions that could prevent the Spin-Off from qualifying for the anticipated tax treatment. 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 this agreement. This agreement predates the Spin-Off, but was significantly amended and reduced in scope in connection with the Spin-Off. Post-Spin-Off, the Bank retains 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. At December 31, 2017, we held approximately $48 million of Split Loans. During the year ended December 31, 2017, the Bank sold loans to the Purchasers in the amount of $ 12.0 million in principal and $ 0.3 million in accrued interest income. During the year ended December 31, 2016, the Bank sold loans to the Purchasers in the amount of $15.7 million in principal and $0.3 million in accrued interest income. During the year ended December 31, 2015, the Bank sold loans to the Purchasers in the amount of $27.0 million in principal and $0.6 million in accrued interest income. There was no gain or loss resulting from loans sold to the Purchasers in the year ended December 31, 2017, 2016 and 2015, respectively. Total write-downs to fair value for loans sold to the Purchasers with a fair value lower than par totaled $ 5.0 million, $6.0 million and $7.6 million in the years ended December 31, 2017, 2016 and 2015, respectively. Navient is the servicer for all of these loans.

Regulatory Capital

Regulatory Capital	12 Months Ended
	Dec. 31, 2017
Banking and Thrift [Abstract]
Regulatory Capital	Regulatory Capital The Bank is subject to various regulatory capital requirements administered by the FDIC and 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 operations 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 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 % As of December 31, 2016: Common Equity Tier 1 Capital (to Risk-Weighted Assets) $ 2,011,583 12.6 % $ 1,038,638 > 6.5 % Tier 1 Capital (to Risk-Weighted Assets) $ 2,011,583 12.6 % $ 1,278,323 > 8.0 % Total Capital (to Risk-Weighted Assets) $ 2,197,997 13.8 % $ 1,597,904 > 10.0 % Tier 1 Capital (to Average Assets) $ 2,011,583 11.1 % $ 907,565 > 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 on its common stock for the years ended December 31, 2017 , 2016 and 2015, respectively. For the foreseeable future, we expect the Bank to only pay dividends to the Company as may be necessary to provide for regularly scheduled dividends payable on the Company’s Series B Preferred Stock.

Defined Contribution Plans

Defined Contribution Plans	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Defined Contribution Plans	Defined Contribution Plans We participate in a defined contribution plan which is intended to qualify under section 401(k) of the Internal Revenue Code. The Sallie Mae 401(k) Savings Plan covers substantially all employees. After six months of service, we match 100 percent of the first three percent of contributions and match 50 percent of the next two percent of contributions for eligible employees. After one month of service, eligible employees receive a one percent core employer contribution. For the years ended December 31, 2017 , 2016 and 2015 , we contributed $ 5.0 million, $ 4.4 million and $3.8 million, respectively, to this plan.

Commitments, Contingencies and

Commitments, Contingencies and Guarantees	12 Months Ended
	Dec. 31, 2017
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 December 31, 2017 , we had $ 1.8 billion of outstanding contractual loan commitments which we expect to fund during the remainder of the 2017/2018 academic year. At December 31, 2017 , we had a $1.9 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 settlements with (a) the FDIC regarding disclosures and assessments of certain late fees, as well as compliance with the Servicemembers Civil Relief Act (the “SCRA”), and (b) the DOJ regarding compliance with the SCRA. In connection with the settlements, the Bank became subject to a Consent Order, Order to Pay Restitution, and Order to Pay Civil Money Penalty dated May 13, 2014 issued by the FDIC (the “FDIC Consent Order”) and the DOJ Consent Order, which was approved by the U.S. District Court for the District of Delaware on September 29, 2014. Under the terms of the Separation and Distribution Agreement, Navient is responsible for funding all liabilities under the regulatory orders 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. On March 27, 2017, the Bank received confirmation from the FDIC that effective March 23, 2017, the FDIC terminated the FDIC Consent Order. The termination was issued with no conditions. The Bank continues to be in full compliance with the DOJ Consent Order, including policy and procedure updates. Pursuant to the terms of the DOJ Consent Order, the Bank will remain subject to certain DOJ reporting and record-keeping requirements until September 29, 2018. In May 2014, the Bank received a Civil Investigative Demand (“CID”) from 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 lawsuit 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 separate 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. Following argument on the Bank’s motion on July 18, 2017, the Illinois court took the Bank’s motion under advisement. As of the date of this report, the court has not ruled on the Bank’s motion. 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. To date, two other state attorneys general (Washington and Pennsylvania) have filed suits against Navient and one or more of its current subsidiaries related to matters arising from the Multi-State Investigation. Neither SLM, the Bank, nor any of their current subsidiaries are named in, or otherwise a party to, the Washington or Pennsylvania lawsuits, and no claims are asserted against them. Each complaint asserts in its own fashion that Navient assumed responsibility for these matters under the Separation and Distribution Agreement for the alleged conduct in the complaints. 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 damage 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. Based on current knowledge, management does not believe there are loss contingencies, if any, arising from pending investigations, litigation or regulatory matters for which reserves should be established.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Reconciliations of the statutory U.S. federal income tax rates to our effective tax rate for continuing operations follow: Years Ended December 31, 2017 2016 2015 Statutory rate 35.0 % 35.0 % 35.0 % Tax reform 3.1 — — State tax, net of federal benefit 2.6 3.1 3.0 Reverse federal impact of indemnification adjustments 2.5 (0.7 ) 0.1 Unrecognized tax benefits, U.S. federal and state, net of federal benefit (2.0 ) 1.6 (0.5 ) Excess tax benefits/deficiencies for employee stock-based compensation, federal and state, net of federal benefit (1.7 ) — — Impact of state rate change on net deferred tax liabilities, net of federal benefit 0.6 (0.5 ) 0.5 State, valuation allowance adjustments on net operating losses 0.2 1.0 (0.2 ) Other, net 0.9 0.1 (0.4 ) Effective tax rate 41.2 % 39.6 % 37.5 % The effective tax rate varies from the statutory U.S. federal rate of 35 percent primarily due to the impact of tax reform and the impact of state taxes, net of federal benefit, for the year ended December 31, 2017 , and due to the impact of state taxes, net of federal benefit, for the years ended December 31, 2016 and 2015 . Income tax expense consists of: December 31, 2017 2016 2015 Current provision: Federal $ 248,191 $ 228,505 $ 215,950 State 13,092 24,336 26,057 Total current provision 261,283 252,841 242,007 Deferred (benefit)/provision: Federal (58,124 ) (89,518 ) (69,546 ) State (628 ) 786 (7,681 ) Total deferred benefit (58,752 ) (88,732 ) (77,227 ) Provision for income tax expense $ 202,531 $ 164,109 $ 164,780 The tax effect of temporary differences that give rise to deferred tax assets and liabilities is summarized below. The December 31, 2016 amounts were based upon a 35 percent statutory U.S. federal income tax rate, and the December 31, 2017 amounts were based upon a 21 percent statutory U.S. federal income tax rate. December 31, 2017 2016 Deferred tax assets: Loan reserves $ 62,603 $ 72,125 Stock-based compensation plans 10,216 16,471 Deferred revenue 782 793 Operating loss carryovers 4,186 8,371 Unrealized losses — 5,364 Accrued expenses not currently deductible 5,356 13,605 Unrecorded tax benefits 3,781 5,702 Other 2,410 10,844 Total deferred tax assets 89,334 133,275 Deferred tax liabilities: Gains on repurchased debt 40,175 126,403 Fixed assets 5,303 6,831 Acquired intangible assets 4,595 6,288 Unrealized gains 1,104 — Federal deferred for state receivable 3,584 2,058 Other 1,349 875 Total deferred tax liabilities 56,110 142,455 Net deferred tax liabilities $ 33,224 $ (9,180 ) Included in operating loss carryovers is a valuation allowance of $ 68.6 million and $ 88.4 million as of December 31, 2017 and 2016, respectively, against a portion of our state net operating loss carryovers that management believes is more likely than not to expire prior to being realized. The ultimate realization of the deferred tax assets is dependent upon the generation of future taxable income of the appropriate character (i.e., capital or ordinary) during the period in which the temporary differences become deductible. Management considers, among other things, the scheduled reversals of deferred tax liabilities and the history of positive taxable income in evaluating the realizability of the deferred tax assets. Management believes that it is more likely than not that the results of future operations will generate sufficient taxable income to realize our deferred tax assets (other than state net operating loss carryovers as outlined above). As of December 31, 2017 , we have apportioned state net operating loss carryforwards of $5.3 million which begin to expire in 2029. Accounting for Uncertainty in Income Taxes The following table summarizes changes in unrecognized tax benefits: December 31, 2017 2016 2015 Unrecognized tax benefits at beginning of year $ 152,581 $ 47,109 $ 59,405 Increases resulting from tax positions taken during a prior period 7,482 110,894 3,456 Decreases resulting from tax positions taken during a prior period (7,025 ) (3,285 ) (10,121 ) Increases resulting from tax positions taken during the current period 1,656 817 3,447 Decreases related to settlements with taxing authorities (3,594 ) (123 ) (7,481 ) Reductions related to the lapse of statute of limitations (19,492 ) (2,831 ) (1,597 ) Unrecognized tax benefits at end of year $ 131,608 $ 152,581 $ 47,109 As of December 31, 2017 , the gross unrecognized tax benefits are $131.6 million. Included in the $131.6 million are $128.2 million of unrecognized tax benefits that, if recognized, would favorably impact the effective tax rate. As a part of the Spin-Off, the Company recorded a liability related to uncertain tax positions for which it is indemnified by Navient. In addition, we believe we are indemnified by Navient for uncertain 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. See Note 2, “Significant Accounting Policies — Income Taxes,” for additional details. Tax related interest and penalty expense is reported as a component of income tax expense. As of December 31, 2017 , 2016 and 2015, the total amount of income tax-related accrued interest and penalties, net of related benefit, recognized in the consolidated balance sheets was $ 21.2 million, $ 20.2 million and $ 7.0 million, respectively. For the years ended December 31, 2017 , 2016 and 2015 , the total amount of income tax-related accrued interest, net of related tax benefit, recognized in the consolidated statements of income was $ 2.7 million, $ 5.1 million and $ 1.4 million, respectively. The Company or one of its subsidiaries files income tax returns at the U.S. federal level and in most U.S. states. U.S. federal income tax returns filed for years 2013 and prior are no longer subject to examination. Various combinations of subsidiaries, tax years, and jurisdictions remain open for review, subject to statute of limitations periods (typically 3 to 4 prior years). We do not expect the resolution of open audits to have a material impact on our unrecognized tax benefits. It is reasonably possible that the uncertain tax position reserve may decrease by as much as $ 86.2 million during the next 12 months due to the expiration of statutes of limitations primarily related to indemnified tax liabilities. The reduction in the uncertain tax position reserve would be reflected as a tax benefit. We recorded a tax indemnification receivable from Navient for the indemnified tax liabilities which are included in the uncertain tax position reserve. The tax benefit will be offset by an expense related to the write-down of the indemnification receivable.

Concentrations of Risk

Concentrations of Risk	12 Months Ended
	Dec. 31, 2017
Risks and Uncertainties [Abstract]
Concentrations of Risk	Concentrations of Risk Our business is primarily focused on helping students and their families save, plan and pay for college. We primarily originate, service and/or collect loans made to students and their families to finance the cost of their education. We provide funding, delivery and servicing support for education loans in the United States through our Private Education Loan program. Because of this concentration in one industry, we are exposed to credit, legislative, operational, regulatory, and liquidity risks associated with the student loan industry. Concentration Risk in the Revenues Associated with Private Education Loans We compete in the Private Education Loan market with banks and other consumer lending institutions, some with strong consumer brand name recognition and greater financial resources. We compete based on our products, origination capability and customer service. To the extent our competitors compete aggressively or more effectively, we could lose market share to them or subject our existing loans to refinancing risk. Our product offerings may not prove to be profitable and may result in higher than expected losses. We are a leading provider of saving- and paying-for-college products and programs. This concentration gives us a competitive advantage in the marketplace. This concentration also creates risks in our business, particularly in light of our concentrations as a Private Education Loan lender. If population demographics result in a decrease in college-age individuals, if demand for higher education decreases, if the cost of attendance of higher education decreases, if public resistance to higher education costs strengthens, or if the demand for higher education loans decreases, our consumer lending business could be negatively affected. In addition, the federal government, through the Federal Direct Student Loan Program (the “DSLP”), poses significant competition to our private credit loan products. If loan limits under the DSLP increase, DSLP loans could be more widely available to students and their families and DSLP loans could increase, resulting in further decreases in the size of the Private Education Loan market and demand for our Private Education Loan products.

Parent Only Statements

Parent Only Statements	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Parent Only Statements	Parent Only Statements The following parent company-only financial information should be read in conjunction with the other notes to the consolidated financial statements. The accounting policies for the parent company-only financial statements are the same as those used in the presentation of the consolidated financial statements other than the parent company-only financial statements account for the parent company’s investments in its subsidiaries under the equity method. Parent Only Condensed Balance Sheets December 31, 2017 2016 Assets Cash and cash equivalents $ 260,255 $ 292,277 Total investments in subsidiaries (primarily Sallie Mae Bank) 2,401,114 2,042,015 Tax indemnification receivable 168,011 259,532 Due from subsidiaries, net 37,521 31,834 Other assets 1,279 1,561 Total assets $ 2,868,180 $ 2,627,219 Liabilities and Equity Liabilities Long-term borrowings $ 196,539 $ — Income taxes payable, net 159,954 256,556 Payable due to Navient 10,575 2,823 Other liabilities 26,856 20,782 Total liabilities 393,924 280,161 Equity Preferred stock, par value $0.20 per share, 20 million shares authorized: Series A: 0 and 3.3 million shares issued, respectively, at stated value of $50 per share — 165,000 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: 443.5 million and 436.6 million shares issued, respectively 88,693 87,327 Additional paid-in capital 1,222,277 1,175,564 Accumulated other comprehensive income (loss) (net of tax expense (benefit) of $1,696 and ($5,364), respectively) 2,748 (8,671 ) Retained earnings 868,182 595,322 Total SLM Corporation stockholders’ equity before treasury stock 2,581,900 2,414,542 Less: Common stock held in treasury at cost: 11.1 million and 7.7 million shares, respectively (107,644 ) (67,484 ) Total equity 2,474,256 2,347,058 Total liabilities and equity $ 2,868,180 $ 2,627,219 Parent Only Condensed Statements of Income Years Ended December 31, 2017 2016 2015 Interest income $ 5,497 $ 5,367 $ 6,414 Interest expense 8,170 — — Net interest income (2,673 ) 5,367 6,414 Non-interest income (loss) (33,956 ) 9,396 (239 ) Non-interest expenses 35,810 32,553 36,141 Loss before income tax benefit and equity in net income from subsidiaries (72,439 ) (17,790 ) (29,966 ) Income tax benefit (40,598 ) (2,839 ) (8,612 ) Equity in net income from subsidiaries (primarily Sallie Mae Bank) 320,775 265,278 295,638 Net income 288,934 250,327 274,284 Preferred stock dividends 15,714 21,204 19,595 Net income attributable to SLM Corporation common stock $ 273,220 $ 229,123 $ 254,689 Parent Only Condensed Statements of Cash Flows Years Ended December 31, 2017 2016 2015 Cash flows from operating activities: Net income $ 288,934 $ 250,327 $ 274,284 Adjustments to reconcile net income to net cash provided by (used in) operating activities: Undistributed earnings of subsidiaries (320,775 ) (265,278 ) (295,638 ) Loss (income) on tax indemnification receivable 31,888 (12,283 ) (5,398 ) Amortization of unsecured debt upfront fees 596 — — Decrease (increase) in investment in subsidiaries, net 1,158 63,222 (103,602 ) Decrease in tax indemnification receivable 59,633 59,633 59,633 (Increase) decrease in due from subsidiaries, net (5,687 ) (10,438 ) 11,012 Increase in other assets (24,627 ) (8,972 ) (14,366 ) Decrease in income taxes payable, net (87,983 ) (54,175 ) (53,167 ) (Decrease) increase in payable due to entity that is a subsidiary of Navient (593 ) 553 (6,774 ) Increase in other liabilities 10,205 8,856 1,402 Total adjustments (336,185 ) (218,882 ) (406,898 ) Net cash (used in) provided by operating activities (47,251 ) 31,445 (132,614 ) Cash flows from investing activities: Net cash provided by (used in) investing activities — — — Cash flows from financing activities: Unsecured debt issued 197,000 — — Issuance costs for unsecured debt offering (1,057 ) — — Redemption of Series A Preferred Stock (165,000 ) — — Preferred stock dividends paid (15,714 ) (21,204 ) (19,595 ) Net cash provided by (used in) financing activities 15,229 (21,204 ) (19,595 ) Net (decrease) increase in cash and cash equivalents (32,022 ) 10,241 (152,209 ) Cash and cash equivalents at beginning of year 292,277 282,036 434,245 Cash and cash equivalents at end of year $ 260,255 $ 292,277 $ 282,036

Selected Quarterly Financial In

Selected Quarterly Financial Information (unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Information (unaudited)	Selected Quarterly Financial Information (unaudited) 2017 First Second Third Fourth (Dollars in thousands, except per share data) Quarter Quarter Quarter Quarter Net interest income $ 268,076 $ 269,893 $ 282,061 $ 309,191 Less: provisions for credit losses 25,296 50,215 54,930 55,324 Net interest income after provisions for credit losses 242,780 219,678 227,131 253,867 (Losses) gains on derivative and hedging activities, net (5,378 ) (3,609 ) 1,661 (940 ) Other income (loss) 11,346 10,629 4,455 (21,066 ) Total operating expenses 102,677 111,251 116,142 118,550 Acquired intangible asset amortization expense 117 117 117 118 Income tax expense 51,011 44,713 40,617 66,190 Net income 94,943 70,617 76,371 47,003 Preferred stock dividends 5,575 3,974 3,028 3,137 Net income attributable to SLM Corporation common stock $ 89,368 $ 66,643 $ 73,343 $ 43,866 Basic earnings per common share attributable to SLM Corporation (1) $ 0.21 $ 0.15 $ 0.17 $ 0.10 Diluted earnings per common share attributable to SLM Corporation (1) $ 0.20 $ 0.15 $ 0.17 $ 0.10 _____ (1) Basic and diluted earnings per common share attributable to SLM Corporation are computed independently for each of the quarters presented. Therefore, the sum of quarterly basic and diluted earnings per common share information may not equal annual basic and diluted earnings per common share. 2016 First Second Third Fourth (Dollars in thousands, except per share data) Quarter Quarter Quarter Quarter Net interest income $ 209,863 $ 212,766 $ 223,275 $ 245,434 Less: provisions for credit losses 32,602 41,793 41,784 43,226 Net interest income after provisions for credit losses 177,261 170,973 181,491 202,208 Gains on sales of loans, net — — — 230 (Losses) gains on derivative and hedging activities, net (354 ) 2,142 1,368 (4,114 ) Other income 21,028 13,683 21,598 13,235 Total operating expenses 92,885 94,777 99,709 98,036 Acquired intangible asset amortization expense 260 261 226 159 Income tax expense 38,875 34,555 47,557 43,122 Net income 65,915 57,205 56,965 70,242 Preferred stock dividends 5,139 5,243 5,316 5,506 Net income attributable to SLM Corporation common stock $ 60,776 $ 51,962 $ 51,649 $ 64,736 Basic earnings per common share attributable to SLM Corporation (1) $ 0.14 $ 0.12 $ 0.12 $ 0.15 Diluted earnings per common share attributable to SLM Corporation (1) $ 0.14 $ 0.12 $ 0.12 $ 0.15 _____ (1) Basic and diluted earnings per common share attributable to SLM Corporation are computed independently for each of the quarters presented. Therefore, the sum of quarterly basic and diluted earnings per common share information may not equal annual basic and diluted earnings per common share.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Amendment to the ABCP Facility On February 21, 2018, we amended and extended the maturity of the ABCP Facility, discussed in Note 9, “Borrowings.” The amended ABCP Facility is a $750 million ABCP Facility, under which the full $750 million is available for us to draw. 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).

