XML 132 R56.htm IDEA: XBRL DOCUMENT
v3.19.3.a.u2

Loans Held for Investment - Student Loan Portfolio Average Balances (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Receivables [Abstract] |  |  |
Average balance of Private Education Loans | $ 22,225,473 | $ 19,282,500 | $ 16,176,351
Average Balance, FFELP Loans | 814,198 | 888,301 | 970,738
Average Balance of Personal Loans | 1,141,503 | 900,152 | 112,644
Average Balance, Total portfolio | $ 24,181,174 | $ 21,070,953 | $ 17,259,733
Weighted Average Interest Rate, Private Education Loans | 9.32% | 9.10% | 8.43%
Weighted Average Interest Rate, FFELP Loans | 4.79% | 4.57% | 3.91%
Weighted Average Interest Rate of Personal Loans | 12.09% | 11.08% | 9.90%

X
- Definition Average Balance Ffelp Loans + References No definition available. + Details
Name: | slm_AverageBalanceFfelpLoans
Namespace Prefix: | slm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Average Balance of Personal Loans + References No definition available. + Details
Name: | slm_AverageBalanceofPersonalLoans
Namespace Prefix: | slm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Average balance of Private Education Loans + References No definition available. + Details
Name: | slm_AveragebalanceofPrivateEducationLoans
Namespace Prefix: | slm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Loans and Lease Receivable, Net, Average Balance + References No definition available. + Details
Name: | slm_LoansandLeaseReceivableNetAverageBalance
Namespace Prefix: | slm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- References No definition available. + Details
Name: | slm_WeightedAverageInterestRateFfelploans
Namespace Prefix: | slm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted Average Interest Rate of Personal Loans + References No definition available. + Details
Name: | slm_WeightedAverageInterestRateofPersonalLoans
Namespace Prefix: | slm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | slm_WeightedAverageInterestRateofPrivateEducationLoans
Namespace Prefix: | slm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_ReceivablesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration