XML 55 R45.htm IDEA: XBRL DOCUMENT v3.8.0.1
Allowance for Loan Losses - Age Analysis of Past Due Loans Delinquencies (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Loans in repayment and percentage of each status:        
Loans allowance for losses $ (1,367) $ (1,433) $ (1,564) $ (2,033)
Loans, net 105,122 111,070    
FFELP Loans [Member]        
Loans in repayment and percentage of each status:        
Total loans in repayment 67,853 70,557 73,838  
Loans allowance for losses (60) (67) (78) $ (93)
Loans, net 81,703 87,730    
Credit Concentration Risk [Member] | Private Education Loans - TDR [Member]        
Financing Receivable Recorded Investment Past Due [Line Items]        
Total loans, gross 10,536 10,805 10,642  
Loans in repayment and percentage of each status:        
Loans current 8,333 8,273 7,887  
Total loans in repayment 9,378 9,638 9,242  
Total loans, gross 10,536 10,805 10,642  
Loans unamortized premium (discount) (225) (237) (243)  
Total loans 10,311 10,568 10,399  
Loans allowance for losses (1,171) (1,190) (1,209)  
Loans, net 9,525 9,738 9,513  
Loans receivable for partially charged-off loans 385 360 323  
Credit Concentration Risk [Member] | Private Education Loans - Non-TDR [Member]        
Financing Receivable Recorded Investment Past Due [Line Items]        
Total loans, gross 14,344 13,528 16,873  
Loans in repayment and percentage of each status:        
Total loans in repayment 13,546 12,512 15,260  
Total loans, gross 14,344 13,528 16,873  
Loans unamortized premium (discount) (699) (220) (288)  
Total loans 13,645 13,308 16,585  
Loans allowance for losses (126) (161) (262)  
Loans, net 13,894 13,602 16,881  
Loans receivable for partially charged-off loans $ 375 $ 455 $ 558  
Credit Concentration Risk [Member] | Accounts Receivable [Member] | Private Education Loans - TDR [Member]        
Loans in repayment and percentage of each status:        
Dimensions of concentration risk 100.00% 100.00% 100.00%  
Credit Concentration Risk [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDR [Member]        
Loans in repayment and percentage of each status:        
Dimensions of concentration risk 100.00% 100.00% 100.00%  
Credit Concentration Risk [Member] | Financing Receivables, 31 to 60 Days Past Due [Member] | Private Education Loans - TDR [Member]        
Loans in repayment and percentage of each status:        
Loans delinquent $ 351 $ 412 $ 414  
Credit Concentration Risk [Member] | Financing Receivables, 31 to 60 Days Past Due [Member] | Private Education Loans - Non-TDR [Member]        
Loans in repayment and percentage of each status:        
Loans delinquent $ 120 $ 110 $ 163  
Credit Concentration Risk [Member] | Financing Receivables, 31 to 60 Days Past Due [Member] | Accounts Receivable [Member] | Private Education Loans - TDR [Member]        
Loans in repayment and percentage of each status:        
Loans delinquent, percentage 3.70% 4.30% 4.50%  
Credit Concentration Risk [Member] | Financing Receivables, 31 to 60 Days Past Due [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDR [Member]        
Loans in repayment and percentage of each status:        
Loans delinquent, percentage 0.90% 0.90% 1.10%  
Credit Concentration Risk [Member] | Financing Receivables, 61 to 90 Days Past Due [Member] | Private Education Loans - TDR [Member]        
Loans in repayment and percentage of each status:        
Loans delinquent $ 207 $ 267 $ 263  
Credit Concentration Risk [Member] | Financing Receivables, 61 to 90 Days Past Due [Member] | Private Education Loans - Non-TDR [Member]        
Loans in repayment and percentage of each status:        
Loans delinquent $ 59 $ 54 $ 85  
Credit Concentration Risk [Member] | Financing Receivables, 61 to 90 Days Past Due [Member] | Accounts Receivable [Member] | Private Education Loans - TDR [Member]        
Loans in repayment and percentage of each status:        
Loans delinquent, percentage 2.20% 2.80% 2.90%  
Credit Concentration Risk [Member] | Financing Receivables, 61 to 90 Days Past Due [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDR [Member]        
Loans in repayment and percentage of each status:        
Loans delinquent, percentage 0.40% 0.40% 0.60%  
