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Borrowings - Company's Borrowings (Parenthetical) (Detail) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2017 | Dec. 31, 2016
Debt Instrument [Line Items] |  |
Long-term debt | $ 109,586 | $ 112,368
Short-term Debt | 2,160 | 2,334
Total Before Hedge Accounting Adjustments [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | 110,223 | 113,119
Short-term Debt | 2,161 | 2,335
Other [Member] | Total Before Hedge Accounting Adjustments [Member] |  |
Debt Instrument [Line Items] |  |
Short-term Debt | 502 | 606
Private Education Loan Securitizations Repurchase Facility [Member] | Total Before Hedge Accounting Adjustments [Member] |  |
Debt Instrument [Line Items] |  |
Long-term debt | 476 | 475
Short-term Debt | 548 | 548
Maturity Overnight [Member] | Other [Member] | Total Before Hedge Accounting Adjustments [Member] |  |
Debt Instrument [Line Items] |  |
Securities re-pledged subject to an overnight repurchase transaction | $ 95 | $ 193

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- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 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(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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