Significant Accounting Polici33

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Use of Estimates and Assumptions	Use of Estimates and Assumptions The financial reporting and accounting policies of SLM Corporation conform to generally accepted accounting principles in the United States of America (“GAAP”). The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Key accounting policies that include significant judgments and estimates include the valuation of allowance for loan losses, fair value measurements and derivative accounting.
Consolidation	Consolidation 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. 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.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include cash held in the Federal Reserve Bank of San Francisco (the “FRB”) and commercial bank accounts, and other short-term liquid instruments with original maturities of three months or less. Fees associated with investing cash and cash equivalents are amortized into interest income using the effective interest rate method.
Investments	Investments Investments consisted of mortgage-backed securities and Utah Housing Corporation bonds. We record our investment purchases and sales on a trade date basis. The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts, which are amortized using the effective interest rate method. Our investments are classified as available-for-sale and reported at fair value. Unrealized gains or losses on available-for-sale investments are recorded in equity and are reported as a component of other comprehensive income (loss), net of applicable income taxes, unless a decline in the investment’s value is considered to be other-than-temporary, in which case the loss is recorded directly to earnings. Management reviews all investments at least quarterly to determine whether any impairment is other-than-temporary. Impairment is evaluated by considering several factors, including the length of time and extent to which the fair value has been less than cost, the financial condition and near-term prospects of the issuer, and the intent and ability to retain the investment to allow for an anticipated recovery in fair value. If, based on the analysis, it is determined that the impairment is other-than-temporary, the investment is written down to fair value and a loss is recognized through earnings.
Loans Held for Investment	Loans Held for Investment Loans, consisting primarily of Private Education Loans and FFELP Loans, that we have the ability and intent to hold for the foreseeable future are classified as held for investment, and are carried at amortized cost. Amortized cost includes the unamortized premiums, discounts, and capitalized origination costs and fees, all of which are amortized to interest income as discussed under “Loan Interest Income.” Loans which are held for investment are reported net of an allowance for loan losses.
Restricted Cash and Investments	Restricted Cash and Investments Restricted cash and investments primarily include amounts held in student loan securitization trusts and other secured borrowings. This cash must be used to make payments related to trust obligations. Amounts on deposit in these accounts are primarily the result of timing differences between when principal and interest is collected on the trust assets and when principal and interest is paid on trust liabilities.
Allowance for Loan Losses	Allowance for Loan Losses We maintain an allowance for loan losses at an amount sufficient to absorb probable losses incurred in our portfolios, as well as regarding future loan commitments, at the reporting date based on a projection of estimated probable credit losses incurred in the portfolio. We consider a loan to be impaired when, based on current information, a loss has been incurred and it is probable that we will not receive all contractual amounts due. When making our assessment as to whether a loan is impaired, we also take into account more than insignificant delays in payment. We generally evaluate impaired loans on an aggregate basis by grouping similar loans. We analyze our portfolios to determine the effects that the various stages of delinquency and forbearance have on borrower default behavior and ultimate charge off. We estimate the allowance for loan losses for our loan portfolios using a roll rate analysis of delinquent and current accounts. A “roll rate analysis” is a technique used to estimate the likelihood that a loan receivable may progress through the various delinquency stages and ultimately charge off. We also take into account the current and future economic environment and certain other qualitative factors when calculating the allowance for loan losses. The evaluation of the allowance for loan losses is inherently subjective, as it requires material estimates that may be susceptible to significant changes. Our default estimates are based on a loss emergence period of one year for Private Education Loans and two years for FFELP Loans. A loss emergence period represents the expected period between the first occurrence of an event likely to cause a loss on a loan and the date the loan is expected to be charged off, taking into consideration account management practices that affect the timing of a loss, such as the usage of forbearance. The loss emergence period underlying the allowance for loan losses is subject to a number of assumptions. If actual future performance in delinquency, charge-offs and recoveries is significantly different than estimated, or account management assumptions or practices were to change, this could materially affect the estimate of the allowance for loan losses, the timing of when losses are recognized, and the related provision for credit losses on our consolidated statements of income.
Allowance for Private Education Loan Losses	Allowance for Private Education Loan Losses We maintain an allowance for loan losses at an amount sufficient to absorb probable losses incurred in our portfolios at the reporting date based on a projection of estimated probable credit losses incurred in the portfolio. In determining the allowance for loan losses on our Private Education Loans that are not troubled debt restructurings (“TDRs”), we estimate the principal amount of loans that will default over the next year ( one year being the expected period between a loss event and default) using a roll rate model and how much we expect to recover over the same one -year period related to the defaulted amount. The expected defaults less our expected recoveries adjusted for any qualitative factors (discussed below) equal the allowance related to this portfolio. Our historical experience indicates that, on average, the time between the date that a customer experiences a default causing event (i.e., the loss trigger event) and the date that we charge off the unrecoverable portion of that loan is one year. In estimating both the non-TDR and TDR allowance amounts, we start with historical experience of customer delinquency and default behavior. We make judgments about which historical period to start with and then make further judgments about whether that historical experience is representative of future expectations and whether additional adjustments may be needed to those historical default rates. We also take certain other qualitative factors into consideration when calculating the allowance for loan losses. These qualitative factors include, but are not limited to, changes in the economic environment, changes in lending policies and procedures, including changes in underwriting standards and collection, charge-off and recovery practices not already included in the analysis, and the effect of other external factors such as legal and regulatory requirements on the level of estimated credit losses. Our non-TDR allowance for loan losses is estimated using an analysis of delinquent and current accounts. Our roll rate model is used to estimate the likelihood that a loan receivable may progress through the various delinquency stages and ultimately charge off. Once a charge-off forecast is estimated, a recovery assumption is layered on top. In estimating recoveries, we use both estimates of what we would receive from the sale of defaulted loans as well as historical borrower payment behavior to estimate the timing and amount of future recoveries on charged-off loans. The roll rate analysis model is based upon actual experience using the 120 day charge-off default aversion strategies. Once the quantitative calculation is performed, we review the adequacy of the allowance for loan losses and determine if qualitative adjustments need to be considered. In the fourth quarter of 2015, we stopped our previous practice of selling all defaulted loans to third-parties and began collecting on some defaulted loans in-house. It is our expectation that in the future we will continue to collect on defaulted loans in-house as well as sell defaulted loans to third-parties. Prior to this change in practice, we only used estimates of what we would receive from the sale of delinquent loans in estimating recoveries. For December 31, 2017 and 2016, we used both an estimate of recovery rates from in-house collections as well as expectations of future sales of defaulted loans to estimate the timing and amount of future recoveries on charged-off loans. In connection with the Spin-Off, the agreement under which the Bank previously made sales of defaulted loans to an affiliate was amended so that the Bank now has the right to require Navient to purchase (at fair value) loans only where (a) the borrower has a lending relationship with both the Bank and Navient (“Split Loans”) and (b) 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. At December 31, 2017, we held approximately $48 million of Split Loans. Allowance for Personal Loans In December 2016, we began to acquire newly-originated personal loans (“Personal Loans”). We maintain an allowance for loan losses at an amount sufficient to absorb probable losses incurred in this portfolio at the reporting date based on a projection of estimated probable credit losses incurred in the portfolio. In determining the allowance for loan losses on our Personal Loan portfolio that are not TDRs, we estimate the principal amount of the loans that will default over the next twelve months (twelve months being the expected period between a loss event and default) and how much we expect to recover over the same twelve-month period related to the defaulted amounts. The expected defaults less our expected recoveries adjusted for any qualitative factors equal the allowance related to this portfolio. At December 31, 2017, and 2016, we held $ 393.7 million and $ 12.8 million, respectively, in Personal Loans, net of allowance. At December 31, 2017, there were no Personal Loans classified as TDRs. Troubled Debt Restructurings Separately, for our TDR portfolio, we estimate an allowance amount sufficient to cover life-of-loan expected losses through an impairment calculation based on the difference between the loan’s basis and the present value of expected future cash flows (which would include life-of-loan default and recovery assumptions) discounted at the loan’s original effective interest rate. Our TDR portfolio is comprised mostly of loans with interest rate reductions and loans with forbearance usage greater than three months , as further described below. We modify the terms of loans for certain borrowers when we believe such modifications may increase the ability and willingness of a borrower to make payments and thus increase the ultimate overall amount collected on a loan. These modifications generally take the form of a forbearance, a temporary interest rate reduction or an extended repayment plan. Until the fourth quarter of 2017, we generally considered a loan that was in full principal and interest repayment status which had received more than three months of forbearance in a 24 -month period to be a TDR; however, during the first nine months after a loan had entered full principal and interest repayment status, we did not count up to the first six months of forbearance received during that period against the three-month policy limit. Beginning in the fourth quarter of 2017, we revised the policy described above for identifying when a loan should be classified as a TDR due to forbearance. Historically, all loans receiving forbearance under the thresholds described above were classified as TDRs. However, with the refinement, those loans with a FICO score above a certain threshold (based on the most recent quarterly FICO score refresh) that are granted a forbearance will not be classified as TDRs, while loans with a FICO score under the threshold (based on the most recent quarterly FICO score refresh) that are granted a forbearance will be classified as TDRs, once they reach our policy limit for forbearances described above (i.e., more than three months in a 24-month period, subject to the exceptions described for the first nine months after a loan enters full principal and interest repayment status).This change in our determination of when loans should be classified as TDRs does not affect any of our existing loans classified as TDRs and it does not change any of the existing thresholds regarding length of forbearance for becoming a TDR. Instead, it is an additional filter in the TDR analysis that is applied after the loan has met the requisite number of months in forbearance. This change was adopted prospectively beginning in the fourth quarter of 2017 and had an immaterial effect on the allowance for loan losses and provision for loan losses. A loan also becomes a TDR when it is modified to reduce the interest rate on the loan (regardless of when such modification occurs and/or whether such interest rate reduction is temporary). 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. Once a loan qualifies for TDR status, it remains a TDR for allowance purposes for the remainder of its life. As of December 31, 2017 and 2016, approximately 66 percent and 69 percent, respectively, of TDRs were classified as such due to their forbearance status. Key Credit Quality Indicators We determine the collectability of our Private Education Loan portfolio by evaluating certain risk characteristics. We consider credit score, existence of a cosigner, loan status and loan seasoning as the key credit quality indicators because they have the most significant effect on the determination of the adequacy of our allowance for loan losses. Credit scores are an indicator of the creditworthiness of borrowers and the higher the credit scores the more likely it is the borrowers will be able to make all of their contractual payments. Loan status affects the credit risk because a past due loan is more likely to result in a credit loss than a current loan. Additionally, loans in the deferred payment status have different credit risk profiles compared with those in current pay status. Loan seasoning affects credit risk because a loan with a history of making payments generally has a lower incidence of default than a loan with a history of making infrequent or no payments. The existence of a cosigner lowers the likelihood of default as well. We monitor and update these credit quality indicators in the analysis of the adequacy of our allowance for loan losses on a quarterly basis. For Personal Loans, we consider FICO scores at origination and seasoning to be our key credit quality indicators for the same reasons discussed above. Certain Private Education Loans do not require borrowers to begin repayment until six months after they have graduated or otherwise left school. Consequently, the loss estimates for these loans is generally low while the borrower is in school. At December 31, 2017 and 2016, 27 percent and 29 percent , respectively, of the principal balance in the Private Education Loan portfolio was related to borrowers who are in an in-school (fully deferred), grace, or deferment status and not required to make payments. As this population of borrowers leaves school, they will be required to begin payments on their loans, and the allowance for losses may change accordingly. Similar to the rules governing FFELP payment requirements, our collection policies allow for periods of nonpayment for borrowers requesting additional payment grace periods upon leaving school or experiencing temporary difficulty meeting payment obligations. This is referred to as forbearance status and is considered separately in the allowance for loan losses. The loss emergence period is in alignment with the typical collection cycle and takes into account these periods of nonpayment. As part of concluding on the adequacy of the allowance for loan losses, we review key allowance and loan metrics. The most relevant of these metrics considered are the allowance coverage of net charge-offs ratio; the allowance as a percentage of ending total loans and of ending loans in repayment; and delinquency and forbearance percentages. We consider a loan to be delinquent 31 days after the last payment was contractually due. We use a model to estimate the amount of uncollectible accrued interest on Private Education Loans and reserve for that amount against current period interest income.
Allowance for Personal Loans	Allowance for Personal Loans In December 2016, we began to acquire newly-originated personal loans (“Personal Loans”). We maintain an allowance for loan losses at an amount sufficient to absorb probable losses incurred in this portfolio at the reporting date based on a projection of estimated probable credit losses incurred in the portfolio. In determining the allowance for loan losses on our Personal Loan portfolio that are not TDRs, we estimate the principal amount of the loans that will default over the next twelve months (twelve months being the expected period between a loss event and default) and how much we expect to recover over the same twelve-month period related to the defaulted amounts. The expected defaults less our expected recoveries adjusted for any qualitative factors equal the allowance related to this portfolio.
Allowance for FFELP Loan Losses	Allowance for FFELP Loan Losses 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 default claims. For loans disbursed after October 1, 1993, and before July 1, 2006, we receive 98 percent reimbursement. For loans disbursed prior to October 1, 1993, we receive 100 percent reimbursement. The allowance for FFELP Loan losses uses historical experience of customer default behavior and a two -year loss emergence period to estimate the credit losses incurred in the loan portfolio at the reporting date. We apply the default rate projections, net of applicable risk sharing, to each category for the current period to perform our quantitative calculation. Once the quantitative calculation is performed, we review the adequacy of the allowance for loan losses and determine if qualitative adjustments need to be considered.
Deposits	Deposits Our retail deposit accounts are principally certificates of deposit (“CDs”), money market deposit accounts (“MMDAs”) and high-yield savings (“HYS”) accounts. CDs are accounts that have a stipulated maturity and interest rate. Retail CDs may be withdrawn early, but a penalty is assessed. MMDA and HYS accounts are both interest and non-interest bearing accounts that have no maturity or expiration date. For retail MMDA and HYS accounts, the depositor may be required to give written notice of any intended withdrawal not less than seven days before the withdrawal is made, although this provision is not generally enforced. The Bank also includes brokered CDs in its funding base. Early withdrawal of brokered CDs is prohibited (except in the case of death or legal incapacity). Other deposit accounts include large interest-bearing omnibus accounts deposited in the Bank by commercial entities having custodial responsibilities for many underlying accounts. These omnibus accounts may be structured with or without fixed maturities, and may have fixed or variable interest rates.
Upromise member accounts	Upromise member accounts Upromise member accounts represent amounts owed to Upromise rewards members for rebates they have earned from qualifying purchases from Upromise’s participating merchants. These amounts are held in trust for the benefit of the members until distributed in accordance with the Upromise member’s request and/or the terms of the Upromise service agreement. Upromise, which acts as the trustee for the trust, has deposited a majority of the cash with the Bank pursuant to a money market deposit account agreement between the Bank and Upromise as trustee of the trust.
Fair Value Measurement	Fair Value Measurement We use estimates of fair value in applying various accounting standards for our financial statements. Fair value measurements are used in one of four ways: • In the consolidated balance sheet with changes in fair value recorded in the consolidated statement of income; • In the consolidated balance sheet with changes in fair value recorded in the accumulated other comprehensive income section of the consolidated statement of changes in equity; • In the consolidated balance sheet for instruments carried at lower of cost or fair value with impairment charges recorded in the consolidated statement of income; and • In the notes to the consolidated financial statements. Fair value is defined as the price to sell an asset or transfer a liability in an orderly transaction between willing and able market participants. In general, our policy in estimating fair value is to first look at observable market prices for identical assets and liabilities in active markets, where available. When these are not available, other inputs are used to model fair value such as prices of similar instruments, yield curves, volatilities, prepayment speeds, default rates and credit spreads (including for our liabilities), relying first on observable data from active markets. Depending on current market conditions, additional adjustments to fair value may be based on factors such as liquidity, credit, and bid/offer spreads. Transaction costs are not included in the determination of fair value. When possible, we seek to validate the model’s output to market transactions. Depending on the availability of observable inputs and prices, different valuation models could produce materially different fair value estimates. The values presented may not represent future fair values and may not be realizable. 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. Classification is based on the lowest level of input that is significant to the fair value of the instrument. The three levels are as follows: • Level 1 — Quoted prices (unadjusted) in active markets for identical assets or liabilities that we have the ability to access at the measurement date. The types of financial instruments included in level 1 are highly liquid instruments with quoted prices. • Level 2 — Inputs from active markets, other than quoted prices for identical instruments, are used to determine fair value. Significant inputs are directly observable from active markets for substantially the full term of the asset or liability being valued. • Level 3 — Pricing inputs significant to the valuation are unobservable. Inputs are developed based on the best information available. However, significant judgment is required by us in developing the inputs.
Loan Interest Income	Loan Interest Income For all loans, including impaired loans, classified as “held for investment,” we recognize interest income as earned, adjusted for the amortization of deferred direct origination and acquisition costs. This adjustment is recognized based upon the expected yield of the loan over its life after giving effect to prepayments and extensions. We consider our constant prepayment rate (“CPR”) estimates a significant accounting assumption used to measure the expected prepayment activity in our education loan portfolio. The estimates are based on a number of factors such as historical prepayment rates for loans with similar loan characteristics, assumptions about portfolio composition and loan terms, and the prepayment curve’s tendency to follow a ramp pattern (i.e., the prepayment rate typically increases during the in-school and early repayment periods, then stabilizes). The CPR measures the expected prepayment activity over the life of the loan and is applied as a flat-rate input assumption when used in forecasting. Additionally, interest earned on education loans reflects potential non-payment adjustments in accordance with our uncollectible interest recognition policy as discussed further in “Allowance for Loan Losses” of this Note 2. Because of this, we do not place loans in nonaccrual status prior to charge-off. We do not amortize any adjustments to the basis of education loans when they are classified as held-for-sale. Our CPR estimates include the effect of voluntary prepayments and consolidation (if the loans are consolidated to third parties), both of which shorten the lives of loans. CPR estimates also consider the utilization of deferment, forbearance, and extended repayment plans, which lengthen the lives of loans. We regularly evaluate the assumptions used to estimate the CPRs. In instances where there are changes to the assumptions, amortization of deferred direct origination and acquisition costs is adjusted on a cumulative basis to reflect the change since the origination or purchase of the loan. For the year ended December 31, 2017, our CPR for Private Education Loans was 5.94 percent , compared with a CPR of 5.00 percent for the year ended December 31, 2016. We also pay to the U.S. Department of Education (the “DOE”) an annual 105 basis point Consolidation Loan Rebate Fee on FFELP consolidation loans, which is netted against loan interest income. Additionally, interest earned on education loans reflects potential non-payment adjustments in accordance with our uncollectible interest recognition policy. We do not amortize any adjustments to the basis of education loans when they are classified as “held-for-sale.” We recognize certain fee income (primarily late fees) on education loans when earned according to the contractual provisions of the promissory notes, as well as our expectation of collectability. Fee income is recorded when earned in “other non-interest income” in the accompanying consolidated statements of income.
Interest Expense	Interest Expense Interest expense is based upon contractual interest rates adjusted for the amortization of issuance costs. We incur interest expense on interest bearing deposits comprised of non-maturity savings deposits, brokered and retail CDs, and brokered and retail MMDAs, as well as on unsecured and secured financings. Interest expense is recognized when amounts are contractually due to deposit and debt holders and is adjusted for net payments/receipts related to interest rate swap agreements that qualify and are designated hedges of interest bearing liabilities. Interest expense also includes the amortization of deferred gains and losses on closed hedge transactions that qualified as hedges. Amortization of debt issuance costs, premiums, discounts and terminated hedge-basis adjustments are recognized using the effective interest rate method. We incur certain fees related to our Private Education Loan asset-backed commercial paper facility (the “ABCP Facility”), including an unused ABCP Facility fee, and also incur fees related to our term asset-backed securities (“ABS”). These fees are included in interest expense.
Gains on Sale of Loans, Net	Gains on Sale of Loans, Net We may participate and sell loans to third-parties and affiliates, including entities that were related parties prior to the Spin-Off. These sales may occur through whole loan sales or securitization transactions that qualify for sales treatment. If a transfer of loans qualifies as a sale, we derecognize the loan and recognize a gain or loss as the difference between the carry basis of the loan sold and liabilities retained and the compensation received. We recognize the results of a transfer of loans based upon the settlement date of the transaction. These loans were initially recorded as held for investment, and were transferred to held-for-sale immediately prior to sale or securitization.
Other Income	Other Income Our Upromise subsidiary has a number of programs that encourage consumers to save for the cost of college education. We have established a consumer savings network, which is designed to promote college savings by consumers who are members of this program by encouraging them to purchase goods and services from the merchants that participate in the program. Participating merchants generally pay Upromise fees based on member purchase volume, either online or in stores, depending on the contractual arrangement with the merchant. We recognize revenue as marketing and administrative services are rendered, based upon contractually determined rates and member purchase volumes. Also included in other income are late fees on both Private Education Loans and FFELP Loans, which we recognize when the cash has been received, fees related to our credit card affinity program, income for servicing private student loans for third-parties and changes to our tax indemnification receivable from Navient.
Securitization Accounting	Securitization Accounting Our securitizations transactions use a two-step structure with a special purpose entity VIE that legally isolates the transferred assets from us in the event of bankruptcy or receivership. Transactions receiving sale treatment are also structured to ensure that the holders of the beneficial interests issued are not constrained from pledging or exchanging their interests, and that we do not maintain effective control over the transferred assets. If these criteria are not met, then the transaction is accounted for as an on-balance sheet secured borrowing. If a securitization qualifies as a sale, we then assess whether we are the primary beneficiary of the securitization trust and are required to consolidate such trust. We are considered the primary beneficiary if we have 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. There can be considerable judgment as it relates to determining the primary beneficiary of the VIEs. There are no “bright line” tests. Rather, the assessment of who has the power to direct the activities of the VIE that most significantly affect the VIE’s economic performance and who has the obligation to absorb losses or receive benefits of the entity that could potentially be significant to the VIE can be very qualitative and judgmental in nature. If we are the primary beneficiary, then no gain or loss is recognized. We have determined that as the servicer of Sallie Mae securitization trusts, we meet the first primary beneficiary criterion because we have the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance. Irrespective of whether a securitization receives sale or on-balance sheet treatment, our continuing involvement with our securitization trusts is generally limited to: • Owning the equity certificates of certain trusts; • The servicing of the student loan assets within the securitization trusts, on both a pre- and post-default basis; • Our acting as administrator for the securitization transactions we sponsored; • Our responsibilities relative to representation and warranty violations; and • The option to exercise the clean-up call and purchase the student loans from the trust when the pool balance is 10 percent or less of the original pool balance. In 2015 and 2014, we executed both secured financing and securitized loan sale transactions. Based upon our relationships with these securitizations, we believe the consolidation assessment is straightforward. We consolidated our secured financing transactions because either we did not meet the accounting criterion for sales treatment or we determined we were the primary beneficiary of the VIE because we retained (a) the residual interest in the securitization and therefore had the obligation to absorb losses or receive benefits of the entity that could potentially be significant to the VIE as well as (b) the power to direct the activities of the VIE in our role as servicer. For those accounted for as securitized loan sales, we were not the primary beneficiary because we have no obligation to absorb losses or receive benefits of the entity that could potentially be significant to the VIE. The investors in our securitization trusts have no recourse to our other assets should there be a failure of the trust to pay when due. Generally, the only recourse the securitization trusts have to us is in the event we breach a seller representation or warranty or our duties as master servicer and servicer, in which event we are obligated to repurchase the related loans from the trust. We did not record a servicing asset or servicing liability related to our securitization transactions because we determined the servicing fees we receive are at market rate.
Derivative Accounting	Derivative Accounting We account for our derivatives, consisting of interest rate swaps, at fair value on the consolidated balance sheets as either an asset or liability. Derivative positions are recorded as net positions by counterparty based on master netting arrangements (see Note 11, “Derivative Financial Instruments”), exclusive of accrued interest and cash collateral held or pledged. The Chicago Mercantile Exchange (the “CME”) and the London Clearing House (the “LCH”) made amendments to their respective rules that resulted in the prospective accounting treatment of certain daily payments historically treated as the posting of collateral (variation margin payments) being considered as the legal settlement of the outstanding exposure of the derivative. While the CME rule, which became effective in January 2017, is mandatory, the LCH allows a clearing member institution the option to adopt the rule changes on an individual contract or portfolio basis. As of December 31, 2017, $4.8 billion notional of our derivative contracts were cleared on the CME and $0.7 billion were cleared on the LCH. The derivative contracts cleared through the CME and LCH represent 87.6 percent and 12.4 percent , respectively, of our total notional derivative contracts of $5.5 billion at December 31, 2017. Under this new rule, for derivatives cleared through the CME, 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 LCH clearing member institution has elected not to adopt the new rule change. Therefore, there has been no change to the accounting for the derivatives cleared through the LCH, and variation margin payments required to be exchanged based on the fair value of these derivatives remain accounted for as collateral. We determine the fair value for our derivative contracts primarily using pricing models that consider current market conditions and the contractual terms of the derivative contracts. These pricing models consider interest rates, time value, forward interest rate curves, and volatility factors. Inputs are generally from active financial markets. The majority of our derivatives qualify as effective hedges. For these derivatives, the relationship between the hedging instrument and the hedged items (including the hedged risk and method for assessing effectiveness), as well as the risk management objective and strategy for undertaking various hedge transactions at the inception of the hedging relationship, are documented. Each derivative is designated to a specific (or pool of) liability(ies) on the consolidated balance sheets, and is designated as either a “fair value” hedge or a “cash flow” hedge. Fair value hedges are designed to hedge our exposure to the changes in fair value of a fixed-rate liability. For effective fair value hedges, both the hedge and the hedged item (for the risk being hedged) are recorded at fair value with any difference reflecting ineffectiveness recorded immediately in the consolidated statements of income. Cash flow hedges are designed to hedge our exposure to variability in cash flows related to variable-rate deposits. The assessment of the hedge’s effectiveness is performed at inception and on an ongoing basis, using regression testing. For hedges of a pool of liabilities, tests are performed to demonstrate the similarity of individual instruments of the pool. When it is determined that a derivative is not currently an effective hedge, ineffectiveness is recognized for the full change in fair value of the derivative with no offsetting amount from the hedged item since the last time it was effective. If it is also determined the hedge will not be effective in the future, we discontinue the hedge accounting prospectively and begin amortization of any basis adjustments that exist related to the hedged item.
Stock-Based Compensation	Stock-Based Compensation We recognize stock-based compensation cost in our consolidated statements of income using the fair value method. Under this method, we determine the fair value of the stock-based compensation at the time of the grant and recognize the resulting compensation expense over the vesting period of the stock-based grant. We do not apply a forfeiture rate to our stock-based compensation expense, but rather record forfeitures when they occur. We record all excess tax benefits/deficiencies related to the settlement of employee stock-based compensation to the income tax expense line item on our consolidated statements of income.
Income Taxes	Income Taxes We account for income taxes under the asset and liability approach, which requires the recognition of deferred tax liabilities and assets for the expected future tax consequences of temporary differences between the carrying amounts and tax basis of our assets and liabilities. To the extent tax laws change, deferred tax assets and liabilities are adjusted in the period that the tax change is enacted. On December 22, 2017, President Trump signed into law the Tax Cuts and Jobs Act of 2017 (the “Tax Act”), which lowered federal corporate income tax rates from 35 percent to 21 percent, beginning January 1, 2018. Because the Tax Act was enacted during the fourth-quarter 2017, we were required to reflect the application of the lower tax rate in future years to our deferred assets, liabilities and indemnification receivables. We recognized additional discrete tax expense of $15 million for the year ended December 31, 2017, primarily due to the remeasurement of our deferred tax assets and liabilities following the enactment of the Tax Act. At December 31, 2017, our accounting for the Tax Act is complete under the SEC’s Staff Accounting Bulletin No. 118. Forthcoming guidance, such as regulations or technical corrections, could change how we interpreted provisions of the Tax Act. “Income tax expense (benefit)” includes (i) deferred tax expense (benefit), which represents the net change in the deferred tax asset or liability balance during the year when applicable, and (ii) current tax expense (benefit), which represents the amount of tax currently payable to or receivable from a tax authority plus amounts accrued for unrecognized tax benefits. Income tax expense (benefit) excludes the tax effects related to adjustments recorded in equity. An uncertain tax position is recognized only if it is more likely than not to be sustained upon examination based on the technical merits of the position. The amount of tax benefit recognized in the consolidated financial statements is the largest amount of benefit that is more than fifty percent likely of being sustained upon ultimate settlement of the uncertain tax position. We recognize interest and penalties related to unrecognized tax benefits in income tax expense (benefit).
Reclassifications	Reclassifications Certain reclassifications have been made to the balances as of and for the years ended December 31, 2016 and 2015, to be consistent with classifications adopted for 2017, which had no effect on net income, total assets or total liabilities.
Recently Issued but Not Yet Adopted Accounting Pronouncements	Recently Issued but Not Yet Adopted Accounting Pronouncements In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606).” The guidance in this ASU supersedes existing revenue recognition requirements in Topic 605, Revenue Recognition, including an assortment of transaction-specific and industry-specific rules. The new revenue recognition model is effective for the Company on January 1, 2018. This ASU establishes a principles-based model under which revenue from a contract is allocated to the distinct performance obligations within the contract and recognized in income as each performance obligation is satisfied. ASU Topic 606 does not apply to rights or obligations associated with financial instruments (for example, interest income from loans or investments, or interest expense on debt), and therefore our net interest income should not be affected. Certain of our fee income related to our Upromise rewards business is within the scope of these rules. Management has concluded that timing and measurement of fee income related to our Upromise rewards business will remain substantially unchanged under the new standard. This conclusion covers the vast majority of our revenue that is within the scope of the new standard. Upon adoption in 2018, management does not anticipate a restatement of prior period amounts. In March 2016, the FASB issued ASU No. 2016-08, “Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net).” The guidance in this ASU provides clarification on the principal versus agent concept in relation to revenue recognition guidance issued as part of ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606).” Topic 606 requires a company to determine whether it is a principal or an agent in a transaction in which another party is involved in providing goods or services to a customer by evaluating the nature of its promise to the customer. ASU No. 2016-08 provides clarification for identifying the good, service or right being transferred in a revenue transaction and identifies the principal as the party that controls the good, service or right prior to its transfer to the customer. The ASU provides further clarity on how to evaluate control in this context. The new standard is effective for the Company on January 1, 2018. We have concluded that this ASU will not result in different conclusions regarding our revenue arrangements that involve a principal-agent relationship. In January 2016, the FASB issued ASU No. 2016-01, “Financial Instruments-Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities.” The ASU does not change the guidance for classifying and measuring investments in debt securities or loans. The standard requires entities to measure certain cost-method equity investments at fair value with changes in value recognized in net income. Equity investments that do not have readily determinable fair values will be carried at cost, less any impairment, plus or minus changes resulting from any observable price changes in orderly transactions for an identical or similar investment of the same issuer. This ASU requires public entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes and requires separate presentation of financial assets and financial liabilities by measurement category and form of financial asset (i.e., securities or loans) on the balance sheet or the accompanying notes to the financial statements. We have concluded that the adoption in 2018 will not materially affect our consolidated financial statements. In February 2016, the FASB issued ASU No. 2016-02, “Leases,” a comprehensive new lease standard which will supersede previous lease guidance. The standard requires a lessee to recognize in its balance sheet assets and liabilities related to long-term leases that were classified as operating leases under previous guidance. An asset will be recognized related to the right to use the underlying asset and a liability will be recognized related to the obligation to make lease payments over the term of the lease. The standard also requires expanded disclosures surrounding leases. The standard is effective for fiscal periods beginning after December 15, 2018, and requires modified retrospective adoption, with early adoption permitted. The adoption of this guidance is not expected to have a material impact on our consolidated financial statements. In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.” This ASU eliminates the incurred loss threshold for initial recognition of credit impairment in current GAAP and replaces it with the expected loss concept. For all loans carried at amortized cost, we will be required to measure our allowance for loan losses based on our current estimate of all expected credit losses (“CECL”) over the remaining contractual term of the assets. Because it eliminates the incurred loss trigger, the new accounting guidance will require us, upon the origination of a loan, to record an estimate of all expected credit losses on that loan through an immediate charge to earnings. Updates to that estimate each period will be recorded through provision expense. The estimate of loan losses must be based on historical experience, current conditions and reasonable and supportable forecasts. The ASU does not mandate the use of any specific method for estimating credit loss, permitting companies to use judgment in selecting the approach that is most appropriate in their circumstances. The standard will become effective for us on January 1, 2020, with early adoption permitted no sooner than January 1, 2019. Upon adoption, a cumulative effect adjustment to retained earnings will be recorded as of the beginning of the first reporting period in which the guidance is effective in an amount necessary to adjust the allowance for loan losses to equal the current estimate of expected losses on financial assets held at that date. We have evaluated the standard and initiated implementation efforts. We recently identified our CECL systems solution provider and expect to finish implementing the system in 2018 and then run parallel to our current process in 2019, in preparation for the 2020 implementation date. Adoption of the standard will have a material impact on how we record and report our financial condition and results of operations, and on regulatory capital. The extent of the impact upon adoption will likely depend on the characteristics of our loan portfolio and economic conditions at that date, as well as forecasted conditions thereafter. In November 2016, the FASB issued 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. The ASU will become effective for us on January 1, 2018, and is not expected to have a material impact to our statement of cash flows. In May 2017, the FASB issued ASU 2017-09, “Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting, ” which clarifies what constitutes a modification of a share-based payment award. The ASU is effective for all entities for annual and interim periods in fiscal years beginning after December 15, 2017, with early adoption permitted. We have concluded that the adoption in 2018 will not materially affect our consolidated financial statements. On August 28, 2017, the FASB issued ASU 2017-12, “Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities,” which 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 make certain targeted improvements to simplify the application of the hedge accounting guidance. The guidance expands the ability to hedge nonfinancial and financial risk components, reduces complexity in fair value hedges of interest rate risk, eliminates the requirement to separately measure and report hedge ineffectiveness, as well as eases certain hedge effectiveness assessment requirements. The effective date for the standard is January 1, 2019, with early adoption permitted. We are currently evaluating if we will adopt this standard prior to its final effective date, and we currently do not expect the adoption to materially affect our consolidated financial statements.