Credit Concentration Risk [Member] | Financing Receivables, 90 Days Past Due [Member] | Private Education Loans - TDR [Member]        
Loans in repayment and percentage of each status:        
Loans delinquent $ 487 $ 686 $ 678  
Credit Concentration Risk [Member] | Financing Receivables, 90 Days Past Due [Member] | Private Education Loans - Non-TDR [Member]        
Loans in repayment and percentage of each status:        
Loans delinquent $ 110 $ 115 $ 168  
Credit Concentration Risk [Member] | Financing Receivables, 90 Days Past Due [Member] | Accounts Receivable [Member] | Private Education Loans - TDR [Member]        
Loans in repayment and percentage of each status:        
Loans delinquent, percentage 5.20% 7.10% 7.30%  
Credit Concentration Risk [Member] | Financing Receivables, 90 Days Past Due [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDR [Member]        
Loans in repayment and percentage of each status:        
Loans delinquent, percentage 0.80% 0.90% 1.00%  
Credit Concentration Risk [Member] | Financing Receivables, Current [Member] | Private Education Loans - Non-TDR [Member]        
Loans in repayment and percentage of each status:        
Loans current $ 13,257 $ 12,233 $ 14,844  
Credit Concentration Risk [Member] | Financing Receivables, Current [Member] | Accounts Receivable [Member] | Private Education Loans - TDR [Member]        
Loans in repayment and percentage of each status:        
Dimensions of concentration risk 88.90% 85.80% 85.30%  
Credit Concentration Risk [Member] | Financing Receivables, Current [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDR [Member]        
Loans in repayment and percentage of each status:        
Dimensions of concentration risk 97.90% 97.80% 97.30%  
Credit Concentration Risk [Member] | Financing Receivables, Loans In Repayment [Member] | Accounts Receivable [Member] | Private Education Loans - TDR [Member]        
Loans in repayment and percentage of each status:        
Dimensions of concentration risk 89.00% 89.20% 86.80%  
Credit Concentration Risk [Member] | Financing Receivables, Loans In Repayment [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDR [Member]        
Loans in repayment and percentage of each status:        
Dimensions of concentration risk 94.40% 92.50% 90.40%  
Credit Concentration Risk [Member] | Financing Receivables, Delinquent Loans in Repayment [Member] | Accounts Receivable [Member] | Private Education Loans - TDR [Member]        
Loans in repayment and percentage of each status:        
Dimensions of concentration risk 11.10% 14.20% 14.70%  
Credit Concentration Risk [Member] | Financing Receivables, Delinquent Loans in Repayment [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDR [Member]        
Loans in repayment and percentage of each status:        
Dimensions of concentration risk 2.10% 2.20% 2.70%  
Credit Concentration Risk [Member] | Financing Receivables, Forbearance, Loans In Repayment [Member] | Accounts Receivable [Member] | Private Education Loans - TDR [Member]        
Loans in repayment and percentage of each status:        
Dimensions of concentration risk 6.80% 5.70% 7.00%  
Credit Concentration Risk [Member] | Financing Receivables, Forbearance, Loans In Repayment [Member] | Accounts Receivable [Member] | Private Education Loans - Non-TDR [Member]        
Loans in repayment and percentage of each status:        
Dimensions of concentration risk 1.60% 1.60% 1.80%  
Credit Concentration Risk [Member] | School/Grace/Deferment [Member] | Private Education Loans - TDR [Member]        
Financing Receivable Recorded Investment Past Due [Line Items]        
Total loans, gross $ 477 $ 579 $ 706  
Loans in repayment and percentage of each status:        
Total loans, gross 477 579 706  
Credit Concentration Risk [Member] | School/Grace/Deferment [Member] | Private Education Loans - Non-TDR [Member]        
Financing Receivable Recorded Investment Past Due [Line Items]        
Total loans, gross 584 814 1,334  
Loans in repayment and percentage of each status:        
Total loans, gross 584 814 1,334  
Credit Concentration Risk [Member] | Forbearance [Member] | Private Education Loans - TDR [Member]        
Financing Receivable Recorded Investment Past Due [Line Items]        
Total loans, gross 681 588 694  
