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Fair Value Of Financial Instruments (Changes In Level 3 Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Detail) - Fair Value Inputs Level 3 [Member] - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015
Accounts Notes And Loans Receivable [Line Items] |  |
Beginning balance, fair value assets | $ 1,834 | $ 2,097
Realized gains/(losses), assets | (1) | (2)
Unrealized gains/(losses) included in earnings, assets | (16) | 11
Unrealized gains/(losses) included in OCI, assets | 32 | (2)
Foreign exchange recognized in OCI or earnings, assets | 5 | 6
Purchases, assets | 278 | 157
Issuances, assets | 0 | 0
Settlements, assets | (344) | (318)
Sales, assets | (109) | (32)
Transfers into level 3, assets | 17 | 43
Transfers out of level 3, assets | (144) | (126)
Ending balance, fair value assets | 1,552 | 1,834
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets | 8 | 14
Beginning balance, fair value liabilities | 1,531 | 1,200
Realized gains/(losses), liabilities | 43 | 28
Unrealized gains/(losses included in earnings, liabilities | (45) | (186)
Unrealized gains/(losses) included in OCI, liabilities | 0 | 0
Foreign exchange recognized in OCI or earnings, liabilities | (1) | (20)
Purchases, liabilities | 9 | 695
Issuances, liabilities | 0 | 0
Settlements, liabilities | (245) | (186)
Sales, liabilities | (631) | 0
Transfers into Level 3, liabilities | 0 | 0
Transfers out of Level 3, liabilities | 0 | 0
Ending balance, fair value liabilities | 661 | 1,531
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities | (38) | (192)
Residential Prime Financing Receivable [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Beginning balance, fair value assets | 1,185 | 1,431
Unrealized gains/(losses) included in earnings, assets | (11) | (13)
Settlements, assets | (258) | (233)
Ending balance, fair value assets | 916 | 1,185
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets | (11) | (13)
Other Loans Receivable [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Beginning balance, fair value assets | 107 |
Unrealized gains/(losses) included in earnings, assets | 4 | (1)
Purchases, assets | 146 | 108
Sales, assets | (107) |
Ending balance, fair value assets | 150 | 107
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets | 4 | (1)
Loan Repurchase Commitments [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Beginning balance, fair value assets | 396 | 379
Unrealized gains/(losses) included in earnings, assets | 8 | 17
Ending balance, fair value assets | 404 | 396
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets | 8 | 17
State and municipal bonds [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Beginning balance, fair value assets | 41 | 8
Purchases, assets | 122 | 45
Settlements, assets | (39) | (10)
Sales, assets | (1) |
Transfers into level 3, assets | 2 |
Transfers out of level 3, assets | (125) | (2)
Ending balance, fair value assets |  | 41
Foreign Government Debt [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Beginning balance, fair value assets | 2 | 6
Foreign exchange recognized in OCI or earnings, assets | (1) | (1)
Purchases, assets | 10 |
Settlements, assets | (10) |
Sales, assets |  | (3)
Transfers out of level 3, assets | (1) |
Ending balance, fair value assets |  | 2
Corporate Obligations [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Beginning balance, fair value assets | 7 | 10
Transfers into level 3, assets | 2 | 20
Transfers out of level 3, assets | (7) | (23)
Ending balance, fair value assets | 2 | 7
Corporate Obligations [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Beginning balance, fair value assets | 11 | 55
Unrealized gains/(losses) included in earnings, assets | (6) | (4)
Settlements, assets | (2) | (5)
Transfers into level 3, assets | 2 | 6
Transfers out of level 3, assets | (5) | (41)
Ending balance, fair value assets |  | 11
Residential Mortgage Backed Non Agency [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Beginning balance, fair value assets |  | 3
Unrealized gains/(losses) included in earnings, assets | (1) | 1
Settlements, assets |  | (1)
Transfers into level 3, assets | 1 | 2
Transfers out of level 3, assets |  | (5)