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2017
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: 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 December 31, 2016 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Available for sale: Mortgage-backed securities $ 196,406 $ 929 $ (3,042 ) $ 194,293 Utah Housing Corporation bonds 15,000 — (690 ) 14,310 Total $ 211,406 $ 929 $ (3,732 ) $ 208,603
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 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 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 As of December 31, 2016: Mortgage-backed securities $ (2,423 ) $ 129,549 $ (619 ) $ 10,885 $ (3,042 ) $ 140,434 Utah Housing Corporation bonds (690 ) 14,310 — — (690 ) 14,310 Total $ (3,113 ) $ 143,859 $ (619 ) $ 10,885 $ (3,732 ) $ 154,744
Amortized cost and fair value of securities by contractual maturities	As of December 31, 2017 , 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 $ 272 $ 293 2039 3,406 3,606 2042 10,993 10,487 2043 37,438 37,534 2044 28,301 28,206 2045 41,082 40,484 2046 48,785 47,771 2047 77,330 75,707 Total $ 247,607 $ 244,088

Loans Held for Investment (Tabl

Loans Held for Investment (Tables)	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Loans held for investment	Loans held for investment are summarized as follows: December 31, 2017 2016 Private Education Loans $ 17,432,167 $ 14,251,675 Deferred origination costs 56,378 44,206 Allowance for loan losses (243,715 ) (182,472 ) Total Private Education Loans, net 17,244,830 14,113,409 FFELP Loans 927,660 1,010,908 Unamortized acquisition costs, net 2,631 2,941 Allowance for loan losses (1,132 ) (2,171 ) Total FFELP Loans, net 929,159 1,011,678 Personal Loans 400,280 12,893 Allowance for loan losses (6,628 ) (58 ) Total Personal Loans, net 393,652 12,835 Loans held for investment, net $ 18,567,641 $ 15,137,922 The estimated weighted average life of education loans in our portfolio was approximately 5.5 years and 6.0 years at December 31, 2017 and 2016 , respectively. The average balance and the respective weighted average interest rates of loans in our portfolio are summarized as follows: Years Ended December 31, 2017 2016 2015 Average Balance Weighted Average Interest Rate Average Balance Weighted Average Interest Rate Average Balance Weighted Average Interest Rate Private Education Loans $ 16,176,351 8.43 % $ 12,747,756 8.02 % $ 9,819,053 7.93 % FFELP Loans 970,738 3.91 1,063,325 3.53 1,179,723 3.26 Personal Loans 112,644 9.90 710 8.53 — — Total portfolio $ 17,259,733 $ 13,811,791 $ 10,998,776
Loans held for investment by Region	At December 31, 2017 , 40.4 percent of total education loans were concentrated in the following states: 2017 New York 10.5 % California 9.3 Pennsylvania 8.5 New Jersey 6.9 Illinois 5.2 40.4 % At December 31, 2016 , 40.3 percent of total education loans were concentrated in the following states: 2016 New York 10.3 % California 9.4 Pennsylvania 8.4 New Jersey 6.9 Illinois 5.3 40.3 %

Allowance for Loan Losses (Tabl

Allowance for Loan Losses (Tables)	12 Months Ended
	Dec. 31, 2017
Receivables [Abstract]
Allowance for credit losses and recorded investments in loans	Allowance for Loan Losses Metrics Allowance for Loan Losses Year Ended December 31, 2017 FFELP Loans Private Education Loans Personal Loans Total Allowance for Loan Losses Beginning balance $ 2,171 $ 182,472 $ 58 $ 184,701 Total provision (85 ) 178,542 7,138 185,595 Net charge-offs: Charge-offs (954 ) (130,063 ) (579 ) (131,596 ) Recoveries — 17,635 11 17,646 Net charge-offs (954 ) (112,428 ) (568 ) (113,950 ) Loan sales (1) — (4,871 ) — (4,871 ) Ending Balance $ 1,132 $ 243,715 $ 6,628 $ 251,475 Allowance: Ending balance: individually evaluated for impairment $ — $ 94,682 $ — $ 94,682 Ending balance: collectively evaluated for impairment $ 1,132 $ 149,033 $ 6,628 $ 156,793 Loans: Ending balance: individually evaluated for impairment $ — $ 990,351 $ — $ 990,351 Ending balance: collectively evaluated for impairment $ 927,660 $ 16,441,816 $ 400,280 $ 17,769,756 Net charge-offs as a percentage of average loans in repayment (2) 0.13 % 1.03 % 0.47 % Allowance as a percentage of the ending total loan balance 0.12 % 1.40 % 1.66 % Allowance as a percentage of the ending loans in repayment (2) 0.15 % 2.00 % 1.66 % Allowance coverage of net charge-offs 1.19 2.17 11.67 Ending total loans, gross $ 927,660 $ 17,432,167 $ 400,280 Average loans in repayment (2) $ 745,039 $ 10,881,058 $ 119,606 Ending loans in repayment (2) $ 746,456 $ 12,206,033 $ 400,280 ____________ (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 Year Ended December 31, 2016 FFELP Loans Private Education Loans Personal Loans Total Allowance for Loan Losses Beginning balance $ 3,691 $ 108,816 $ — $ 112,507 Total provision (172 ) 159,511 58 159,397 Net charge-offs: Charge-offs (1,348 ) (90,203 ) — (91,551 ) Recoveries — 10,382 — 10,382 Net charge-offs (1,348 ) (79,821 ) — (81,169 ) Loan sales (1) — (6,034 ) — (6,034 ) Ending Balance $ 2,171 $ 182,472 $ 58 $ 184,701 Allowance: Ending balance: individually evaluated for impairment $ — $ 86,930 $ — $ 86,930 Ending balance: collectively evaluated for impairment $ 2,171 $ 95,542 $ 58 $ 97,771 Loans: Ending balance: individually evaluated for impairment $ — $ 612,606 $ — $ 612,606 Ending balance: collectively evaluated for impairment $ 1,010,908 $ 13,639,069 $ 12,894 $ 14,662,871 Net charge-offs as a percentage of average loans in repayment (2) 0.17 % 0.96 % — % Allowance as a percentage of the ending total loan balance 0.21 % 1.28 % — % Allowance as a percentage of the ending loans in repayment (2) 0.28 % 1.88 % — % Allowance coverage of net charge-offs 1.61 2.29 — Ending total loans, gross $ 1,010,908 $ 14,251,675 $ — Average loans in repayment (2) $ 793,203 $ 8,283,036 $ — Ending loans in repayment (2) $ 786,332 $ 9,709,758 $ — ____________ (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 Year Ended December 31, 2015 FFELP Loans Private Education Loans Total Allowance for Loan Losses Beginning balance $ 5,268 $ 78,574 $ 83,842 Total provision 1,005 87,344 88,349 Net charge-offs: Charge-offs (2,582 ) (55,357 ) (57,939 ) Recoveries — 5,820 5,820 Net charge-offs (2,582 ) (49,537 ) (52,119 ) Loan sales (1) — (7,565 ) (7,565 ) Ending Balance $ 3,691 $ 108,816 $ 112,507 Allowance: Ending balance: individually evaluated for impairment $ — $ 43,480 $ 43,480 Ending balance: collectively evaluated for impairment $ 3,691 $ 65,336 $ 69,027 Loans: Ending balance: individually evaluated for impairment $ — $ 265,831 $ 265,831 Ending balance: collectively evaluated for impairment $ 1,115,663 $ 10,330,606 $ 11,446,269 Net charge-offs as a percentage of average loans in repayment (2) 0.30 % 0.82 % Allowance as a percentage of the ending total loan balance 0.33 % 1.03 % Allowance as a percentage of the ending loans in repayment (2) 0.45 % 1.57 % Allowance coverage of net charge-offs 1.43 2.20 Ending total loans, gross $ 1,115,663 $ 10,596,437 Average loans in repayment (2) $ 857,359 $ 6,031,741 Ending loans in repayment (2) $ 813,815 $ 6,927,266 ____________ (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.
Unpaid principal balance and related allowance for TDR loans	At December 31, 2017 and 2016 , all of our 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 December 31, 2017 TDR Loans $ 1,007,141 $ 990,351 $ 94,682 December 31, 2016 TDR Loans $ 620,991 $ 612,606 $ 86,930
Average recorded investment and interest income recognized	The following table provides the average recorded investment and interest income recognized for our TDR loans. Years Ended December 31, 2017 2016 2015 Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized TDR Loans $ 822,145 $ 61,119 $ 422,527 $ 30,700 $ 174,087 $ 14,081
Age analysis of past due loans delinquencies	The following table provides information regarding the loan status and aging of TDR loans. December 31, December 31, 2017 2016 Balance % Balance % TDR loans in in-school/grace/deferment (1) $ 51,745 $ 24,185 TDR loans in forbearance (2) 69,652 71,851 TDR loans in repayment (3) and percentage of each status: Loans current 774,222 89.1 % 462,187 89.5 % Loans delinquent 31-60 days (4) 48,377 5.6 28,452 5.5 Loans delinquent 61-90 days (4) 28,778 3.3 17,326 3.4 Loans delinquent greater than 90 days (4) 17,577 2.0 8,605 1.6 Total TDR loans in repayment 868,954 100.0 % 516,570 100.0 % Total TDR loans, gross $ 990,351 $ 612,606 _____ (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. ___________ (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 Private Education Loans. 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. Private Education Loans December 31, 2017 2016 2015 Balance % Balance % Balance % Loans in-school/grace/deferment (1) $ 4,757,732 $ 4,189,955 $ 3,427,964 Loans in forbearance (2) 468,402 351,962 241,207 Loans in repayment and percentage of each status: Loans current 11,911,128 97.6 % 9,509,394 97.9 % 6,773,095 97.8 % Loans delinquent 31-60 days (3) 179,002 1.5 124,773 1.3 91,129 1.3 Loans delinquent 61-90 days (3) 78,292 0.6 51,423 0.5 42,048 0.6 Loans delinquent greater than 90 days (3) 37,611 0.3 24,168 0.3 20,994 0.3 Total Private Education Loans in repayment 12,206,033 100.0 % 9,709,758 100.0 % 6,927,266 100.0 % Total Private Education Loans, gross 17,432,167 14,251,675 10,596,437 Private Education Loans deferred origination costs 56,378 44,206 27,884 Total Private Education Loans 17,488,545 14,295,881 10,624,321 Private Education Loans allowance for losses (243,715 ) (182,472 ) (108,816 ) Private Education Loans, net $ 17,244,830 $ 14,113,409 $ 10,515,505 Percentage of Private Education Loans in repayment 70.0 % 68.1 % 65.4 % Delinquencies as a percentage of Private Education Loans in repayment 2.4 % 2.1 % 2.2 % Loans in forbearance as a percentage of Private Education Loans in repayment and forbearance 3.7 % 3.5 % 3.4 % (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.
Modified loans accounts for troubled debt restructuring	The following table provides the amount of modified loans (which includes 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 60 days past due for this disclosure. Years Ended December 31, 2017 2016 2015 Modified Loans (1) Charge-offs Payment-Default Modified Loans (1) Charge-offs Payment-Default Modified Loans (1) Charge-offs Payment-Default TDR Loans $ 498,812 $ 48,469 $ 92,532 $ 398,324 $ 24,628 $ 64,811 $ 244,890 $ 10,877 $ 51,602 _______ (1) Represents the principal balance of loans that have been modified during the period and resulted in a TDR.
Private education loan portfolio stratified by key credit quality indicators	The following table highlights the gross principal balance of our Personal Loan portfolio stratified by key credit quality indicators. Personal Loans Credit Quality Indicators December 31, 2017 December 31, 2016 Credit Quality Indicators: Balance (1) % of Balance Balance (1) % of Balance FICO at Original Approval: Less than 670 $ 32,156 8 % $ 1,189 9 % 670-699 114,731 29 3,139 24 700-749 182,025 45 5,678 44 Greater than or equal to 750 71,368 18 2,888 23 Total $ 400,280 100 % $ 12,894 100 % Seasoning (2) : 0-12 payments $ 400,280 100 % $ 12,894 100 % 13-24 payments — — — — 25-36 payments — — — — 37-48 payments — — — — More than 48 payments — — — — Total $ 400,280 100 % $ 12,894 100 % ___________ (1) Balance represents gross Personal Loans. (2) Number of months in active repayment for which a scheduled payment was due. The following table highlights the gross principal balance of our Private Education Loan portfolio stratified by key credit quality indicators. December 31, 2017 December 31, 2016 Credit Quality Indicators: Balance (1) % of Balance Balance (1) % of Balance Cosigners: With cosigner $ 15,658,539 90 % $ 12,816,512 90 % Without cosigner 1,773,628 10 1,435,163 10 Total $ 17,432,167 100 % $ 14,251,675 100 % FICO at Original Approval (2) : Less than 670 $ 1,153,591 6 % $ 920,132 6 % 670-699 2,596,959 15 2,092,722 15 700-749 5,714,554 33 4,639,958 33 Greater than or equal to 750 7,967,063 46 6,598,863 46 Total $ 17,432,167 100 % $ 14,251,675 100 % Seasoning (3) : 1-12 payments $ 4,256,592 24 % $ 3,737,110 26 % 13-24 payments 3,229,465 19 2,841,107 20 25-36 payments 2,429,238 14 1,839,764 13 37-48 payments 1,502,327 9 917,633 7 More than 48 payments 1,256,813 7 726,106 5 Not yet in repayment 4,757,732 27 4,189,955 29 Total $ 17,432,167 100 % $ 14,251,675 100 % ___________ (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.
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 portfolio for all periods presented. Private Education Loan Accrued Interest Receivable Total Interest Receivable Greater Than 90 Days Past Due Allowance for Uncollectible Interest December 31, 2017 $ 951,138 $ 1,372 $ 4,664 December 31, 2016 $ 739,847 $ 845 $ 2,898

