Borrowings - Financing VIEs (Detail) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Securities Financing Transaction [Line Items]
Short-term borrowings	$ 2,370	$ 2,570
Long-term borrowings	119,637	124,833
Total Debt Outstanding	122,007	127,403
Other assets	4,782	4,682
Total Before Hedge Accounting Adjustments [Member]
Securities Financing Transaction [Line Items]
Short-term borrowings	2,393	2,590
Long-term borrowings	119,276	124,916
Total Debt Outstanding	121,669	127,506
Hedge Accounting Adjustments [Member]
Securities Financing Transaction [Line Items]
Short-term borrowings	(23)	(20)
Long-term borrowings	361	(83)
Total Debt Outstanding	338	(103)
Assets and Liabilities of Consolidated Variable Interest Entities [Member]
Securities Financing Transaction [Line Items]
Short-term borrowings	361	710
Long-term borrowings	102,103	106,510
Total Debt Outstanding	102,464	107,220
Loans	109,360	114,640
Cash	3,419	3,553
Other assets	432	293
Total Carrying Amount of Assets Securing Debt Outstanding	113,211	118,486
Assets and Liabilities of Consolidated Variable Interest Entities [Member] \| FFELP Loan Securitizations [Member]
Securities Financing Transaction [Line Items]
Long-term borrowings	75,698	77,764
Total Debt Outstanding	75,698	77,764
Loans	76,330	78,358
Cash	2,649	2,760
Other assets	754	682
Total Carrying Amount of Assets Securing Debt Outstanding	79,733	81,800
Assets and Liabilities of Consolidated Variable Interest Entities [Member] \| Private Education Loan Securitizations [Member]
Securities Financing Transaction [Line Items]
Long-term borrowings	16,168	16,900
Total Debt Outstanding	16,168	16,900
Loans	21,213	22,014
Cash	477	452
Other assets	284	323
Total Carrying Amount of Assets Securing Debt Outstanding	21,974	22,789
Assets and Liabilities of Consolidated Variable Interest Entities [Member] \| FFELP Loan - Other Facilities [Member]
Securities Financing Transaction [Line Items]
Long-term borrowings	11,009	12,676
Total Debt Outstanding	11,009	12,676
Loans	11,283	13,158
Cash	285	324
Other assets	171	168
Total Carrying Amount of Assets Securing Debt Outstanding	11,739	13,650
Assets and Liabilities of Consolidated Variable Interest Entities [Member] \| Private Education Loan - Other Facilities [Member]
Securities Financing Transaction [Line Items]
Short-term borrowings	361	710
Total Debt Outstanding	361	710
Loans	534	1,110
Cash	8	17
Other assets	16	31
Total Carrying Amount of Assets Securing Debt Outstanding	558	1,158
Assets and Liabilities of Consolidated Variable Interest Entities [Member] \| Total Before Hedge Accounting Adjustments [Member]
Securities Financing Transaction [Line Items]
Short-term borrowings	361	710
Long-term borrowings	102,875	107,340
Total Debt Outstanding	103,236	108,050
Loans	109,360	114,640
Cash	3,419	3,553
Other assets	1,225	1,204
Total Carrying Amount of Assets Securing Debt Outstanding	114,004	119,397
Assets and Liabilities of Consolidated Variable Interest Entities [Member] \| Hedge Accounting Adjustments [Member]
Securities Financing Transaction [Line Items]
Long-term borrowings	(772)	(830)
Total Debt Outstanding	(772)	(830)
Other assets	(793)	(911)
Total Carrying Amount of Assets Securing Debt Outstanding	$ (793)	$ (911)

Carrying amount of loans securing debt outstanding.

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The carrying amount of the consolidated Variable Interest Entity's assets included in the reporting entity's statement of financial position.

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