Commercial Mortgage Backed Securities [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Beginning balance, fair value assets |  | 2
Sales, assets | (1) |
Transfers into level 3, assets | 1 |
Transfers out of level 3, assets |  | (2)
Commercial Mortgage Backed Securities [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Unrealized gains/(losses) included in earnings, assets | (4) |
Transfers into level 3, assets | 4 |
Collateralized Debt Obligations [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Beginning balance, fair value assets | 29 | 87
Unrealized gains/(losses) included in OCI, assets | 18 | 3
Settlements, assets | (32) | (50)
Sales, assets |  | (8)
Transfers into level 3, assets |  | 1
Transfers out of level 3, assets |  | (4)
Ending balance, fair value assets | 15 | 29
Collateralized Debt Obligations [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Beginning balance, fair value assets | 1 | 5
Unrealized gains/(losses) included in earnings, assets |  | 5
Settlements, assets |  | (1)
Transfers into level 3, assets |  | 1
Transfers out of level 3, assets |  | (9)
Ending balance, fair value assets | 1 | 1
Other Asset Backed [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Beginning balance, fair value assets | 38 | 85
Realized gains/(losses), assets | (1) | (2)
Unrealized gains/(losses) included in earnings, assets | (1) |
Unrealized gains/(losses) included in OCI, assets | 14 | (5)
Purchases, assets |  | 4
Settlements, assets | (3) | (9)
Sales, assets |  | (21)
Transfers into level 3, assets |  | 12
Transfers out of level 3, assets | (3) | (26)
Ending balance, fair value assets | 44 | 38
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets | (1) |
Other Asset Backed [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Beginning balance, fair value assets | 6 | 26
Unrealized gains/(losses) included in earnings, assets | (7) | 2
Settlements, assets |  | (9)
Transfers into level 3, assets | 5 | 1
Transfers out of level 3, assets | (3) | (14)
Ending balance, fair value assets | 1 | 6
Medium Term Notes [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Beginning balance, fair value liabilities | 161 | 197
Unrealized gains/(losses included in earnings, liabilities | (3) | (16)
Foreign exchange recognized in OCI or earnings, liabilities | (1) | (20)
Settlements, liabilities | (56) |
Ending balance, fair value liabilities | 101 | 161
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities | (4) | (36)
Credit Derivatives [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Beginning balance, fair value liabilities | 85 | 244
Realized gains/(losses), liabilities | 43 | 28
Unrealized gains/(losses included in earnings, liabilities | (21) | (159)
Settlements, liabilities | (43) | (28)
Ending balance, fair value liabilities | 64 | 85
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities | (13) | (145)
Other Derivative Liabilities [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Beginning balance, fair value liabilities | 18 | 24
Unrealized gains/(losses included in earnings, liabilities | 2 | (6)
Ending balance, fair value liabilities | 20 | 18
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities | 2 | (6)
Variable Interest Entity Notes [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Beginning balance, fair value liabilities | 1,267 | 735
Unrealized gains/(losses included in earnings, liabilities | (23) | (5)
Purchases, liabilities | 9 | 695
Settlements, liabilities | (146) | (158)
Sales, liabilities | (631) |
Ending balance, fair value liabilities | 476 | 1,267
Change in unrealized gains/(losses) for the period included in earnings for liabilities still held, liabilities | (23) | (5)
Currency Derivatives [Member] | Variable Interest Entity Primary Beneficiary [Member] |  |
Accounts Notes And Loans Receivable [Line Items] |  |
Beginning balance, fair value assets | 11 |
Unrealized gains/(losses) included in earnings, assets | 2 | 4
Foreign exchange recognized in OCI or earnings, assets | 6 | 7
Ending balance, fair value assets | 19 | 11
Change in unrealized gains/(losses) for the period included in earnings for assets still held, assets | $ 8 | $ 11

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