Premises and Equipment, Net (Ta

Premises and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	The following is a summary of our premises and equipment. December 31, 2017 2016 Land and land improvements $ 12,356 $ 12,574 Buildings and leasehold improvements 61,409 60,919 Furniture, fixtures and equipment 15,261 15,026 Software 55,205 47,688 Premises and equipment, gross 144,231 136,207 Accumulated depreciation (54,483 ) (49,144 ) Premises and equipment, net $ 89,748 $ 87,063

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2017
Deposits [Abstract]
Schedule of deposits	The following table summarizes total deposits at December 31, 2017 and 2016 . December 31, 2017 2016 Deposits - interest bearing $ 15,504,330 $ 13,434,990 Deposits - non-interest bearing 1,053 677 Total deposits $ 15,505,383 $ 13,435,667
Interest bearing deposits	Interest bearing deposits at December 31, 2017 and 2016 are summarized as follows: December 31, 2017 December 31, 2016 Amount Year-End Weighted Average Stated Rate (1) Amount Year-End Weighted Average Stated Rate (1) Money market $ 7,731,966 1.80 % $ 7,129,404 1.22 % Savings 738,243 1.10 % 834,521 0.84 % Certificates of deposit 7,034,121 1.93 % 5,471,065 1.41 % Deposits - interest bearing $ 15,504,330 $ 13,434,990 ___ (1) Includes the effect of interest rate swaps in effective hedge relationships.
Schedule of maturities of time deposits	Certificates of deposit remaining maturities are summarized as follows: December 31, 2017 2016 One year or less $ 3,716,183 $ 2,565,246 After one year to two years 1,550,130 1,364,812 After two years to three years 806,488 936,125 After three years to four years 447,592 225,245 After four years to five years 445,884 379,637 After five years 67,844 — Total $ 7,034,121 $ 5,471,065

Borrowings (Tables)

Borrowings (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Secured borrowings	The following table summarizes our secured borrowings at December 31, 2017 and 2016. December 31, 2017 December 31, 2016 Short-Term Long-Term Total Short-Term Long-Term Total Unsecured borrowings: Unsecured debt $ — $ 196,539 $ 196,539 $ — $ — $ — Total unsecured borrowings — 196,539 196,539 — — — Secured borrowings: Private Education Loan term securitizations — 3,078,731 3,078,731 — 2,167,979 2,167,979 ABCP Facility — — — — — — Total secured borrowings — 3,078,731 3,078,731 — 2,167,979 2,167,979 Total $ — $ 3,275,270 $ 3,275,270 $ — $ 2,167,979 $ 2,167,979
Short-term borrowings	The following table summarizes the outstanding short-term borrowings, the weighted average interest rates at the end of the period and the related average balance and weighted average interest rates during the period. The ABCP Facility’s contractual maturity is two years from the date of inception or renewal ( one -year revolving period plus a one -year amortization period); however, we classify advances under our ABCP Facility as short-term borrowings because it is our intention to repay those advances within one year. Rates reflect stated interest of borrowings and related discounts and premiums. December 31, 2017 Year Ended December 31, 2017 Ending Balance Weighted Average Interest Rate Average Balance Weighted Average Interest Rate Short-term borrowings: ABCP Facility $ — — % $ 81,370 6.09 % Maximum outstanding at any month end $ 300,000 December 31, 2016 Year Ended December 31, 2016 Ending Balance Weighted Average Interest Rate Average Balance Weighted Average Interest Rate Short-term borrowings: ABCP Facility $ — — % $ 229,719 2.61 % Maximum outstanding at any month end $ 526,500
Long-term borrowings	The following table summarizes the outstanding long-term borrowings, the weighted average interest rates at the end of the period and the related average balance during the period. Rates reflect stated interest of borrowings and related discounts and premiums. The long-term borrowings amortize over time and mature serially from 2023 to 2040. December 31, 2017 Year Ended December 31, 2016 Year Ended December 31, 2016 Ending Balance Weighted Average Average Balance Ending Balance Weighted Average Interest Rate Average Balance Floating rate borrowings $ 1,512,970 2.32 % $ 1,422,856 $ 1,175,819 1.71 % $ 687,580 Fixed rate borrowings 1,762,300 3.04 1,420,737 992,160 2.68 548,465 Total long-term borrowings $ 3,275,270 2.71 % $ 2,843,593 $ 2,167,979 2.15 % $ 1,236,045
Secured financing	Secured Financings 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 loans 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 I month LIBOR plus 0.80% 4.07 — Total notes issued in 2017 $ 1,448,000 Total loans and accrued interest amount securitized at inception in 2017 $ 1,606,804 ____________ (1) Represents LIBOR equivalent cost of funds for floating and fixed rate bonds, excluding issuance costs.
Schedule of variable interest entities	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 December 31, 2016 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 $ — $ 2,167,979 $ 2,167,979 $ 2,562,156 $ 44,617 $ 160,783 $ 2,767,556 ABCP Facility — — — — — — — Total $ — $ 2,167,979 $ 2,167,979 $ 2,562,156 $ 44,617 $ 160,783 $ 2,767,556 ________ (1) Other assets primarily represent accrued interest receivable.

Derivative Financial Instrume40

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
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 December 31, 2017 and 2016 , and their impact on earnings and other comprehensive income for the years ended December 31, 2017 , 2016 and 2015 . The net fair value of derivative instruments as of December 31, 2017 was a liability of $1.8 million , compared to the net fair value as of December 31, 2016 liability of $18.1 million . The change in the net fair value reflects a $3.5 million decrease in fair value offset by variation margin amounts of $19.9 million . The net position as of December 31, 2017 was a $19.8 million liability, compared to a $30.0 million liability as of December 31, 2016. The change in the net position reflects a $3.5 million decrease in fair value, $32.1 million decrease in collateral held and pledged (for contracts other than those cleared through the CME), offset by variation margin impacts of $25.4 million . Impact of Derivatives on the Consolidated Balance Sheets Cash Flow Hedges Fair Value Hedges Trading Total December 31, December 31, December 31, December 31, December 31, December 31, December 31, December 31, 2017 2016 2017 2016 2017 2016 2017 2016 Fair Values (1) Hedged Risk Exposure Derivative Assets: (2) Interest rate swaps Interest rate $ — $ — $ 630 $ 7,808 $ 182 $ — $ 812 $ 7,808 Derivative Liabilities: (2) Interest rate swaps Interest rate (2,584 ) (14,463 ) — (10,398 ) — (1,076 ) (2,584 ) (25,937 ) Total net derivatives $ (2,584 ) $ (14,463 ) $ 630 $ (2,590 ) $ 182 $ (1,076 ) $ (1,772 ) $ (18,129 ) (1) Except for instruments cleared through the CME, fair values reported are exclusive of collateral held and pledged 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. The net position includes the variation margin as legal settlement of the derivative contract for instruments cleared through the CME. (2) The following table reconciles gross positions with the impact of master netting agreements to the balance sheet classification: Other Assets Other Liabilities December 31, December 31, December 31, December 31, 2017 2016 2017 2016 Gross position (1) $ 812 $ 7,808 $ (2,584 ) $ (25,937 ) Impact of master netting agreement (812 ) (7,808 ) 812 7,808 Derivative values with impact of master netting agreements (as carried on balance sheet) — — (1,772 ) (18,129 ) Cash collateral (held) pledged (2) — — 21,586 48,134 Net position $ — $ — $ 19,814 $ 30,005 (1) Except for instruments cleared with the CME, gross position amounts are exclusive of accrued interest and collateral held and pledged. (2) Cash collateral (held) 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 December 31, December 31, December 31, December 31, 2017 2016 2017 2016 Gross position (1) $ 812 $ 7,808 $ (2,584 ) $ (25,937 ) Impact of master netting agreement (812 ) (7,808 ) 812 7,808 Derivative values with impact of master netting agreements (as carried on balance sheet) — — (1,772 ) (18,129 ) Cash collateral (held) pledged (2) — — 21,586 48,134 Net position $ — $ — $ 19,814 $ 30,005 (1) Except for instruments cleared with the CME, gross position amounts are exclusive of accrued interest and collateral held and pledged. (2) Cash collateral (held) pledged excludes amounts that represent legal settlement of the derivative contracts.
Offsetting liabilities	The following table reconciles gross positions with the impact of master netting agreements to the balance sheet classification: Other Assets Other Liabilities December 31, December 31, December 31, December 31, 2017 2016 2017 2016 Gross position (1) $ 812 $ 7,808 $ (2,584 ) $ (25,937 ) Impact of master netting agreement (812 ) (7,808 ) 812 7,808 Derivative values with impact of master netting agreements (as carried on balance sheet) — — (1,772 ) (18,129 ) Cash collateral (held) pledged (2) — — 21,586 48,134 Net position $ — $ — $ 19,814 $ 30,005 (1) Except for instruments cleared with the CME, gross position amounts are exclusive of accrued interest and collateral held and pledged. (2) Cash collateral (held) 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 December 31, December 31, December 31, December 31, December 31, December 31, December 31, December 31, 2017 2016 2017 2016 2017 2016 2017 2016 Notional Values Interest rate swaps $ 1,408,649 $ 1,054,688 $ 3,062,849 $ 3,628,062 $ 987,577 $ 494,638 $ 5,459,075 $ 5,177,388
Schedule of derivative instruments performance and location	Impact of Derivatives on the Consolidated Statements of Income Years Ended December 31, 2017 2016 2015 Fair Value Hedges Interest rate swaps: Hedge ineffectiveness realized gains (losses) recorded in earnings (1) $ (4,557 ) $ (1,035 ) $ 2,695 Realized gains recorded in interest expense 8,286 27,810 29,940 Total $ 3,729 $ 26,775 $ 32,635 Cash Flow Hedges Interest rate swaps: Hedge ineffectiveness gains (losses) recorded in earnings (1) $ 53 $ (1,579 ) $ (1,427 ) Realized losses recorded in interest expense (11,187 ) (17,665 ) (21,475 ) Total $ (11,134 ) $ (19,244 ) $ (22,902 ) Trading Interest rate swaps: Interest reclassification $ (69 ) $ 2,170 $ 3,451 Realized gains (losses) recorded in earnings (3,693 ) (513 ) 581 Total (1) (3,762 ) 1,657 4,032 Total $ (11,167 ) $ 9,188 $ 13,765 _______ (1) Amounts included in “gains (losses) on derivatives and hedging activities, net” in the consolidated statements of income.
Schedule of derivative instruments, effect on other comprehensive income (loss)	Impact of Derivatives on the Statements of Changes in Stockholders’ Equity Years Ended December 31, 2017 2016 2015 Amount of gain (loss) recognized in other comprehensive income (loss) $ 8,008 $ (3,901 ) $ (26,699 ) Amount of loss reclassified in interest expense (1) (11,187 ) (17,665 ) (21,475 ) Total change in other comprehensive income (loss) for unrealized gains (losses) on derivatives, before income tax (expense) benefit $ 19,195 $ 13,764 $ (5,224 ) ______ (1) Amounts included in “realized losses recorded in interest expense” in the “Impact of Derivatives on the Consolidated Statements of Income” table.

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Class of Treasury Stock	The following table summarizes our common share repurchases and issuances associated with these programs. Years Ended December 31, (Shares and per share amounts in actuals) 2017 2016 2015 Shares repurchased related to employee stock-based compensation plans (1) 3,358,417 3,354,730 3,008,913 Average purchase price per share $11.96 $7.83 $9.65 Common shares issued (2) 6,831,108 5,955,045 5,873,309 _________ (1) Comprises 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) Common shares issued under our various compensation and benefit plans.

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2017
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. Years Ended December 31, (In thousands, except per share data) 2017 2016 2015 Numerator: Net income $ 288,934 $ 250,327 $ 274,284 Preferred stock dividends 15,714 21,204 19,595 Net income attributable to SLM Corporation common stock $ 273,220 $ 229,123 $ 254,689 Denominator: Weighted average shares used to compute basic EPS 431,216 427,876 425,574 Effect of dilutive securities: Dilutive effect of stock options, restricted stock, restricted stock units and Employee Stock Purchase Plan (“ESPP”) (1)(2) 7,335 5,043 6,660 Weighted average shares used to compute diluted EPS 438,551 432,919 432,234 Basic earnings per common share attributable to SLM Corporation $ 0.63 $ 0.54 $ 0.60 Diluted earnings per common share attributable to SLM Corporation $ 0.62 $ 0.53 $ 0.59 __________ (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 years ended December 31, 2017 , 2016 and 2015 , securities covering approximately 0 , 1 million and 2 million shares, respectively, were outstanding but not included in the computation of diluted earnings per share because they were anti-dilutive.

Stock-Based Compensation Plan43

Stock-Based Compensation Plans and Arrangements (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock option activity	The following table summarizes stock option activity for the year ended December 31, 2017 . (Dollars in thousands, except per share data) Number of Options Weighted Average Exercise Price per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (1) Outstanding at December 31, 2016 7,595,059 $ 10.43 Granted — — Exercised (2)(3) (2,693,347 ) 5.80 Canceled (440,719 ) 15.82 Outstanding at December 31, 2017 (4) 4,460,993 $ 11.34 1.2 years $ 26,413 Exercisable at December 31, 2017 4,460,993 $ 5.38 1.2 years $ 26,413 ____________ (1) The aggregate intrinsic value represents the total intrinsic value (the aggregate difference between our closing stock price on December 31, 2017 and the exercise price of in-the-money options) that would have been received by the option holders if all in-the-money options had been exercised on December 31, 2017. (2) The total intrinsic value of options exercised was $16.5 million, $9.3 million, and $13.7 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. (3) Cash of $0.1 million was received from option exercises for the year ended December 31, 2017. The actual tax benefit realized for the tax deductions from option exercises totaled $2.7 million for the year ended December 31, 2017. (4) For net-settled options, gross number is reflected.
Restricted stock activity	The following table summarizes restricted stock activity for the year ended December 31, 2017 . (Shares and per share amounts in actuals) Number of Shares Weighted Average Grant Date Fair Value Non-vested at December 31, 2016 120,879 $ 6.37 Granted 81,103 10.85 Vested (1) (120,879 ) 6.37 Canceled — — Non-vested at December 31, 2017 (2) 81,103 $ 10.85 _________ (1) The total fair value of shares that vested during the years ended December 31, 2017 , 2016 and 2015 was $0.8 million, $0.8 million and $0.5 million, respectively. (2) As of December 31, 2017 , there was $0.4 million of unrecognized compensation cost related to restricted stock, which is expected to be recognized over a weighted average period of 0.5 years .
Restricted stock unit and performance stock unit activity	The following table summarizes RSU and PSU activity for the year ended December 31, 2017 . (Shares and per share amounts in actuals) Number of RSUs/ PSUs Weighted Average Grant Date Fair Value Outstanding at December 31, 2016 7,486,610 $ 7.21 Granted 2,247,337 11.79 Vested and converted to common stock (1) (3,765,803 ) 7.75 Canceled (22,854 ) 8.82 Outstanding at December 31, 2017 (2) 5,945,290 $ 8.60 __________ (1) The total fair value of RSUs/PSUs that vested and converted to common stock during the years ended December 31, 2017 , 2016 and 2015 was $29.2 million, $22.2 million and $18.9 million, respectively. (2) As of December 31, 2017 , there was $13.4 million of unrecognized compensation cost related to RSUs/PSUs, which is expected to be recognized over a weighted average period of 1.4 years .
Black-Scholes Model assumptions for calculating ESPP fair values	The fair values of the stock purchase rights of the ESPP offerings were calculated using a Black-Scholes option pricing model with the following weighted average assumptions: Years Ended December 31, (Dollars per share) 2017 2016 2015 Risk-free interest rate 1.22 % 0.50 % 0.33 % Expected volatility 32 % 32 % 27 % Expected dividend rate — % — % — % Expected life of the option 1 year 1 year 1 year Weighted average fair value of stock purchase rights $ 2.36 $ 1.53 $ 1.74

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
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 December 31, 2017 December 31, 2016 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Available-for-sale investments $ — $ 244,088 $ — $ 244,088 $ — $ 208,603 $ — $ 208,603 Derivative instruments — 812 — 812 — 7,808 — 7,808 Total $ — $ 244,900 $ — $ 244,900 $ — $ 216,411 $ — $ 216,411 Liabilities Derivative instruments $ — $ (2,584 ) $ — $ (2,584 ) $ — $ (25,937 ) $ — $ (25,937 ) Total $ — $ (2,584 ) $ — $ (2,584 ) $ — $ (25,937 ) $ — $ (25,937 )
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. December 31, 2017 December 31, 2016 Fair Value Carrying Value Difference Fair Value Carrying Value Difference Earning assets Loans held for investment, net $ 20,673,136 $ 18,567,641 $ 2,105,495 $ 16,520,786 $ 15,137,922 $ 1,382,864 Cash and cash equivalents 1,534,339 1,534,339 — 1,918,793 1,918,793 — Available-for-sale investments 244,088 244,088 — 208,603 208,603 — Accrued interest receivable 967,482 967,482 — 766,106 766,106 — Tax indemnification receivable 168,011 168,011 — 259,532 259,532 — Derivative instruments 812 812 — 7,808 7,808 — Total earning assets $ 23,587,868 $ 21,482,373 $ 2,105,495 $ 19,681,628 $ 18,298,764 $ 1,382,864 Interest-bearing liabilities Money-market and savings accounts $ 8,470,209 $ 8,470,209 $ — $ 7,963,925 $ 7,963,925 $ — Certificates of deposit 7,044,208 7,034,121 (10,087 ) 5,510,504 5,471,065 (39,439 ) Short-term borrowings — — — — — — Long-term borrowings 3,299,871 3,275,270 (24,601 ) 2,160,105 2,167,979 7,874 Accrued interest payable 35,363 35,363 — 21,058 21,058 — Derivative instruments 2,584 2,584 — 25,937 25,937 — Total interest-bearing liabilities $ 18,852,235 $ 18,817,547 $ (34,688 ) $ 15,681,529 $ 15,649,964 $ (31,565 ) Excess of net asset fair value over carrying value $ 2,070,807 $ 1,351,299

Regulatory Capital (Tables)

