Estimated weighted average life of student loans.

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- Definition

Lendable value of collateral

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- Definition

Loans Pledged As Collateral, Capitalized Interest

+ References

No definition available.

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- Definition

Loans Pledged As Collateral, Principal Amount

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No definition available.

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- Definition

Loans Securitized or Asset-Backed Financing Arrangement, Ownership Interest, Percentage

+ References

No definition available.

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- Definition

Ownership Interest Percentage

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No definition available.

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- Definition

Uncommitted Federal Funds

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No definition available.

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- Definition

Principal amount of transferred financial assets in which the transferor has continuing involvement with the assets underlying the transaction. Continuing involvement includes, but is not limited to, servicing, recourse, and restrictions on transferor's interests in transferred financial assets.

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-Publisher FASB
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-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4
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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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- Definition

Face (par) amount of debt instrument at time of issuance.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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- Definition

Carrying amount as of the balance sheet date of loans that have been pledged as collateral for borrowings. If the secured party has the right by contract or custom to sell or re-pledge the collateral, then the debtor reclassifies that asset and report that asset in its statement of financial position separately from other assets not so encumbered.

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- Definition

This is the principal amount outstanding for loans which are in the process of being securitized as of the date of the statement of financial position (across all types of loans).

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- Definition

The cash inflow from the issuance of long-term debt that is not secured by collateral. Excludes proceeds from tax exempt unsecured debt.

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- Definition

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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Borrowings - Additional Information (Details) - USD ($)				9 Months Ended	12 Months Ended
Borrowings - Additional Information (Details) - USD ($)	Jun. 12, 2019	Mar. 13, 2019	Feb. 20, 2019	Sep. 30, 2019	Dec. 31, 2018	Dec. 31, 2017	Apr. 05, 2017
Line of Credit Facility [Line Items]
Short-term borrowings				$ 297,800,000	$ 0
Unsecured offering issued				$ 1,110,000,000	$ 1,900,500,000	$ 1,448,000,000
Estimated weighted average life of student loans				5 years 4 months 24 days	5 years 4 months 24 days
Uncommitted federal funds				$ 125,000,000
Lendable value of collateral				3,200,000,000	$ 3,100,000,000
Unsecured borrowings
Line of Credit Facility [Line Items]
Short-term borrowings				0	0
Senior Unsecured Notes Due April 5, 2022 \| Unsecured borrowings
Line of Credit Facility [Line Items]
Unsecured offering issued				198,000,000			$ 200,000,000
Interest rate stated percentage							5.125%
Private Education Loans 2019 Term A
Line of Credit Facility [Line Items]
Total loan amount securitized at inception		$ 453,000,000
Amount of loan securitization sold to third parties		$ 453,000,000
Ownership interest percentage		100.00%
Proceeds from loan securitization sold to third parties		$ 451,000,000
Loans pledged as collateral				464,000,000
Principal amount of collateral				430,000,000
Capitalized interest				34,000,000
Class A and B Notes
Line of Credit Facility [Line Items]
Estimated weighted average life of student loans	4 years 4 months 28 days	4 years 3 months 3 days
Class A and B Notes \| London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.01%	0.92%
Private Education Loans 2019 Term B
Line of Credit Facility [Line Items]
Total loan amount securitized at inception	$ 657,000,000
Amount of loan securitization sold to third parties	$ 657,000,000
Ownership interest percentage	100.00%
Proceeds from loan securitization sold to third parties	$ 655,000,000
Loans pledged as collateral				688,000,000
Principal amount of collateral				641,000,000
Capitalized interest				47,000,000
Commercial Paper \| ABCP borrowings
Line of Credit Facility [Line Items]
Private asset backed commercial paper education loan funding facility			$ 750,000,000
Ownership interest percentage in residual interest in ABCP facility			100.00%
Short-term borrowings				$ 298,000,000	$ 0