Loans in repayment and percentage of each status:        
Total loans, gross 681 588 694  
Credit Concentration Risk [Member] | Forbearance [Member] | Private Education Loans - Non-TDR [Member]        
Financing Receivable Recorded Investment Past Due [Line Items]        
Total loans, gross 214 202 279  
Loans in repayment and percentage of each status:        
Total loans, gross 214 202 279  
Credit Concentration Risk [Member] | FFELP Loans [Member]        
Financing Receivable Recorded Investment Past Due [Line Items]        
Total loans, gross 81,097 86,918 95,393  
Loans in repayment and percentage of each status:        
Loans current 59,264 61,977 62,651  
Total loans in repayment 67,853 70,557 73,838  
Total loans, gross 81,097 86,918 95,393  
Loans unamortized premium (discount) 666 879 1,087  
Total loans 81,763 87,797 96,480  
Loans allowance for losses (60) (67) (78)  
Loans, net $ 81,703 $ 87,730 $ 96,402  
Credit Concentration Risk [Member] | FFELP Loans [Member] | Accounts Receivable [Member]        
Loans in repayment and percentage of each status:        
Dimensions of concentration risk 100.00% 100.00% 100.00%  
Credit Concentration Risk [Member] | FFELP Loans [Member] | Financing Receivables, 31 to 60 Days Past Due [Member]        
Loans in repayment and percentage of each status:        
Loans delinquent $ 2,638 $ 2,820 $ 3,285  
Credit Concentration Risk [Member] | FFELP Loans [Member] | Financing Receivables, 31 to 60 Days Past Due [Member] | Accounts Receivable [Member]        
Loans in repayment and percentage of each status:        
Loans delinquent, percentage 3.90% 4.00% 4.50%  
Credit Concentration Risk [Member] | FFELP Loans [Member] | Financing Receivables, 61 to 90 Days Past Due [Member]        
Loans in repayment and percentage of each status:        
Loans delinquent $ 1,763 $ 1,325 $ 1,856  
Credit Concentration Risk [Member] | FFELP Loans [Member] | Financing Receivables, 61 to 90 Days Past Due [Member] | Accounts Receivable [Member]        
Loans in repayment and percentage of each status:        
Loans delinquent, percentage 2.60% 1.90% 2.50%  
Credit Concentration Risk [Member] | FFELP Loans [Member] | Financing Receivables, 90 Days Past Due [Member]        
Loans in repayment and percentage of each status:        
Loans delinquent $ 4,188 $ 4,435 $ 6,046  
Credit Concentration Risk [Member] | FFELP Loans [Member] | Financing Receivables, 90 Days Past Due [Member] | Accounts Receivable [Member]        
Loans in repayment and percentage of each status:        
Loans delinquent, percentage 6.20% 6.30% 8.20%  
Credit Concentration Risk [Member] | FFELP Loans [Member] | Financing Receivables, Current [Member] | Accounts Receivable [Member]        
Loans in repayment and percentage of each status:        
Dimensions of concentration risk 87.30% 87.80% 84.80%  
Credit Concentration Risk [Member] | FFELP Loans [Member] | Financing Receivables, Loans In Repayment [Member] | Accounts Receivable [Member]        
Loans in repayment and percentage of each status:        
Dimensions of concentration risk 83.70% 81.20% 77.40%  
Credit Concentration Risk [Member] | FFELP Loans [Member] | Financing Receivables, Delinquent Loans in Repayment [Member] | Accounts Receivable [Member]        
Loans in repayment and percentage of each status:        
Dimensions of concentration risk 12.70% 12.20% 15.20%  
Credit Concentration Risk [Member] | FFELP Loans [Member] | Financing Receivables, Forbearance, Loans In Repayment [Member] | Accounts Receivable [Member]        
Loans in repayment and percentage of each status:        
Dimensions of concentration risk 11.20% 12.90% 15.30%  
Credit Concentration Risk [Member] | FFELP Loans [Member] | School/Grace/Deferment [Member]        
Financing Receivable Recorded Investment Past Due [Line Items]        
Total loans, gross $ 4,711 $ 5,871 $ 8,257  
Loans in repayment and percentage of each status:        
Total loans, gross 4,711 5,871 8,257  
Credit Concentration Risk [Member] | FFELP Loans [Member] | Forbearance [Member]        
Financing Receivable Recorded Investment Past Due [Line Items]        
Total loans, gross 8,533 10,490 13,298  
Loans in repayment and percentage of each status:        
Total loans, gross $ 8,533 $ 10,490 $ 13,298