Regulatory Capital (Tables)	12 Months Ended
	Dec. 31, 2017
Banking and Thrift [Abstract]
Schedule of compliance with regulatory capital requirements	The following capital amounts and ratios are based upon the Bank’s assets. Actual “Well Capitalized” Amount Ratio Amount Ratio 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 % As of December 31, 2016: Common Equity Tier 1 Capital (to Risk-Weighted Assets) $ 2,011,583 12.6 % $ 1,038,638 > 6.5 % Tier 1 Capital (to Risk-Weighted Assets) $ 2,011,583 12.6 % $ 1,278,323 > 8.0 % Total Capital (to Risk-Weighted Assets) $ 2,197,997 13.8 % $ 1,597,904 > 10.0 % Tier 1 Capital (to Average Assets) $ 2,011,583 11.1 % $ 907,565 > 5.0 %

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Reconciliations of statutory U.S. federal income tax rates to our effective tax rate	Reconciliations of the statutory U.S. federal income tax rates to our effective tax rate for continuing operations follow: Years Ended December 31, 2017 2016 2015 Statutory rate 35.0 % 35.0 % 35.0 % Tax reform 3.1 — — State tax, net of federal benefit 2.6 3.1 3.0 Reverse federal impact of indemnification adjustments 2.5 (0.7 ) 0.1 Unrecognized tax benefits, U.S. federal and state, net of federal benefit (2.0 ) 1.6 (0.5 ) Excess tax benefits/deficiencies for employee stock-based compensation, federal and state, net of federal benefit (1.7 ) — — Impact of state rate change on net deferred tax liabilities, net of federal benefit 0.6 (0.5 ) 0.5 State, valuation allowance adjustments on net operating losses 0.2 1.0 (0.2 ) Other, net 0.9 0.1 (0.4 ) Effective tax rate 41.2 % 39.6 % 37.5 %
Components of provision for income tax expense (benefit)	Income tax expense consists of: December 31, 2017 2016 2015 Current provision: Federal $ 248,191 $ 228,505 $ 215,950 State 13,092 24,336 26,057 Total current provision 261,283 252,841 242,007 Deferred (benefit)/provision: Federal (58,124 ) (89,518 ) (69,546 ) State (628 ) 786 (7,681 ) Total deferred benefit (58,752 ) (88,732 ) (77,227 ) Provision for income tax expense $ 202,531 $ 164,109 $ 164,780
Schedule of deferred tax assets and liabilities	The tax effect of temporary differences that give rise to deferred tax assets and liabilities is summarized below. The December 31, 2016 amounts were based upon a 35 percent statutory U.S. federal income tax rate, and the December 31, 2017 amounts were based upon a 21 percent statutory U.S. federal income tax rate. December 31, 2017 2016 Deferred tax assets: Loan reserves $ 62,603 $ 72,125 Stock-based compensation plans 10,216 16,471 Deferred revenue 782 793 Operating loss carryovers 4,186 8,371 Unrealized losses — 5,364 Accrued expenses not currently deductible 5,356 13,605 Unrecorded tax benefits 3,781 5,702 Other 2,410 10,844 Total deferred tax assets 89,334 133,275 Deferred tax liabilities: Gains on repurchased debt 40,175 126,403 Fixed assets 5,303 6,831 Acquired intangible assets 4,595 6,288 Unrealized gains 1,104 — Federal deferred for state receivable 3,584 2,058 Other 1,349 875 Total deferred tax liabilities 56,110 142,455 Net deferred tax liabilities $ 33,224 $ (9,180 )
Summary of changes in unrecognized tax benefits	The following table summarizes changes in unrecognized tax benefits: December 31, 2017 2016 2015 Unrecognized tax benefits at beginning of year $ 152,581 $ 47,109 $ 59,405 Increases resulting from tax positions taken during a prior period 7,482 110,894 3,456 Decreases resulting from tax positions taken during a prior period (7,025 ) (3,285 ) (10,121 ) Increases resulting from tax positions taken during the current period 1,656 817 3,447 Decreases related to settlements with taxing authorities (3,594 ) (123 ) (7,481 ) Reductions related to the lapse of statute of limitations (19,492 ) (2,831 ) (1,597 ) Unrecognized tax benefits at end of year $ 131,608 $ 152,581 $ 47,109

Parent Only Statements (Tables)

Parent Only Statements (Tables)	12 Months Ended
	Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Parent only Condensed Balance Sheets	Parent Only Condensed Balance Sheets December 31, 2017 2016 Assets Cash and cash equivalents $ 260,255 $ 292,277 Total investments in subsidiaries (primarily Sallie Mae Bank) 2,401,114 2,042,015 Tax indemnification receivable 168,011 259,532 Due from subsidiaries, net 37,521 31,834 Other assets 1,279 1,561 Total assets $ 2,868,180 $ 2,627,219 Liabilities and Equity Liabilities Long-term borrowings $ 196,539 $ — Income taxes payable, net 159,954 256,556 Payable due to Navient 10,575 2,823 Other liabilities 26,856 20,782 Total liabilities 393,924 280,161 Equity Preferred stock, par value $0.20 per share, 20 million shares authorized: Series A: 0 and 3.3 million shares issued, respectively, at stated value of $50 per share — 165,000 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: 443.5 million and 436.6 million shares issued, respectively 88,693 87,327 Additional paid-in capital 1,222,277 1,175,564 Accumulated other comprehensive income (loss) (net of tax expense (benefit) of $1,696 and ($5,364), respectively) 2,748 (8,671 ) Retained earnings 868,182 595,322 Total SLM Corporation stockholders’ equity before treasury stock 2,581,900 2,414,542 Less: Common stock held in treasury at cost: 11.1 million and 7.7 million shares, respectively (107,644 ) (67,484 ) Total equity 2,474,256 2,347,058 Total liabilities and equity $ 2,868,180 $ 2,627,219
Parent only Condensed Statements of Income	Parent Only Condensed Statements of Income Years Ended December 31, 2017 2016 2015 Interest income $ 5,497 $ 5,367 $ 6,414 Interest expense 8,170 — — Net interest income (2,673 ) 5,367 6,414 Non-interest income (loss) (33,956 ) 9,396 (239 ) Non-interest expenses 35,810 32,553 36,141 Loss before income tax benefit and equity in net income from subsidiaries (72,439 ) (17,790 ) (29,966 ) Income tax benefit (40,598 ) (2,839 ) (8,612 ) Equity in net income from subsidiaries (primarily Sallie Mae Bank) 320,775 265,278 295,638 Net income 288,934 250,327 274,284 Preferred stock dividends 15,714 21,204 19,595 Net income attributable to SLM Corporation common stock $ 273,220 $ 229,123 $ 254,689
Parent only Condensed Statements of Cash Flows	Parent Only Condensed Statements of Cash Flows Years Ended December 31, 2017 2016 2015 Cash flows from operating activities: Net income $ 288,934 $ 250,327 $ 274,284 Adjustments to reconcile net income to net cash provided by (used in) operating activities: Undistributed earnings of subsidiaries (320,775 ) (265,278 ) (295,638 ) Loss (income) on tax indemnification receivable 31,888 (12,283 ) (5,398 ) Amortization of unsecured debt upfront fees 596 — — Decrease (increase) in investment in subsidiaries, net 1,158 63,222 (103,602 ) Decrease in tax indemnification receivable 59,633 59,633 59,633 (Increase) decrease in due from subsidiaries, net (5,687 ) (10,438 ) 11,012 Increase in other assets (24,627 ) (8,972 ) (14,366 ) Decrease in income taxes payable, net (87,983 ) (54,175 ) (53,167 ) (Decrease) increase in payable due to entity that is a subsidiary of Navient (593 ) 553 (6,774 ) Increase in other liabilities 10,205 8,856 1,402 Total adjustments (336,185 ) (218,882 ) (406,898 ) Net cash (used in) provided by operating activities (47,251 ) 31,445 (132,614 ) Cash flows from investing activities: Net cash provided by (used in) investing activities — — — Cash flows from financing activities: Unsecured debt issued 197,000 — — Issuance costs for unsecured debt offering (1,057 ) — — Redemption of Series A Preferred Stock (165,000 ) — — Preferred stock dividends paid (15,714 ) (21,204 ) (19,595 ) Net cash provided by (used in) financing activities 15,229 (21,204 ) (19,595 ) Net (decrease) increase in cash and cash equivalents (32,022 ) 10,241 (152,209 ) Cash and cash equivalents at beginning of year 292,277 282,036 434,245 Cash and cash equivalents at end of year $ 260,255 $ 292,277 $ 282,036

Selected Quarterly Financial 48

Selected Quarterly Financial Information (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	2017 First Second Third Fourth (Dollars in thousands, except per share data) Quarter Quarter Quarter Quarter Net interest income $ 268,076 $ 269,893 $ 282,061 $ 309,191 Less: provisions for credit losses 25,296 50,215 54,930 55,324 Net interest income after provisions for credit losses 242,780 219,678 227,131 253,867 (Losses) gains on derivative and hedging activities, net (5,378 ) (3,609 ) 1,661 (940 ) Other income (loss) 11,346 10,629 4,455 (21,066 ) Total operating expenses 102,677 111,251 116,142 118,550 Acquired intangible asset amortization expense 117 117 117 118 Income tax expense 51,011 44,713 40,617 66,190 Net income 94,943 70,617 76,371 47,003 Preferred stock dividends 5,575 3,974 3,028 3,137 Net income attributable to SLM Corporation common stock $ 89,368 $ 66,643 $ 73,343 $ 43,866 Basic earnings per common share attributable to SLM Corporation (1) $ 0.21 $ 0.15 $ 0.17 $ 0.10 Diluted earnings per common share attributable to SLM Corporation (1) $ 0.20 $ 0.15 $ 0.17 $ 0.10 _____ (1) Basic and diluted earnings per common share attributable to SLM Corporation are computed independently for each of the quarters presented. Therefore, the sum of quarterly basic and diluted earnings per common share information may not equal annual basic and diluted earnings per common share. 2016 First Second Third Fourth (Dollars in thousands, except per share data) Quarter Quarter Quarter Quarter Net interest income $ 209,863 $ 212,766 $ 223,275 $ 245,434 Less: provisions for credit losses 32,602 41,793 41,784 43,226 Net interest income after provisions for credit losses 177,261 170,973 181,491 202,208 Gains on sales of loans, net — — — 230 (Losses) gains on derivative and hedging activities, net (354 ) 2,142 1,368 (4,114 ) Other income 21,028 13,683 21,598 13,235 Total operating expenses 92,885 94,777 99,709 98,036 Acquired intangible asset amortization expense 260 261 226 159 Income tax expense 38,875 34,555 47,557 43,122 Net income 65,915 57,205 56,965 70,242 Preferred stock dividends 5,139 5,243 5,316 5,506 Net income attributable to SLM Corporation common stock $ 60,776 $ 51,962 $ 51,649 $ 64,736 Basic earnings per common share attributable to SLM Corporation (1) $ 0.14 $ 0.12 $ 0.12 $ 0.15 Diluted earnings per common share attributable to SLM Corporation (1) $ 0.14 $ 0.12 $ 0.12 $ 0.15 _____ (1) Basic and diluted earnings per common share attributable to SLM Corporation are computed independently for each of the quarters presented. Therefore, the sum of quarterly basic and diluted earnings per common share information may not equal annual basic and diluted earnings per common share.

Organization and Business - Add

Organization and Business - Additional Information (Detail)	Apr. 30, 2014entityshares
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of publicly-traded entities | entity	2
Number of shares issued for each share prior to spin-off (in shares) | shares	1

Significant Accounting Polici50

Significant Accounting Policies - Additional Information (Detail)	3 Months Ended	4 Months Ended	12 Months Ended
	Mar. 31, 2017USD ($)	Apr. 29, 2014	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Apr. 30, 2014USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loan loss confirmation period (in years)			1 year
FFELP loan loss confirmation period (in years)			2 years
Loan delinquent period		90 days
Minimum days past due for spin off loan purchase			90 days
Period of hardship forbearance			6 months
Private education loans			$ 17,244,830,000	$ 14,113,409,000
Personal loans held at end of year			$ 393,700,000	$ 12,800,000
Interest rate reduction and forbearance usage (greater than)			3 months
Period of forbearance period to be classified as TDR			3 months
Period of forbearance			24 months
Period after grace period for forbearance allowance for loans			9 months
Forbearance period after grace period for loans			6 months
Percentage of loans granted forbearance (as a percentage)			66.00%	69.00%
Percentage of Private Education Loans related to borrowers inschool, grace or deferment (as a percentage)			27.00%	29.00%
Period after last payment contractually due private education loan considered to be delinquent			31 days
Percentage reimbursement on all qualifying default claims period two (as a percentage)			97.00%
Percentage reimbursement on all qualifying default claims period one (as a percentage)			98.00%
Percentage reimbursement on all qualifying default claims period three (as a percentage)			100.00%
Period of loss emergence to estimate credit losses incurred			2 years
Period of notification for withdrawal of deposits (less than or equal to)			7 days
Constant prepayment rate for Private Education Loans (in percentage)			5.94%	5.00%
Variable rate			1.05
Gains on sales of loans, net			$ 0	$ 230,000	$ 135,358,000
Asset balance related to securitization trust (as a percentage)			10.00%
Total amount of notional derivative contracts			$ 5,500,000,000
Excess tax benefit, amount	$ 200,000		8,500,000
Deferred taxes				9,180,000		$ 283,000,000
Tax indemnification receivable			168,011,000	259,532,000
Deferred tax asset discount			108,000,000
Remaining amount of indemnification			$ 35,000,000
Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan delinquent period			120 days
Split Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private education loans			$ 48,000,000
Navient
Accounts, Notes, Loans and Financing Receivable [Line Items]
Deferred taxes			37,000,000			283,000,000
Tax indemnification receivable				60,000,000		291,000,000
Deferred tax asset discount			25,000,000	25,000,000		27,000,000
Deferred tax liability			62,000,000			310,000,000
Deferred tax assets						310,000,000
Deferred tax asset discount						$ 19,000,000
Remaining amount of indemnification				35,000,000
Remaining balance of liability for uncertain tax positions			108
Additional Tax Positions
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase in tax receivable and income tax payable				120,000,000
Increase in other income and income tax expense				$ 9,000,000
CME
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total amount of notional derivative contracts			$ 4,800,000,000
Percent of total notional derivative contracts			87.60%
LCH
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total amount of notional derivative contracts			$ 700,000,000
Percent of total notional derivative contracts			12.40%

Cash and Cash Equivalents (Deta

Cash and Cash Equivalents (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Abstract]
Cash due from Federal Reserve Bank	$ 1,500,000,000	$ 1,900,000,000
Cash due from depository institutions	43,100,000	26,900,000
Outstanding cash equivalents	0	0
Interest income from term deposit facility	500,000	200,000
Funds on deposit under the Term Deposit Facility program	0	0
Average reserve balances with Federal Reserve	$ 0	$ 500,000

Investments - Amortized Cost an

Investments - Amortized Cost and Fair Value of Securities Available for Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available for sale:
Amortized Cost	$ 247,607	$ 211,406
Gross Unrealized Gains	650	929
Gross Unrealized Losses	(4,169)	(3,732)
Mortgage-backed securities	244,088	208,603
Mortgage-backed securities
Available for sale:
Amortized Cost	227,607	196,406
Gross Unrealized Gains	650	929
Gross Unrealized Losses	(3,210)	(3,042)
Mortgage-backed securities	225,047	194,293
Utah Housing Corporation bonds
Available for sale:
Amortized Cost	20,000	15,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(959)	(690)
Mortgage-backed securities	$ 19,041	$ 14,310

Investments - Gross Unrealized

Investments - Gross Unrealized Losses and Fair Value for Mortgage-Backed in Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Gross Unrealized Losses	$ (849)	$ (3,113)
12 months or more, Gross Unrealized Losses	(3,320)	(619)
Total, Gross Unrealized Losses	(4,169)	(3,732)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, Estimated Fair Value	82,279	143,859
12 months or more, Estimated Fair Value	124,618	10,885
Total, Estimated Fair Value	206,897	154,744
Mortgage-backed securities
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Gross Unrealized Losses	(772)	(2,423)
12 months or more, Gross Unrealized Losses	(2,438)	(619)
Total, Gross Unrealized Losses	(3,210)	(3,042)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, Estimated Fair Value	77,356	129,549
12 months or more, Estimated Fair Value	110,500	10,885
Total, Estimated Fair Value	187,856	140,434
Utah Housing Corporation bonds
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss [Abstract]
Less than 12 months, Gross Unrealized Losses	(77)	(690)
12 months or more, Gross Unrealized Losses	(882)	0
Total, Gross Unrealized Losses	(959)	(690)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, Estimated Fair Value	4,923	14,310
12 months or more, Estimated Fair Value	14,118	0
Total, Estimated Fair Value	$ 19,041	$ 14,310

Investments - Additional Inform

Investments - Additional Information (Details) $ in Thousands	Dec. 31, 2017USD ($)security	Dec. 31, 2016USD ($)security
Investment Holdings [Line Items]
Amortized Cost	$ 247,607	$ 211,406
Par value of mortgage-backed securities pledged to FRB	218,400	188,000
Mortgage-backed securities
Investment Holdings [Line Items]
Amortized Cost	$ 227,607	$ 196,406
Number of mortgage-backed securities with unrealized losses | security	62	48
Number of mortgage-backed securities | security	92	84
Utah Housing Corporation bonds
Investment Holdings [Line Items]
Amortized Cost	$ 20,000	$ 15,000
Ginnie Mae | Mortgage-backed securities
Investment Holdings [Line Items]
Amortized Cost	$ 110,200
Number of mortgage-backed securities with unrealized losses | security	31	21
Fannie Mae | Mortgage-backed securities
Investment Holdings [Line Items]
Amortized Cost	$ 70,800
Freddie Mac | Mortgage-backed securities
Investment Holdings [Line Items]
Amortized Cost	46,600
Aa3 Rating | Utah Housing Corporation bonds
Investment Holdings [Line Items]
Amortized Cost	$ 20,000

Investments - Maturity Table (D

Investments - Maturity Table (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 247,607	$ 211,406
Mortgage-backed securities	244,088	$ 208,603
Maturity 2,038
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	272
Mortgage-backed securities	293
Maturity 2,039
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,406
Mortgage-backed securities	3,606
Maturity 2,042
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,993
Mortgage-backed securities	10,487
Maturity 2,043
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	37,438
Mortgage-backed securities	37,534
Maturity 2,044
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	28,301
Mortgage-backed securities	28,206
Maturity 2,045
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	41,082
Mortgage-backed securities	40,484
Maturity 2,046
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	48,785
Mortgage-backed securities	47,771
Maturity 2,047
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	77,330
Mortgage-backed securities	$ 75,707

Loans Held for Investment - Add

Loans Held for Investment - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)payment	Dec. 31, 2016USD ($)	Jul. 01, 2006	Jun. 30, 2006	Sep. 30, 1993
Finance Receivable Transferred To Held For Sale [Line Items]
Percent of private loans indexed to LIBOR (as a percentage)	77.00%	81.00%
Tier 1 of government guarantee			97.00%
Tier 2 of government guarantee				98.00%
Tier 3 of government guarantee					100.00%
Estimated weighted average life of student loans	5 years 6 months	6 years
Number of payments to qualify for Private Education Loan program | payment	3
Period of interest rate reduction	24 months
Period of loans past due that have accrued interest	90 days
Loans in nonaccrual status	$ 0	$ 0
Percentage of loans concentrated in major states	40.40%	40.30%
Percentage of aggregate outstanding loans held for investment	5.00%
FFELP Loans
Finance Receivable Transferred To Held For Sale [Line Items]
Ninety or more days delinquent	$ 66,900,000	$ 67,500,000
Private Education Loans
Finance Receivable Transferred To Held For Sale [Line Items]
Ninety or more days delinquent	37,600,000	24,200,000
Private Education Loans
Finance Receivable Transferred To Held For Sale [Line Items]
Loans pledged to borrower in custody	$ 2,700,000,000	$ 2,700,000,000

Loans Held for Investment - Stu

Loans Held for Investment - Student Loan Portfolio by Program (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Receivables [Abstract]
Private Education Loans	$ 17,432,167	$ 14,251,675
Deferred origination costs	56,378	44,206
Allowance for loan losses	(243,715)	(182,472)
Total Private Education Loans, net	17,244,830	14,113,409
FFELP Loans	927,660	1,010,908
Unamortized acquisition costs, net	2,631	2,941
Allowance for loan losses	(1,132)	(2,171)
Total FFELP Loans, net	929,159	1,011,678
Personal Loans	400,280	12,893
Allowance for loan losses	(6,628)	(58)
Total Personal Loans, net	393,652	12,835
Loans held for investment, net	$ 18,567,641	$ 15,137,922

Loans Held for Investment - S58

Loans Held for Investment - Student Loan Portfolio Average Balances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Receivables [Abstract]
Average balance of Private Education Loans	$ 16,176,351	$ 12,747,756	$ 9,819,053
Average Balance, FFELP Loans	970,738	1,063,325	1,179,723
Average Balance of Personal Loans	112,644	710	0
Average Balance, Total portfolio	$ 17,259,733	$ 13,811,791	$ 10,998,776
Weighted Average Interest Rate, Private Education Loans	8.43%	8.02%	7.93%
Weighted Average Interest Rate, FFELP Loans	3.91%	3.53%	3.26%
Weighted Average Interest Rate of Personal Loans	9.90%	8.53%	0.00%

Loans Held for Investment - By

Loans Held for Investment - By Region (Details)	Dec. 31, 2017	Dec. 31, 2016
Loans held for investment by Region [Line Items]
Percentage of Loans concentrated in major states	40.40%	40.30%
New York
Loans held for investment by Region [Line Items]
Percentage of Loans held in state	10.50%	10.30%
California
Loans held for investment by Region [Line Items]
Percentage of Loans held in state	9.30%	9.40%
Pennsylvania
Loans held for investment by Region [Line Items]
Percentage of Loans held in state	8.50%	8.40%
New Jersey
Loans held for investment by Region [Line Items]
Percentage of Loans held in state	6.90%	6.90%
Illinois
Loans held for investment by Region [Line Items]
Percentage of Loans held in state	5.20%	5.30%

Allowance for Loan Losses - All

Allowance for Loan Losses - Allowance for Credit Losses and Recorded Investments in Loans (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)charge_off	Dec. 31, 2016USD ($)charge_off	Dec. 31, 2015USD ($)charge_off
Allowance for Loan Losses
Beginning balance	$ 184,701	$ 112,507	$ 83,842
Total provision	185,595	159,397	88,349
Charge-offs	(131,596)	(91,551)	(57,939)
Recoveries	17,646	10,382	5,820
Net charge-offs	(113,950)	(81,169)	(52,119)
Student loan sales	(4,871)	(6,034)	(7,565)
Ending Balance	251,475	184,701	112,507
Allowance:
Ending balance: individually evaluated for impairment	94,682	86,930	43,480
Ending balance: collectively evaluated for impairment	156,793	97,771	69,027
Loans:
Ending balance: individually evaluated for impairment	990,351	612,606	265,831
Ending balance: collectively evaluated for impairment	17,769,756	14,662,871	11,446,269
FFELP Loans
Allowance for Loan Losses
Beginning balance	2,171	3,691	5,268
Total provision	(85)	(172)	1,005
Charge-offs	(954)	(1,348)	(2,582)
Recoveries	0	0	0
Net charge-offs	(954)	(1,348)	(2,582)
Student loan sales	0	0	0
Ending Balance	1,132	2,171	3,691
Allowance:
Ending balance: individually evaluated for impairment	0	0	0
Ending balance: collectively evaluated for impairment	1,132	2,171	3,691
Loans:
Ending balance: individually evaluated for impairment	0	0	0
Ending balance: collectively evaluated for impairment	$ 927,660	$ 1,010,908	$ 1,115,663
Net charge-offs as a percentage of average loans in repayment	0.13%	0.17%	0.30%
Allowance as a percentage of the ending total loan balance	0.12%	0.21%	0.33%
Allowance as a percentage of the ending loans in repayment	0.15%	0.28%	0.45%
Allowance coverage of net charge-offs | charge_off	1.19	1.61	1.43
Ending total loans, gross	$ 927,660	$ 1,010,908	$ 1,115,663
Average loans in repayment	745,039	793,203	857,359
Ending loans in repayment	746,456	786,332	813,815
Private Education Loans
Allowance for Loan Losses
Beginning balance	182,472	108,816	78,574
Total provision	178,542	159,511	87,344
Charge-offs	(130,063)	(90,203)	(55,357)
Recoveries	17,635	10,382	5,820
Net charge-offs	(112,428)	(79,821)	(49,537)
Student loan sales	(4,871)	(6,034)	(7,565)
Ending Balance	243,715	182,472	108,816
Allowance:
Ending balance: individually evaluated for impairment	94,682	86,930	43,480
Ending balance: collectively evaluated for impairment	149,033	95,542	65,336
Loans:
Ending balance: individually evaluated for impairment	990,351	612,606	265,831
Ending balance: collectively evaluated for impairment	$ 16,441,816	$ 13,639,069	$ 10,330,606
Net charge-offs as a percentage of average loans in repayment	1.03%	0.96%	0.82%
Allowance as a percentage of the ending total loan balance	1.40%	1.28%	1.03%
Allowance as a percentage of the ending loans in repayment	2.00%	1.88%	1.57%
Allowance coverage of net charge-offs | charge_off	2.17	2.29	2.20
Ending total loans, gross	$ 17,432,167	$ 14,251,675	$ 10,596,437
Average loans in repayment	10,881,058	8,283,036	6,031,741
Ending loans in repayment	12,206,033	9,709,758	6,927,266
Personal Loans
Allowance for Loan Losses
Beginning balance	58	0
Total provision	7,138	58
Charge-offs	(579)	0
Recoveries	11	0
Net charge-offs	(568)	0
Student loan sales	0	0
Ending Balance	6,628	58	$ 0
Allowance:
Ending balance: individually evaluated for impairment	0	0
Ending balance: collectively evaluated for impairment	6,628	58
Loans:
Ending balance: individually evaluated for impairment	0	0
Ending balance: collectively evaluated for impairment	$ 400,280	$ 12,894
Net charge-offs as a percentage of average loans in repayment	0.47%	0.00%
Allowance as a percentage of the ending total loan balance	1.66%	0.00%
Allowance as a percentage of the ending loans in repayment	1.66%	0.00%
Allowance coverage of net charge-offs | charge_off	11.67	0
Ending total loans, gross	$ 400,280	$ 0
Average loans in repayment	119,606	0
Ending loans in repayment	$ 400,280	$ 0

Allowance for Loan Losses - Add

Allowance for Loan Losses - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Jul. 01, 2006
Schedule Of Allowance For Credit Losses And Recorded Investment In Financing Receivables Table [Line Items]
Period after grace period for forbearance allowance for loans	9 months
Forbearance period after grace period for loans	6 months
Period of forbearance period to be classified as TDR	3 months
Period of forbearance	24 months
Percentage of loans granted forbearance (as a percentage)	66.00%	69.00%
Criteria for loans to be considered as nonperforming	90 days
Tier 1 of government guarantee (at least)			97.00%
TDR payment default period	60 days
Period of loans past due that have accrued interest	90 days
FFELP Loans
Schedule Of Allowance For Credit Losses And Recorded Investment In Financing Receivables Table [Line Items]
Tier 1 of government guarantee (at least)	97.00%

Allowance for Loan Losses - Rec

Allowance for Loan Losses - Recorded Investment, Unpaid Principal Balance and Related Allowance for TDR Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Receivables [Abstract]
TDR Loans, Recorded Investment	$ 1,007,141	$ 620,991
TDR Loans, Unpaid Principal Balance	990,351	612,606
TDR Loans, Allowance	$ 94,682	$ 86,930

Allowance for Loan Losses - Ave

Allowance for Loan Losses - Average Recorded Investment and Interest Income Recognized for TDR (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Receivables [Abstract]
TDR Loans, Average Recorded Investment	$ 822,145	$ 422,527	$ 174,087
TDR Loans, Interest Income Recognized	$ 61,119	$ 30,700	$ 14,081

Allowance for Loan Losses - Age

Allowance for Loan Losses - Age Analysis of Past Due Loan Delinquencies (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
TDR loans in repayment and percentage of each status:
Private Education Loans allowance for losses	$ (251,475)	$ (184,701)	$ (112,507)	$ (83,842)
Student Loan | Consumer Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans in in-school/grace/deferment	4,757,732	4,189,955	3,427,964
Loans in forbearance	468,402	351,962	241,207
TDR loans in repayment and percentage of each status:
Loans current	11,911,128	9,509,394	6,773,095
Total TDR loans in repayment	$ 12,206,033	$ 9,709,758	$ 6,927,266
Loans current, in percentage	97.60%	97.90%	97.80%
Loans in repayment, in percentage	100.00%	100.00%	100.00%
Total TDR loans, gross	$ 17,432,167	$ 14,251,675	$ 10,596,437
Private Education Loans deferred origination costs	56,378	44,206	27,884
Total Private Education Loans	17,488,545	14,295,881	10,624,321
Private Education Loans allowance for losses	(243,715)	(182,472)	(108,816)
Percentage of Private Education Loans in repayment	$ 17,244,830	$ 14,113,409	$ 10,515,505
Percentage of Private Education Loans in repayment	70.00%	68.10%	65.40%
Delinquencies as a percentage of Private Education Loans in repayment	2.40%	2.10%	2.20%
Loans in forbearance as a percentage of Private Education Loans in repayment and forbearance	3.70%	3.50%	3.40%
Student Loan | Consumer Portfolio Segment | Loans delinquent 31-60 days
TDR loans in repayment and percentage of each status:
Loans delinquent	$ 179,002	$ 124,773	$ 91,129
Loans delinquent (in percentage)	1.50%	1.30%	1.30%
Student Loan | Consumer Portfolio Segment | Loans delinquent 61-90 days
TDR loans in repayment and percentage of each status:
Loans delinquent	$ 78,292	$ 51,423	$ 42,048
Loans delinquent (in percentage)	0.60%	0.50%	0.60%
Student Loan | Consumer Portfolio Segment | Loans delinquent greater than 90 days
TDR loans in repayment and percentage of each status:
Loans delinquent	$ 37,611	$ 24,168	$ 20,994
Loans delinquent (in percentage)	0.30%	0.30%	0.30%
Troubled Debt Restructured Loans | Student Loan | Consumer Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans in in-school/grace/deferment	$ 51,745	$ 24,185
Loans in forbearance	69,652	71,851
TDR loans in repayment and percentage of each status:
Loans current	774,222	462,187
Total TDR loans in repayment	$ 868,954	$ 516,570
Loans current, in percentage	89.10%	89.50%
Loans in repayment, in percentage	100.00%	100.00%
Total TDR loans, gross	$ 990,351	$ 612,606
Troubled Debt Restructured Loans | Student Loan | Consumer Portfolio Segment | Loans delinquent 31-60 days
TDR loans in repayment and percentage of each status:
Loans delinquent	$ 48,377	$ 28,452
Loans delinquent (in percentage)	5.60%	5.50%
Troubled Debt Restructured Loans | Student Loan | Consumer Portfolio Segment | Loans delinquent 61-90 days
TDR loans in repayment and percentage of each status:
Loans delinquent	$ 28,778	$ 17,326
Loans delinquent (in percentage)	3.30%	3.40%
Troubled Debt Restructured Loans | Student Loan | Consumer Portfolio Segment | Loans delinquent greater than 90 days
TDR loans in repayment and percentage of each status:
Loans delinquent	$ 17,577	$ 8,605
Loans delinquent (in percentage)	2.00%	1.60%

Allowance for Loan Losses - Mod

Allowance for Loan Losses - Modified Loan Accounts for TDR (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Receivables [Abstract]
Modified Loans	$ 498,812	$ 398,324	$ 244,890
Charge-offs	48,469	24,628	10,877
Payment-Default	$ 92,532	$ 64,811	$ 51,602

Allowance for Loan Losses - Pri

Allowance for Loan Losses - Private Education Loan Portfolio Stratified by Key Credit Quality Indicators (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 17,432,167	$ 14,251,675
Consumer Portfolio Segment | Student Loan | With cosigner
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 15,658,539	$ 12,816,512
Private Education Loans with cosigner in percent	90.00%	90.00%
Consumer Portfolio Segment | Student Loan | Without cosigner
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 1,773,628	$ 1,435,163
Private Education Loans without cosigner in percent	10.00%	10.00%
Consumer Portfolio Segment | Student Loan | Cosigners
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 17,432,167	$ 14,251,675
Total in percent	100.00%	100.00%
Consumer Portfolio Segment | Student Loan | School Type/FICO Scores
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 17,432,167	$ 14,251,675
Total in percent	100.00%	100.00%
Consumer Portfolio Segment | Student Loan | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 17,432,167	$ 14,251,675
Total in percent	100.00%	100.00%
Seasoning based on monthly scheduled payments due from 1-12 payments, in percent	24.00%	26.00%
Seasoning based on monthly scheduled payments due from 13 - 24 payments, in percent	19.00%	20.00%
Seasoning based on monthly scheduled payments due from 25 - 36 payments, in percent	14.00%	13.00%
Seasoning based on monthly scheduled payments due from 37 - 48 payments, in percent	9.00%	7.00%
Seasoning based on monthly scheduled payments due from more than 48 payments, in percent	7.00%	5.00%
Seasoning - based on monthly scheduled payments due from not yet in repayment, in percent	27.00%	29.00%
Consumer Portfolio Segment | Personal Loans | School Type/FICO Scores
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 400,280	$ 12,894
Total in percent	100.00%	100.00%
Consumer Portfolio Segment | Personal Loans | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 400,280	$ 12,894
Total in percent	100.00%	100.00%
Seasoning based on monthly scheduled payments due from 1-12 payments, in percent	100.00%	100.00%
Seasoning based on monthly scheduled payments due from 13 - 24 payments, in percent	0.00%	0.00%
Seasoning based on monthly scheduled payments due from 25 - 36 payments, in percent	0.00%	0.00%
Seasoning based on monthly scheduled payments due from 37 - 48 payments, in percent	0.00%	0.00%
Seasoning based on monthly scheduled payments due from more than 48 payments, in percent	0.00%	0.00%
FICO score less than 670 | Consumer Portfolio Segment | Student Loan | School Type/FICO Scores
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 1,153,591	$ 920,132
Private Education Loans at origination	6.00%	6.00%
FICO score less than 670 | Consumer Portfolio Segment | Personal Loans | School Type/FICO Scores
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 32,156	$ 1,189
Private Education Loans at origination	8.00%	9.00%
FICO score 670-699 | Consumer Portfolio Segment | Student Loan | School Type/FICO Scores
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 2,596,959	$ 2,092,722
Private Education Loans at origination	15.00%	15.00%
FICO score 670-699 | Consumer Portfolio Segment | Personal Loans | School Type/FICO Scores
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 114,731	$ 3,139
Private Education Loans at origination	29.00%	24.00%
FICO score 700-749 | Consumer Portfolio Segment | Student Loan | School Type/FICO Scores
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 5,714,554	$ 4,639,958
Private Education Loans at origination	33.00%	33.00%
FICO score 700-749 | Consumer Portfolio Segment | Personal Loans | School Type/FICO Scores
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 182,025	$ 5,678
Private Education Loans at origination	45.00%	44.00%
FICO score greater than 750 | Consumer Portfolio Segment | Student Loan | School Type/FICO Scores
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 7,967,063	$ 6,598,863
Private Education Loans at origination	46.00%	46.00%
FICO score greater than 750 | Consumer Portfolio Segment | Personal Loans | School Type/FICO Scores
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 71,368	$ 2,888
Private Education Loans at origination	18.00%	23.00%
1-12 payments | Consumer Portfolio Segment | Student Loan | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 4,256,592	$ 3,737,110
1-12 payments | Consumer Portfolio Segment | Personal Loans | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	400,280	12,894
13-24 payments | Consumer Portfolio Segment | Student Loan | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	3,229,465	2,841,107
13-24 payments | Consumer Portfolio Segment | Personal Loans | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	0	0
25-36 payments | Consumer Portfolio Segment | Student Loan | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	2,429,238	1,839,764
25-36 payments | Consumer Portfolio Segment | Personal Loans | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	0	0
37-48 payments | Consumer Portfolio Segment | Student Loan | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	1,502,327	917,633
37-48 payments | Consumer Portfolio Segment | Personal Loans | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	0	0
More than 48 payments | Consumer Portfolio Segment | Student Loan | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	1,256,813	726,106
More than 48 payments | Consumer Portfolio Segment | Personal Loans | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	0	0
Not yet in repayment | Consumer Portfolio Segment | Student Loan | Seasoning
Accounts, Notes, Loans and Financing Receivable [Line Items]
Private Education Loans	$ 4,757,732	$ 4,189,955

Allowance for Loan Losses - Acc

Allowance for Loan Losses - Accrued Interest Receivable (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Receivables [Abstract]
Total Interest Receivable	$ 951,138	$ 739,847
Greater Than 90 Days Past Due	1,372	845
Allowance for Uncollectible Interest	$ 4,664	$ 2,898

Premises and Equipment, Net - S

Premises and Equipment, Net - Schedule of Premises and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 144,231	$ 136,207
Accumulated depreciation	(54,483)	(49,144)
Premises and equipment, net	89,748	87,063
Land and land improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	12,356	12,574
Buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	61,409	60,919
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	15,261	15,026
Software
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 55,205	$ 47,688

Premises and Equipment, Net - N

Premises and Equipment, Net - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Depreciation of premises and equipment	$ 11,171	$ 9,592	$ 7,437

Deposits - Summary of Total Dep

Deposits - Summary of Total Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deposits [Abstract]
Deposits - interest bearing	$ 15,504,330	$ 13,434,990
Deposits - non-interest bearing	1,053	677
Total deposits	$ 15,505,383	$ 13,435,667

Deposits - Additional Informati

Deposits - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deposits [Abstract]
Deposits	$ 15,505,383	$ 13,435,667
Brokered deposits	8,200,000	7,100,000
Retail and other deposits	7,300,000	6,300,000
Aggregate of deposits of individual depositors	5,500,000	5,400,000
Brokered deposit placement fee	9,400	10,100	$ 10,500
Third party broker fees paid	12,200	4,400	$ 4,100
Deposits exceeding FDIC insurance limits	395,500	304,500
Accrued interest on deposits	$ 27,800	$ 18,900

Deposits - Interest Bearing Dep

Deposits - Interest Bearing Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Interest-bearing Deposit Liabilities, Domestic, by Component [Abstract]
Money market	$ 7,731,966	$ 7,129,404
Savings	738,243	834,521
Certificates of deposit	7,034,121	5,471,065
Deposits - interest bearing	$ 15,504,330	$ 13,434,990
Year-End Weighted Average Stated Rate
Money market	1.80%	1.22%
Savings	1.10%	0.84%
Certificates of deposit	1.93%	1.41%

Deposits - Certificates of Depo

Deposits - Certificates of Deposits Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Time Deposits, Fiscal Year Maturity [Abstract]
One year or less	$ 3,716,183	$ 2,565,246
After one year to two years	1,550,130	1,364,812
After two years to three years	806,488	936,125
After three years to four years	447,592	225,245
After four years to five years	445,884	379,637
After five years	67,844	0
Total	$ 7,034,121	$ 5,471,065

Borrowings - Secured Borrowings

Borrowings - Secured Borrowings (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Secured borrowings:
Short-Term	$ 0	$ 0
Long-Term	3,275,270,000	2,167,979,000
Total	3,275,270,000	2,167,979,000
ABCP borrowings
Secured borrowings:
Short-Term	0	0
Unsecured borrowings
Secured borrowings:
Short-Term	0	0
Long-Term	196,539,000	0
Total	196,539,000	0
Secured borrowings
Secured borrowings:
Short-Term	0	0
Long-Term	3,078,731,000	2,167,979,000
Total	3,078,731,000	2,167,979,000
Secured borrowings | Private Education Loan term securitizations
Secured borrowings:
Short-Term	0	0
Long-Term	3,078,731,000	2,167,979,000
Total	3,078,731,000	2,167,979,000
Secured borrowings | ABCP borrowings
Secured borrowings:
Short-Term	0	0
Long-Term	0	0
Total	$ 0	$ 0

Borrowings - Additional (Detail

Borrowings - Additional (Details) - USD ($)

Feb. 21, 2018

Nov. 08, 2017

Feb. 22, 2017

Feb. 08, 2017

Oct. 12, 2016

Jul. 21, 2016

May 26, 2016

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Apr. 05, 2017

Oct. 27, 2015

Apr. 23, 2015

Debt Instrument [Line Items]

Amount drawn and outstanding under ABCP facility

$ 0

$ 0

Total Issued

1,448,000,000

1,782,000,000

Unsecured debt issued

$ 197,000,000

$ 0

$ 0

Estimated weighted average life of student loans

5 years 6 months

6 years

Discretionary uncommitted federal funds line of credit

$ 125,000,000

Lendable value of collateral

2,600,000,000

ABCP borrowings

Debt Instrument [Line Items]

Amount drawn and outstanding under ABCP facility

$ 0

$ 0

Contractual maturity related to ABCP facility

2 years

Revolving period of contractual maturity

1 year

Amortization period of contractual maturity

1 year

Private Education Loans

Debt Instrument [Line Items]

Private education loan term accounted for as a secured financing

$ 676,000,000

$ 772,000,000

$ 674,000,000

$ 657,000,000

$ 551,000,000

Ownership interest percentage on asset-backed financing

100.00%

100.00%

Loans sold to third parties

$ 701,000,000

$ 738,000,000

Unsecured debt issued

$ 674,000,000

$ 768,000,000

Class B Notes

Debt Instrument [Line Items]

Ownership interest percentage on asset-backed financing

100.00%

100.00%

Ownership interest amount of securitized or asset backed loan

$ 50,000,000

$ 50,000,000

Residual Certificates

Debt Instrument [Line Items]

Ownership interest percentage on asset-backed financing

100.00%

100.00%

Private Education Loans, Class A

Debt Instrument [Line Items]

Loans sold to third parties

$ 607,000,000

$ 501,000,000

Unsecured debt issued

$ 607,000,000

$ 501,000,000

Class A Notes

Debt Instrument [Line Items]

Estimated weighted average life of student loans

4 years 4 days

4 years 4 days

Private Education Loans, 2017 Term B

Debt Instrument [Line Items]

Loans pledged as collateral

$ 698,000,000

Private Education Loans, 2017 Term A

Debt Instrument [Line Items]

Loans pledged as collateral

733,000,000

Private Education Loans, 2016 Term A

Debt Instrument [Line Items]

Loans pledged as collateral

501,000,000

Private Education Loans, 2016 Term B

Debt Instrument [Line Items]

Loans pledged as collateral

$ 605,000,000

Class C Notes

Debt Instrument [Line Items]

Ownership interest percentage on asset-backed financing

100.00%

Loans sold to third parties

$ 674,000,000

Unsecured debt issued

$ 673,000,000

Class A and B Notes

Debt Instrument [Line Items]

Estimated weighted average life of student loans

4 years 26 days

4 years 3 months 8 days

4 years 3 months 7 days

Private Education Loans, 2016 Term C

Debt Instrument [Line Items]

