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Allowance for Loan Losses - Allowance for Credit Losses and Recorded Investments in Loans (Detail) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2017 USD ($) SecurityLoan | Mar. 31, 2016 USD ($) SecurityLoan
Allowance for Loan Losses |  |
Beginning balance | $ 1,433 | $ 1,564
Provision for loan losses | 107 | 111
Charge-offs | (151) | (160)
Reclassification of interest reserve | 2 | 3
Ending balance | 1,391 | 1,518
Allowance: |  |
Ending balance: individually evaluated for impairment | 1,186 | 1,196
Ending balance: collectively evaluated for impairment | 205 | 322
Loans: |  |
Ending balance: individually evaluated for impairment | 11,127 | 11,121
Ending balance: collectively evaluated for impairment | 97,866 | 110,435
FFELP Loans [Member] |  |
Allowance for Loan Losses |  |
Beginning balance | 67 | 78
Provision for loan losses | 10 | 7
Charge-offs | (13) | (16)
Ending balance | 64 | 69
Allowance: |  |
Ending balance: collectively evaluated for impairment | 64 | 69
Loans: |  |
Ending balance: collectively evaluated for impairment | $ 84,513 | $ 93,977
Charge-offs as a percentage of average loans in repayment (annualized) | 0.07% | 0.09%
Allowance coverage of charge-offs (annualized) | SecurityLoan | 1.2 | 1.1
Allowance as a percentage of the ending total loan balance | 0.08% | 0.07%
Allowance as a percentage of the ending loans in repayment | 0.09% | 0.09%
Ending total loans | $ 84,513 | $ 93,977
Average loans in repayment | 69,302 | 73,697
Ending loans in repayment | 68,095 | 73,630
Private Education Loans [Member] |  |
Allowance for Loan Losses |  |
Beginning balance | 1,351 | 1,471
Provision for loan losses | 95 | 104
Charge-offs | (137) | (144)
Reclassification of interest reserve | 2 | 3
Ending balance | 1,311 | 1,434
Allowance: |  |
Ending balance: individually evaluated for impairment | 1,176 | 1,185
Ending balance: collectively evaluated for impairment | 135 | 249
Loans: |  |
Ending balance: individually evaluated for impairment | 11,096 | 11,088
Ending balance: collectively evaluated for impairment | $ 13,201 | $ 16,408
Charge-offs as a percentage of average loans in repayment (annualized) | 2.56% | 2.39%
Allowance coverage of charge-offs (annualized) | SecurityLoan | 2.4 | 2.5
Allowance as a percentage of the ending total loan balance | 5.39% | 5.22%
Allowance as a percentage of the ending loans in repayment | 6.13% | 6.03%
Ending total loans | $ 24,297 | $ 27,496
Average loans in repayment | 21,791 | 24,180
Ending loans in repayment | 21,367 | 23,786
Other Loans [Member] |  |
Allowance for Loan Losses |  |
Beginning balance | 15 | 15
Provision for loan losses | 2 |
Charge-offs | (1) |
Ending balance | 16 | 15
Allowance: |  |
Ending balance: individually evaluated for impairment | 10 | 11
Ending balance: collectively evaluated for impairment | 6 | 4
Loans: |  |
Ending balance: individually evaluated for impairment | 31 | 33
Ending balance: collectively evaluated for impairment | $ 152 | $ 50
Charge-offs as a percentage of average loans in repayment (annualized) | 2.06% | 2.04%
Allowance coverage of charge-offs (annualized) | SecurityLoan | 4.6 | 8.6
Allowance as a percentage of the ending total loan balance | 9.00% | 17.91%
Allowance as a percentage of the ending loans in repayment | 9.00% | 17.91%
Ending total loans | $ 183 | $ 83
Average loans in repayment | 173 | 85
Ending loans in repayment | $ 183 | $ 83

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- Definition Allowance as a percentage of ending loans in repayment. + References No definition available. + Details
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- Definition Net charge offs as percentage of average loans in repayment. + References No definition available. + Details
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- Definition Amount of other addition (reduction) in allowance reserve for credit loss. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5212-111524 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.7(d)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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- Definition The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524 + Details
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- Definition Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524 + Details
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- Definition Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.7(d)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section S99 -Paragraph 4 -Subparagraph (SAB Topic 6.L.1) -URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (b)(1)(ii) -URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544 + Details
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