Loans pledged as collateral

$ 612,000,000

London Interbank Offered Rate (LIBOR) | Class A Notes

Debt Instrument [Line Items]

Basis spread on variable rate

1.36%

1.38%

London Interbank Offered Rate (LIBOR) | Class A and B Notes

Debt Instrument [Line Items]

Basis spread on variable rate

0.80%

0.93%

1.15%

Commercial Paper | ABCP borrowings

Debt Instrument [Line Items]

Private education loan funding

$ 750,000,000

Ownership Interest Percentage

100.00%

Commercial Paper | London Interbank Offered Rate (LIBOR) | ABCP borrowings

Debt Instrument [Line Items]

Basis spread on variable rate

0.85%

Minimum | Commercial Paper | ABCP borrowings

Debt Instrument [Line Items]

Unused borrowing capacity fee (as a percent)

0.35%

Maximum | Commercial Paper | ABCP borrowings

Debt Instrument [Line Items]

Unused borrowing capacity fee (as a percent)

0.45%

Unsecured Debt

Debt Instrument [Line Items]

Amount drawn and outstanding under ABCP facility

$ 0

$ 0

Unsecured Debt | Senior Unsecured Notes Due April 5, 2022

Debt Instrument [Line Items]

Total Issued

$ 197,000,000

$ 200,000,000

Interest rate

5.125%

Subsequent Event | Commercial Paper | ABCP borrowings

Debt Instrument [Line Items]

Private education loan funding

$ 750,000,000

Subsequent Event | Commercial Paper | London Interbank Offered Rate (LIBOR) | ABCP borrowings

Debt Instrument [Line Items]

Basis spread on variable rate

0.85%

Subsequent Event | Minimum | Commercial Paper | ABCP borrowings

Debt Instrument [Line Items]

Unused borrowing capacity fee (as a percent)

0.35%

Subsequent Event | Maximum | Commercial Paper | ABCP borrowings

Debt Instrument [Line Items]

Unused borrowing capacity fee (as a percent)

0.45%

Borrowings - Short Term Borrowi

Borrowings - Short Term Borrowings (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Short-term borrowings:
Short-Term	$ 0	$ 0
Maximum outstanding at any month end	300,000,000	526,500,000
ABCP Facility
Short-term borrowings:
Short-Term	$ 0	$ 0
Weighted Average Interest Rate	0.00%	0.00%
Average Balance	$ 81,370,000	$ 229,719,000
Weighted Average Interest Rate	6.09%	2.61%

Borrowings - Long Term Borrowin

Borrowings - Long Term Borrowings (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Line of Credit Facility [Line Items]
Long-term borrowings	$ 3,275,270	$ 2,167,979
Weighted Average Interest Rate	2.71%	2.15%
Average Balance	$ 2,843,593	$ 1,236,045
Floating rate borrowings
Line of Credit Facility [Line Items]
Long-term borrowings	$ 1,512,970	$ 1,175,819
Weighted Average Interest Rate	2.32%	1.71%
Average Balance	$ 1,422,856	$ 687,580
Fixed rate borrowings
Line of Credit Facility [Line Items]
Long-term borrowings	$ 1,762,300	$ 992,160
Weighted Average Interest Rate	3.04%	2.68%
Average Balance	$ 1,420,737	$ 548,465

Borrowings - Secured Financing

Borrowings - Secured Financing (Details) - USD ($)	Feb. 28, 2017	Oct. 31, 2016	Jul. 31, 2016	May 31, 2016	Nov. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total Issued						$ 1,448,000,000	$ 1,782,000,000
Total loans and accrued interest amount securitized at inception						$ 1,606,804,000	$ 2,107,042,000
Issuance 2016-A
Debt Instrument [Line Items]
Total Issued				$ 501,000,000
Weighted Average Life (in years)				4 years 5 days
Issuance 2016-B
Debt Instrument [Line Items]
Total Issued			$ 607,000,000
Weighted Average Life (in years)			4 years 5 days
Issuance 2016-C
Debt Instrument [Line Items]
Total Issued		$ 674,000,000
Weighted Average Life (in years)		4 years 2 months 36 days
Issuance 2017-A
Debt Instrument [Line Items]
Total Issued	$ 772,000,000
Weighted Average Life (in years)	4 years 2 months 36 days
Derivative basis spread on variable rate	0.93%
Issuance 2017-B
Debt Instrument [Line Items]
Total Issued					$ 676,000,000
Weighted Average Life (in years)					4 years 25 days
Derivative basis spread on variable rate					0.80%
London Interbank Offered Rate (LIBOR) | Issuance 2016-A
Debt Instrument [Line Items]
Derivative basis spread on variable rate				1.38%
London Interbank Offered Rate (LIBOR) | Issuance 2016-B
Debt Instrument [Line Items]
Derivative basis spread on variable rate			1.36%
London Interbank Offered Rate (LIBOR) | Issuance 2016-C
Debt Instrument [Line Items]
Derivative basis spread on variable rate		1.15%

Borrowings - Variable Interest

Borrowings - Variable Interest Entity (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Debt Outstanding
Short-Term	$ 0	$ 0
Long-Term	3,275,270,000	2,167,979,000
Total	3,275,270,000	2,167,979,000
Carrying Amount of Assets Securing Debt Outstanding
Restricted Cash	101,836,000	53,717,000
Other assets	84,853,000	52,153,000
ABCP Facility
Debt Outstanding
Short-Term	0	0
Variable Interest Entity, Primary Beneficiary
Debt Outstanding
Short-Term	0	0
Long-Term	3,078,731,000	2,167,979,000
Total	3,078,731,000	2,167,979,000
Carrying Amount of Assets Securing Debt Outstanding
Loans	3,691,024,000	2,562,156,000
Restricted Cash	96,983,000	44,617,000
Other assets	240,369,000	160,783,000
Total	4,028,376,000	2,767,556,000
Variable Interest Entity, Primary Beneficiary | Private Education Loan term securitizations
Debt Outstanding
Short-Term	0	0
Long-Term	3,078,731,000	2,167,979,000
Total	3,078,731,000	2,167,979,000
Carrying Amount of Assets Securing Debt Outstanding
Loans	3,691,024,000	2,562,156,000
Restricted Cash	95,966,000	44,617,000
Other assets	240,208,000	160,783,000
Total	4,027,198,000	2,767,556,000
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	1,017,000	0
Other assets	161,000	0
Total	$ 1,178,000	$ 0

Private Education Loan Term S80

Private Education Loan Term Securitizations Private Education Loan Term Securitizations (Details) - Private Education Loans - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Jun. 30, 2015	Oct. 27, 2015	Apr. 23, 2015
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale [Line Items]
Loans sold to third parties			$ 701	$ 738
Pre-tax gain on sale of loans	$ 58	$ 77
Percentage premium of private education loan term	7.80%	10.40%

Derivative Financial Instrume81

Derivative Financial Instruments - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Total amount of notional derivative contracts	$ 5,500,000
Net positive exposure	19,600	$ 44,600
Estimated reclassification of AOCI to interest expense	1,800
Cash collateral (held) pledged	0	0
Cash collateral held relative to derivative exposure	0	1,000
Cash collateral pledged	21,600	49,100
CME
Derivative [Line Items]
Total amount of notional derivative contracts	$ 4,800,000
Percentage of total notional derivative contracts	87.60%
LCH
Derivative [Line Items]
Total amount of notional derivative contracts	$ 700,000
Percentage of total notional derivative contracts	12.40%
Interest Rate Swaps
Derivative [Line Items]
Total amount of notional derivative contracts	$ 5,459,075	5,177,388
Net position	(1,772)	(18,129)
Fair Value | Designated as Hedging Instrument
Derivative [Line Items]
Net position	19,800	30,000
Fair Value | Interest Rate Swaps | Designated as Hedging Instrument
Derivative [Line Items]
Total amount of notional derivative contracts	3,062,849	3,628,062
Derivative instruments	1,800	18,100
Decrease in fair value of collateral	3,500
Variation margin	19,900
Net position	630	$ (2,590)
Fair Value | Contracts Other Than Chicago Mercantile Exchange | Designated as Hedging Instrument
Derivative [Line Items]
Decrease in fair value of collateral	3,500
Variation margin	25,400
Cash collateral (held) pledged	$ 32,100

Derivative Financial Instrume82

Derivative Financial Instruments - Impact of Derivatives on Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Derivative Assets	$ 812	$ 7,808
Interest Rate Swaps
Derivatives, Fair Value [Line Items]
Derivative Assets	812	7,808
Derivative Liabilities	(2,584)	(25,937)
Total net derivatives	(1,772)	(18,129)
Trading | Interest Rate Swaps
Derivatives, Fair Value [Line Items]
Derivative Assets	182	0
Derivative Liabilities	0	(1,076)
Total net derivatives	182	(1,076)
Cash Flow | Designated as Hedging Instrument | Interest Rate Swaps
Derivatives, Fair Value [Line Items]
Derivative Assets	0	0
Derivative Liabilities	(2,584)	(14,463)
Total net derivatives	(2,584)	(14,463)
Fair Value | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Total net derivatives	19,800	30,000
Fair Value | Designated as Hedging Instrument | Interest Rate Swaps
Derivatives, Fair Value [Line Items]
Derivative Assets	630	7,808
Derivative Liabilities	0	(10,398)
Total net derivatives	$ 630	$ (2,590)

Derivative Financial Instrume83

Derivative Financial Instruments - Offsetting Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Assets
Gross position	$ 812	$ 7,808
Impact of master netting agreement	(812)	(7,808)
Derivative values with impact of master netting agreements (as carried on balance sheet)	0	0
Cash collateral (held) pledged	0	0
Net position	0	0
Other Liabilities
Cash collateral (held) pledged	21,600	49,100
Other Liabilities
Other Liabilities
Gross position	(2,584)	(25,937)
Impact of master netting agreement	812	7,808
Derivative values with impact of master netting agreements (as carried on balance sheet)	(1,772)	(18,129)
Cash collateral (held) pledged	21,586	48,134
Net position	$ 19,814	$ 30,005

Derivative Financial Instrume84

Derivative Financial Instruments - Notional Values (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Notional Values	$ 5,500,000
Interest Rate Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Notional Values	5,459,075	$ 5,177,388
Interest Rate Swaps | Trading
Derivative Instruments, Gain (Loss) [Line Items]
Notional Values	987,577	494,638
Interest Rate Swaps | Cash Flow | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional Values	1,408,649	1,054,688
Interest Rate Swaps | Fair Value | Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Notional Values	$ 3,062,849	$ 3,628,062

Derivative Financial Instrume85

Derivative Financial Instruments - Impact of Derivatives on Consolidated Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Trading
Total	$ (940)	$ 1,661	$ (3,609)	$ (5,378)	$ (4,114)	$ 1,368	$ 2,142	$ (354)
Interest Rate Swaps
Trading
Total									$ (11,167)	$ 9,188	$ 13,765
Interest Rate Swaps | Designated as Hedging Instrument | Fair Value
Fair Value Hedges
Hedge ineffectiveness (losses) gains recorded in earnings									(4,557)	(1,035)	2,695
Realized gains recorded in interest expense									8,286	27,810	29,940
Trading
Total									3,729	26,775	32,635
Interest Rate Swaps | Designated as Hedging Instrument | Cash Flow
Cash Flow Hedges
Hedge ineffectiveness losses recorded in earnings									53	(1,579)	(1,427)
Realized losses recorded in interest expense									(11,187)	(17,665)	(21,475)
Trading
Total									(11,134)	(19,244)	(22,902)
Interest Rate Swaps | Trading
Trading
Interest reclassification									(69)	2,170	3,451
Realized gains (losses) recorded in earnings									(3,693)	(513)	581
Total									$ (3,762)	$ 1,657	$ 4,032

Derivative Financial Instrume86

Derivative Financial Instruments - Impact of Derivatives on the Statements of Changes in Stockholder's Equity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Amount of loss recognized in other comprehensive income (loss)	$ 8,008	$ (3,901)	$ (26,699)
Amount of loss reclassified in interest expense	(11,187)	(17,665)	(21,475)
Total change in other comprehensive income (loss) for unrealized gains (losses) on derivatives, before income tax (expense) benefit	$ 19,195	$ 13,764	$ (5,224)

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($)	May 05, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 29, 2017
Class of Stock [Line Items]
Common stock, shares authorized (in shares)		1,125,000,000	1,125,000,000
Common stock, par value (in dollars per share)		$ 0.20	$ 0.20
Common stock shares outstanding (in shares)		432,000,000
Common shares unissued but encumbered (in shares)		46,000,000
Common stock dividends		$ 0	$ 0	$ 0
Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock shares outstanding (in shares)	3,300,000	0	3,300,000
Preferred stock dividend rate (as a percentage)		6.97%
Preferred stock dividend rate (in dollars per share)	$ 50
Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock shares outstanding (in shares)		4,000,000	4,000,000
Preferred stock liquidation preference (in dollars per share)		$ 100
Common Stock
Class of Stock [Line Items]
Share price (in dollars per share)					$ 11.30
Three Month LIBOR | Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock dividend rate (as a percentage)		1.70%

Stockholders' Equity - Common S

Stockholders' Equity - Common Stock Repurchased (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity [Abstract]
Shares repurchased related to employee stock-based compensation plans (in shares)	3,358,417	3,354,730	3,008,913
Average purchase price per share (in dollars per share)	$ 11.96	$ 7.83	$ 9.65
Common shares issued (in shares)	6,831,108	5,955,045	5,873,309

Earnings Per Common Share (Deta

Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net income	$ 47,003	$ 76,371	$ 70,617	$ 94,943	$ 70,242	$ 56,965	$ 57,205	$ 65,915	$ 288,934	$ 250,327	$ 274,284
Preferred stock dividends	3,137	3,028	3,974	5,575	5,506	5,316	5,243	5,139	15,714	21,204	19,595
Net income attributable to SLM Corporation common stock	$ 43,866	$ 73,343	$ 66,643	$ 89,368	$ 64,736	$ 51,649	$ 51,962	$ 60,776	$ 273,220	$ 229,123	$ 254,689
Denominator:
Weighted average shares used to compute basic EPS (in shares)									431,216	427,876	425,574
Effect of dilutive securities:
Dilutive effect of stock options, restricted stock, restricted stock units and Employee Stock Purchase Plan (ESPP) (in shares)									7,335	5,043	6,660
Weighted average shares used to compute diluted EPS (in shares)									438,551	432,919	432,234
Basic earnings per common share attributable to SLM Corporation (in dollars per share)	$ 0.10	$ 0.17	$ 0.15	$ 0.21	$ 0.15	$ 0.12	$ 0.12	$ 0.14	$ 0.63	$ 0.54	$ 0.60
Diluted earnings per common share attributable to SLM Corporation (in dollars per share)	$ 0.10	$ 0.17	$ 0.15	$ 0.20	$ 0.15	$ 0.12	$ 0.12	$ 0.14	$ 0.62	$ 0.53	$ 0.59
Antidilutive securities excluded from computation of earnings per share (in shares)									0	1,000	2,000

Stock-Based Compensation Plan90

Stock-Based Compensation Plans and Arrangements - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)compensation_planshares	Dec. 31, 2016USD ($)shares	Dec. 31, 2015USD ($)shares	Jul. 31, 2018USD ($)	Jun. 25, 2014shares	May 24, 2012shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of active stock-based compensation plans | compensation_plan	1
Stock-based compensation cost	$ 27,899,000	$ 22,944,000	$ 21,598,000
Unrecognized compensation cost	$ 14,200,000
Weighted average period for total unrecognized compensation cost	1 year 4 months 15 days
Vesting period	3 years
Options granted in period (in shares) | shares	0	0	0
Offering period of employee stock purchase plan	12 months
Maximum contribution amount per employee to ESPP	$ 7,500
SLM Corporation 2012 Omnibus Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized to be issued under plan (in shares) | shares		23,000,000
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized to be issued under plan (in shares) | shares					15,000,000	6,000,000
Vesting period	1 year
Percentage of discount available to employees under ESPP	15.00%
Expected dividend rate	0.00%	0.00%	0.00%
Company's common stock purchased by ESPP participants (in shares) | shares	283,952	0	163,136
Grants made prior to 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum term for stock options (in years)	10 years
Grants made in 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum term for stock options (in years)	5 years
Performance Vesting Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Performance Vesting Stock Options | Tranche 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage per year of performance-vested options granted to management	33.33%
Performance Vesting Stock Options | Tranche 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage per year of performance-vested options granted to management	33.33%
Performance Vesting Stock Options | Tranche 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage per year of performance-vested options granted to management	33.33%
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 400,000
Weighted average period for total unrecognized compensation cost	6 months
Vesting period	1 year
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Scenario, Forecast | Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost				$ 300,000

Stock-Based Compensation Plan91

Stock-Based Compensation Plans and Arrangements - Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Options
Beginning balance (in shares)	7,595,059
Granted (in shares)	0
Exercised (in shares)	(2,693,347)
Canceled (in shares)	(440,719)
Ending balance (in shares)	4,460,993	7,595,059
Exercisable (in shares)	4,460,993
Weighted Average Exercise Price per Share
Beginning balance (in dollars per share)	$ 10.43
Granted (in dollars per share)	0
Exercised (in dollars per share)	5.80
Canceled (in dollars per share)	15.82
Ending balance (in dollars per share)	11.34	$ 10.43
Exercisable (in dollars per share)	$ 5.38
Weighted Average Remaining Contractual Term
Weighted Average Remaining Contractual Term, Outstanding, ending balance (in years)	1 year 1 month 25 days
Weighted Average Remaining Contractual Term, Exercisable, ending balance (in years)	1 year 1 month 25 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Outstanding, ending balance	$ 26,413
Aggregate Intrinsic Value, Exercisable, ending balance	26,413
Total intrinsic value of options exercised	16,500	$ 9,300	$ 13,700
Cash received from option exercises	100
Tax benefit from exercise of stock options	$ 2,700

Stock-Based Compensation Plan92

Stock-Based Compensation Plans and Arrangements - Restricted Stock and Performance Stock Unit Activity (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Weighted Average Grant Date Fair Value
Unrecognized compensation cost	$ 14.2
Weighted average period for total unrecognized compensation cost	1 year 4 months 15 days
Restricted Stock
Number of Shares
Beginning balance (in shares)	120,879
Granted (in shares)	81,103
Vested and converted to common stock (in shares)	(120,879)
Canceled (in shares)	0
Ending balance (in shares)	81,103	120,879
Weighted Average Grant Date Fair Value
Beginning balance (in dollars per share)	$ 6.37
Granted (in dollars per share)	10.85
Vested (in dollars per share)	6.37
Canceled (in dollars per share)	0
Ending balance (in dollars per share)	$ 10.85	$ 6.37
Fair value of shares vested	$ 0.8	$ 0.8	$ 0.5
Unrecognized compensation cost	$ 0.4
Weighted average period for total unrecognized compensation cost	6 months
Restricted Stock Units And Performance Stock Units
Number of Shares
Beginning balance (in shares)	7,486,610
Granted (in shares)	2,247,337
Vested and converted to common stock (in shares)	(3,765,803)
Canceled (in shares)	(22,854)
Ending balance (in shares)	5,945,290	7,486,610
Weighted Average Grant Date Fair Value
Beginning balance (in dollars per share)	$ 7.21
Granted (in dollars per share)	11.79
Vested (in dollars per share)	7.75
Canceled (in dollars per share)	8.82
Ending balance (in dollars per share)	$ 8.60	$ 7.21
Fair value of restricted stock units that vested and converted to common stock	$ 29.2	$ 22.2	$ 18.9
Unrecognized compensation cost	$ 13.4
Weighted average period for total unrecognized compensation cost	1 year 4 months 24 days

Stock-Based Compensation Plan93

Stock-Based Compensation Plans and Arrangements - Employee Stock Purchase Plan (Details) - Employee Stock Purchase Plan - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Company's common stock purchased by ESPP participants (in shares)	283,952	0	163,136
Risk-free interest rate	1.22%	0.50%	0.33%
Expected volatility	32.00%	32.00%	27.00%
Expected dividend rate	0.00%	0.00%	0.00%
Expected life of the option (in years)	1 year	1 year	1 year
Weighted average fair value of stock purchase rights (in dollars per share)	$ 2.36	$ 1.53	$ 1.74

Fair Value Measurements - Valua

Fair Value Measurements - Valuation of Financial Instruments that are Marked-to-Market on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
Mortgage-backed securities	$ 244,088	$ 208,603
Derivative instruments	0	0
Fair Value Measurements Recurring
Assets
Mortgage-backed securities	244,088	208,603
Derivative instruments	812	7,808
Total	244,900	216,411
Liabilities
Derivative instruments	(2,584)	(25,937)
Fair Value Measurements Recurring | Level 1
Assets
Mortgage-backed securities	0	0
Derivative instruments	0	0
Total	0	0
Liabilities
Derivative instruments	0	0
Fair Value Measurements Recurring | Level 2
Assets
Mortgage-backed securities	244,088	208,603
Derivative instruments	812	7,808
Total	244,900	216,411
Liabilities
Derivative instruments	(2,584)	(25,937)
Fair Value Measurements Recurring | Level 3
Assets
Mortgage-backed securities	0	0
Derivative instruments	0	0
Total	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	Dec. 31, 2017	Dec. 31, 2016
Earning assets
Loans held for investment, net, difference	$ 2,105,495	$ 1,382,864
Tax indemnification receivable	168,011	259,532
Derivative instruments	0	0
Total earning assets, difference	2,105,495	1,382,864
Interest-bearing liabilities
Long-term borrowings, difference	(24,601)	7,874
Total interest-bearing liabilities, difference	(34,688)	(31,565)
Excess of net asset fair value over carrying value	2,070,807	1,351,299
Certificates of Deposit
Interest-bearing liabilities
Certificates of deposits, difference	(10,087)	(39,439)
Fair Value
Earning assets
Loans held for investment, net	20,673,136	16,520,786
Cash and cash equivalents	1,534,339	1,918,793
Available-for-sale investments	244,088	208,603
Accrued interest receivable	967,482	766,106
Tax indemnification receivable	168,011	259,532
Derivative instruments	812	7,808
Total	23,587,868	19,681,628
Interest-bearing liabilities
Short-term borrowings	0	0
Long-term borrowings	3,299,871	2,160,105
Accrued interest payable	35,363	21,058
Derivative instruments	2,584	25,937
Total interest-bearing liabilities	18,852,235	15,681,529
Fair Value | Money-market and savings accounts
Interest-bearing liabilities
Deposits	8,470,209	7,963,925
Fair Value | Certificates of Deposit
Interest-bearing liabilities
Deposits	7,044,208	5,510,504
Carrying Value
Earning assets
Loans held for investment, net	18,567,641	15,137,922
Cash and cash equivalents	1,534,339	1,918,793
Available-for-sale investments	244,088	208,603
Accrued interest receivable	967,482	766,106
Tax indemnification receivable	168,011	259,532
Derivative instruments	812	7,808
Total	21,482,373	18,298,764
Interest-bearing liabilities
Short-term borrowings	0	0
Long-term borrowings	3,275,270	2,167,979
Accrued interest payable	35,363	21,058
Derivative instruments	2,584	25,937
Total interest-bearing liabilities	18,817,547	15,649,964
Carrying Value | Money-market and savings accounts
Interest-bearing liabilities
Deposits	8,470,209	7,963,925
Carrying Value | Certificates of Deposit
Interest-bearing liabilities
Deposits	$ 7,034,121	$ 5,471,065

Arrangements with Navient Cor96

Arrangements with Navient Corporation Arrangements with Navient Corporation (Details) - USD ($)	Apr. 30, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Non-compete period	5 years
Deferred taxes	$ 283,000,000		$ 9,180,000
Remaining amount of indemnification		$ 35,000,000
Remaining balance of indemnification receivable in connection with the spin-off	$ 27,000,000	25,000,000
Deferred tax asset discount		108,000,000
Private education loans		$ 17,432,167,000	14,251,675,000
Minimum days past due for spin off loan purchase		90 days
Period of hardship forbearance		6 months
Private education loans		$ 17,244,830,000	14,113,409,000
Interest income from third party		300,000	300,000	$ 600,000
Gain (loss) resulting from loans sold		0	0	0
Write-down to fair value for loans sold to third party		5,000,000	6,000,000	7,600,000
Split Loans
Related Party Transaction [Line Items]
Private education loans		48,000,000
Participated loans
Related Party Transaction [Line Items]
Loans sold to third party		12,000,000	$ 15,700,000	$ 27,000,000
FFELP Loans
Related Party Transaction [Line Items]
Private education loans		$ 48,000,000
Minimum
Related Party Transaction [Line Items]
Agreements with Navient, period of term (or less)	1 year
Maximum
Related Party Transaction [Line Items]
Agreements with Navient, period of term (or less)	2 years

Regulatory Capital - Well Capit

Regulatory Capital - Well Capitalized Regulatory Requirements (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Actual Amount
Tier 1 Capital (to Average Assets)	$ 2,350,081	$ 2,011,583
Tier 1 Capital (to Risk-Weighted Assets)	2,350,081	2,011,583
Total Capital (to Risk-Weighted Assets)	2,597,926	2,197,997
Tier 1 Capital (to Average Assets)	$ 2,350,081	$ 2,011,583
Actual Ratio
Tier 1 Capital (to Average Assets)	11.90%	12.60%
Tier 1 Capital (to Risk-Weighted Assets)	11.90%	12.60%
Total Capital (to Risk-Weighted Assets)	13.10%	13.80%
Tier 1 Capital (to Average Assets)	11.00%	11.10%
Well Capitalized Regulatory Requirements, Amount
Tier 1 Capital (to Average Assets)	$ 1,288,435	$ 1,038,638
Tier 1 Capital (to Risk-Weighted Assets)	1,585,767	1,278,323
Total Capital (to Risk-Weighted Assets)	1,982,208	1,597,904
Tier 1 Capital (to Average Assets)	$ 1,067,739	$ 907,565
Well Capitalized Regulatory Requirements, Ratio
Tier 1 Capital (to Average 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 ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Sallie Mae Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Dividends	$ 0	$ 0	$ 0

Defined Contribution Plans (Det

Defined Contribution Plans (Details) - Sallie Mae 401(k) Savings Plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan Disclosure [Line Items]
Type 1 of defined benefit contribution (up to)	3.00%
Type 2 of defined contribution plan	2.00%
Percent of core employer contribution	1.00%
Employer contribution amount	$ 5	$ 4.4	$ 3.8
Maximum
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution percentage	100.00%
Minimum
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution percentage	50.00%

Commitments, Contingencies a100

Commitments, Contingencies and Guarantees - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)attorney_generalattorney_general_office
Loss Contingencies [Line Items]
Contractual obligation	$ 1,800
Other liabilities reserve	$ 1.9
Loss emergence period	1 year
Number of state attorneys general | attorney_general_office	2
Washington and Pennsylvania
Loss Contingencies [Line Items]
Number of state attorneys general | attorney_general	2

Income Taxes - Reconciliations

Income Taxes - Reconciliations of Statutory U.S. Federal Income Tax Rates to Our Effective Tax Rate for Continuing Operations (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Statutory rate	35.00%	35.00%	35.00%
Tax reform	3.10%	0.00%	0.00%
State tax, net of federal benefit	2.60%	3.10%	3.00%
Reverse federal impact of indemnification adjustments	2.50%	(0.70%)	0.10%
Unrecognized tax benefits, U.S. federal and state, net of federal benefit	(2.00%)	1.60%	(0.50%)
Excess tax benefits/deficiencies for employee stock-based compensation, federal and state, net of federal benefit	(1.70%)	0.00%	0.00%
Impact of state rate change on net deferred tax liabilities, net of federal benefit	0.60%	(0.50%)	0.50%
State, valuation allowance adjustments on net operating losses	0.20%	1.00%	(0.20%)
Other, net	0.90%	0.10%	(0.40%)
Effective tax rate	41.20%	39.60%	37.50%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Statutory U.S. federal rate	35.00%	35.00%	35.00%
Operating loss carryforwards, valuation allowance	$ 68,600,000	$ 88,400,000
Unrecognized tax benefits	131,608,000	152,581,000	$ 47,109,000	$ 59,405,000
Unrecognized tax benefits recognition impact on effective tax rate	128,200,000
Interest on income taxes accrued net of related benefit	21,200,000	20,200,000	7,000,000
Interest on income tax expense net of related tax benefit	2,700,000	$ 5,100,000	$ 1,400,000
Decrease in Unrecognized Tax Benefits is Reasonably Possible	86.2
State and Local Jurisdiction
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Operating loss carryforwards	$ 5,300,000
Minimum
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Combination of subsidiaries (in years)	3 years
Maximum
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Combination of subsidiaries (in years)	4 years

Income Taxes - Components of Pr

Income Taxes - Components of Provision for Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current provision:
Federal									$ 248,191	$ 228,505	$ 215,950
State									13,092	24,336	26,057
Total current provision									261,283	252,841	242,007
Deferred (benefit)/provision:
Federal									(58,124)	(89,518)	(69,546)
State									(628)	786	(7,681)
Total deferred benefit									(58,752)	(88,732)	(77,227)
Provision for income tax expense	$ 66,190	$ 40,617	$ 44,713	$ 51,011	$ 43,122	$ 47,557	$ 34,555	$ 38,875	$ 202,531	$ 164,109	$ 164,780

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Apr. 30, 2014
Deferred tax assets:
Loan reserves	$ 62,603	$ 72,125
Stock-based compensation plans	10,216	16,471
Deferred revenue	782	793
Operating loss carryovers	4,186	8,371
Unrealized losses	0	5,364
Accrued expenses not currently deductible	5,356	13,605
Unrecorded tax benefits	3,781	5,702
Other	2,410	10,844
Total deferred tax assets	89,334	133,275
Deferred tax liabilities:
Gains on repurchased debt	40,175	126,403
Fixed assets	5,303	6,831
Acquired intangible assets	4,595	6,288
Unrealized gains	1,104	0
Federal deferred for state receivable	3,584	2,058
Other	1,349	875
Total deferred tax liabilities	56,110	142,455
Net deferred tax assets	$ 33,224
Net deferred tax liabilities		$ 9,180	$ 283,000

Income Taxes - Summary of Chang

Income Taxes - Summary of Changes in Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits at beginning of year	$ 152,581	$ 47,109	$ 59,405
Increases resulting from tax positions taken during a prior period	7,482	110,894	3,456
Decreases resulting from tax positions taken during a prior period	(7,025)	(3,285)	(10,121)
Increases resulting from tax positions taken during the current period	1,656	817	3,447
Decreases related to settlements with taxing authorities	(3,594)	(123)	(7,481)
Reductions related to the lapse of statute of limitations	(19,492)	(2,831)	(1,597)
Unrecognized tax benefits at end of year	$ 131,608	$ 152,581	$ 47,109

Parent Only Statements - Balanc

Parent Only Statements - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets
Cash and cash equivalents	$ 1,534,339	$ 1,918,793	$ 2,416,219	$ 2,359,780
Tax indemnification receivable	168,011	259,532
Other assets	84,853	52,153
Total assets	21,779,584	18,533,003
Long-Term	3,275,270	2,167,979
Liabilities
Income taxes payable, net	102,285	184,324
Other liabilities	179,310	141,934
Total liabilities	19,305,328	16,185,945
Preferred stock, par value $0.20 per share, 20 million shares authorized:
Common stock, par value $0.20 per share, 1.125 billion shares authorized: 443.5 million and 436.6 million shares issued, respectively	88,693	87,327
Additional paid-in capital	1,222,277	1,175,564
Accumulated other comprehensive income (loss) (net of tax expense (benefit) of $1,696 and ($5,364), respectively)	2,748	(8,671)
Retained earnings	868,182	595,322
Total SLM Corporation stockholders’ equity before treasury stock	2,581,900	2,414,542
Less: Common stock held in treasury at cost: 11.1 million and 7.7 million shares, respectively	(107,644)	(67,484)
Total equity	2,474,256	2,347,058
Total liabilities and equity	21,779,584	18,533,003
Parent Company
Assets
Cash and cash equivalents	260,255	292,277	$ 282,036	$ 434,245
Total investments in subsidiaries (primarily Sallie Mae Bank)	2,401,114	2,042,015
Tax indemnification receivable	168,011	259,532
Due from subsidiaries, net	37,521	31,834
Other assets	1,279	1,561
Total assets	2,868,180	2,627,219
Long-Term	196,539	0
Liabilities
Income taxes payable, net	159,954	256,556
Payable due to Navient	10,575	2,823
Other liabilities	26,856	20,782
Total liabilities	393,924	280,161
Preferred stock, par value $0.20 per share, 20 million shares authorized:
Common stock, par value $0.20 per share, 1.125 billion shares authorized: 443.5 million and 436.6 million shares issued, respectively	88,693	87,327
Additional paid-in capital	1,222,277	1,175,564
Accumulated other comprehensive income (loss) (net of tax expense (benefit) of $1,696 and ($5,364), respectively)	2,748	(8,671)
Retained earnings	868,182	595,322
Total SLM Corporation stockholders’ equity before treasury stock	2,581,900	2,414,542
Less: Common stock held in treasury at cost: 11.1 million and 7.7 million shares, respectively	(107,644)	(67,484)
Total equity	2,474,256	2,347,058
Total liabilities and equity	2,868,180	2,627,219
Parent Company | Series A Preferred Stock
Preferred stock, par value $0.20 per share, 20 million shares authorized:
Preferred stock issued	0	165,000
Parent Company | Series B Preferred Stock
Preferred stock, par value $0.20 per share, 20 million shares authorized:
Preferred stock issued	$ 400,000	$ 400,000

Parent Only Statements - Bal107

Parent Only Statements - Balance Sheets - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Condensed Financial Statements, Captions [Line Items]
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)	443,500,000	436,600,000
Accumulated other comprehensive loss tax benefit	$ 1,696	$ (5,364)
Common stock held in treasury (in shares)	11,100,000	7,700,000
Series A Preferred Stock
Condensed Financial Statements, Captions [Line Items]
Preferred stock, stated value (in dollars per share)	$ 50	$ 50
Series B Preferred Stock
Condensed Financial Statements, Captions [Line Items]
Preferred stock, stated value (in dollars per share)	100	100
Parent Company
Condensed Financial Statements, Captions [Line Items]
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)	443,500,000	436,600,000
Accumulated other comprehensive loss tax benefit	$ 1,696	$ (5,364)
Common stock held in treasury (in shares)	11,100,000	7,700,000
Parent Company | Series A Preferred Stock
Condensed Financial Statements, Captions [Line Items]
Preferred stock, stated value (in dollars per share)	$ 0	$ 50
Preferred stock, shares issued (in shares)	0	3,300,000
Parent Company | Series B Preferred Stock
Condensed Financial Statements, Captions [Line Items]
Preferred stock, stated value (in dollars per share)	$ 100	$ 100
Preferred stock, shares issued (in shares)	4,000,000	4,000,000

Parent Only Statements - Statem

Parent Only Statements - Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Income Statements, Captions [Line Items]
Interest income									$ 1,437,303	$ 1,077,246	$ 831,118
Interest expense									308,082	185,908	128,619
Net interest income	$ 309,191	$ 282,061	$ 269,893	$ 268,076	$ 245,434	$ 223,275	$ 212,766	$ 209,863	1,129,221	891,338	702,499
Non-interest income (loss)									(2,902)	68,816	182,593
Non-interest expenses									449,089	386,313	355,973
Income tax benefit	66,190	40,617	44,713	51,011	43,122	47,557	34,555	38,875	202,531	164,109	164,780
Net income									288,934	250,327	274,284
Preferred stock dividends	3,137	3,028	3,974	5,575	5,506	5,316	5,243	5,139	15,714	21,204	19,595
Net income attributable to SLM Corporation common stock	$ 43,866	$ 73,343	$ 66,643	$ 89,368	$ 64,736	$ 51,649	$ 51,962	$ 60,776	273,220	229,123	254,689
Parent Company
Condensed Income Statements, Captions [Line Items]
Interest income									5,497	5,367	6,414
Interest expense									8,170	0	0
Net interest income									(2,673)	5,367	6,414
Non-interest income (loss)									(33,956)	9,396	(239)
Non-interest expenses									35,810	32,553	36,141
Loss before income tax benefit and equity in net income from subsidiaries									(72,439)	(17,790)	(29,966)
Income tax benefit									(40,598)	(2,839)	(8,612)
Equity in net income from subsidiaries (primarily Sallie Mae Bank)									320,775	265,278	295,638
Net income									288,934	250,327	274,284
Preferred stock dividends									15,714	21,204	19,595
Net income attributable to SLM Corporation common stock									$ 273,220	$ 229,123	$ 254,689

Parent Only Statements - Sta109

Parent Only Statements - Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 288,934	$ 250,327	$ 274,284
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Loss (income) on tax indemnification receivable	31,888	(12,283)	(5,398)
Amortization of unsecured debt upfront fees	1,316	1,229	2,337
Decrease in tax indemnification receivable	59,633	59,633	59,633
Increase in other assets	(72,920)	(47,162)	(18,070)
Decrease in income taxes payable, net	(19,687)	(20,647)	62,953
(Decrease) increase in payable due to entity that is a subsidiary of Navient	(593)	553	(6,774)
Increase in other liabilities	2,171	14,562	(14,731)
Total adjustments	(455,846)	(452,909)	(359,347)
Total net cash used in operating activities	(166,912)	(202,582)	(85,063)
Cash flows from investing activities:
Net cash provided by (used in) investing activities	(3,212,516)	(3,331,041)	(1,847,509)
Cash flows from financing activities:
Unsecured debt issued	197,000	0	0
Issuance costs for unsecured debt offering	(1,057)	0	0
Redemption of Series A Preferred Stock	(165,000)	0	0
Preferred stock dividends paid	(15,714)	(21,204)	(19,595)
Net cash provided by (used in) financing activities	2,994,974	3,036,197	1,989,011
Net (decrease) increase in cash and cash equivalents	(384,454)	(497,426)	56,439
Cash and cash equivalents at beginning of year	1,918,793	2,416,219	2,359,780
Cash and cash equivalents at end of year	1,534,339	1,918,793	2,416,219
Parent Company
Cash flows from operating activities:
Net income	288,934	250,327	274,284
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Undistributed earnings of subsidiaries	(320,775)	(265,278)	(295,638)
Loss (income) on tax indemnification receivable	31,888	(12,283)	(5,398)
Amortization of unsecured debt upfront fees	596	0	0
Decrease (increase) in investment in subsidiaries, net	1,158	63,222	(103,602)
Decrease in tax indemnification receivable	59,633	59,633	59,633
(Increase) decrease in due from subsidiaries, net	(5,687)	(10,438)	11,012
Increase in other assets	(24,627)	(8,972)	(14,366)
Decrease in income taxes payable, net	(87,983)	(54,175)	(53,167)
(Decrease) increase in payable due to entity that is a subsidiary of Navient	(593)	553	(6,774)
Increase in other liabilities	10,205	8,856	1,402
Total adjustments	(336,185)	(218,882)	(406,898)
Total net cash used in operating activities	(47,251)	31,445	(132,614)
Cash flows from investing activities:
Net cash provided by (used in) investing activities	0	0	0
Cash flows from financing activities:
Unsecured debt issued	197,000	0	0
Issuance costs for unsecured debt offering	(1,057)	0	0
Redemption of Series A Preferred Stock	(165,000)	0	0
Preferred stock dividends paid	(15,714)	(21,204)	(19,595)
Net cash provided by (used in) financing activities	15,229	(21,204)	(19,595)
Net (decrease) increase in cash and cash equivalents	(32,022)	10,241	(152,209)
Cash and cash equivalents at beginning of year	292,277	282,036	434,245
Cash and cash equivalents at end of year	$ 260,255	$ 292,277	$ 282,036

Selected Quarterly Financial110

Selected Quarterly Financial Information (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Net interest income	$ 309,191	$ 282,061	$ 269,893	$ 268,076	$ 245,434	$ 223,275	$ 212,766	$ 209,863	$ 1,129,221	$ 891,338	$ 702,499
Less: provisions for credit losses	55,324	54,930	50,215	25,296	43,226	41,784	41,793	32,602	185,765	159,405	90,055
Net interest income after provisions for credit losses	253,867	227,131	219,678	242,780	202,208	181,491	170,973	177,261	943,456	731,933	612,444
Gains on sales of loans, net					230	0	0	0
(Losses) gains on derivative and hedging activities, net	(940)	1,661	(3,609)	(5,378)	(4,114)	1,368	2,142	(354)
Other income (loss)	(21,066)	4,455	10,629	11,346	13,235	21,598	13,683	21,028	5,364	69,544	41,935
Total operating expenses	118,550	116,142	111,251	102,677	98,036	99,709	94,777	92,885	448,620	385,407	349,095
Acquired intangible asset amortization expense	118	117	117	117	159	226	261	260
Restructuring and other reorganization expenses									0	0	5,398
Income tax benefit	66,190	40,617	44,713	51,011	43,122	47,557	34,555	38,875	202,531	164,109	164,780
Net income	47,003	76,371	70,617	94,943	70,242	56,965	57,205	65,915	288,934	250,327	274,284
Preferred stock dividends	3,137	3,028	3,974	5,575	5,506	5,316	5,243	5,139	15,714	21,204	19,595
Net income attributable to SLM Corporation common stock	$ 43,866	$ 73,343	$ 66,643	$ 89,368	$ 64,736	$ 51,649	$ 51,962	$ 60,776	$ 273,220	$ 229,123	$ 254,689
Basic earnings per common share attributable to SLM Corporation (in dollars per share)	$ 0.10	$ 0.17	$ 0.15	$ 0.21	$ 0.15	$ 0.12	$ 0.12	$ 0.14	$ 0.63	$ 0.54	$ 0.60
Diluted earnings per common share attributable to SLM Corporation (in dollars per share)	$ 0.10	$ 0.17	$ 0.15	$ 0.20	$ 0.15	$ 0.12	$ 0.12	$ 0.14	$ 0.62	$ 0.53	$ 0.59

Subsequent Events (Details)

Subsequent Events (Details) - Commercial Paper - ABCP borrowings - USD ($)	Feb. 21, 2018	Feb. 22, 2017
Subsequent Event [Line Items]
Private education loan funding		$ 750,000,000
Subsequent Event
Subsequent Event [Line Items]
Private education loan funding	$ 750,000,000
Minimum
Subsequent Event [Line Items]
Unused borrowing capacity fee (as a percent)		0.35%
Minimum | Subsequent Event
Subsequent Event [Line Items]
Unused borrowing capacity fee (as a percent)	0.35%
Maximum
Subsequent Event [Line Items]
Unused borrowing capacity fee (as a percent)		0.45%
Maximum | Subsequent Event
Subsequent Event [Line Items]
Unused borrowing capacity fee (as a percent)	0.45%
London Interbank Offered Rate (LIBOR)
Subsequent Event [Line Items]
Basis spread on variable rate		0.85%
London Interbank Offered Rate (LIBOR) | Subsequent Event
Subsequent Event [Line Items]
Basis spread on variable rate	0.85%