Fair Value Measurements (Estimated Fair Values Of Financial Instruments Not Recorded At Fair Value In Their Entirety On A Recurring Basis) (Details) - USD ($) $ in Millions |
Mar. 31, 2018 |
Dec. 31, 2017 |
| Cash and due from banks |
|
$ 1,173
|
$ 1,438
|
| Interest-bearing deposits with banks |
|
5,663
|
4,407
|
| Investment securities held-to-maturity |
|
0
|
1,266
|
| Total loans, net of allowance for loan losses |
|
48,542
|
48,461
|
| Demand deposits (noninterest-bearing) |
|
30,961
|
32,071
|
| Customer certificates of deposit |
|
2,071
|
2,165
|
| Total deposits |
|
57,635
|
57,903
|
| Short-term borrowings |
|
48
|
10
|
| Medium- and long-term debt |
|
5,594
|
4,622
|
| Carrying Amount |
|
|
|
| Cash and due from banks |
|
1,173
|
1,438
|
| Interest-bearing deposits with banks |
|
5,663
|
4,407
|
| Investment securities held-to-maturity |
|
|
1,266
|
| Loans held-for-sale |
|
2
|
4
|
| Total loans, net of allowance for loan losses |
[1] |
48,542
|
48,461
|
| Customers' liability on acceptances outstanding |
|
2
|
2
|
| Restricted equity investments |
|
248
|
207
|
| Nonmarketable equity securities |
[2] |
6
|
6
|
| Demand deposits (noninterest-bearing) |
|
30,961
|
32,071
|
| Interest-bearing deposits |
|
24,603
|
23,667
|
| Customer certificates of deposit |
|
2,071
|
2,165
|
| Total deposits |
|
57,635
|
57,903
|
| Short-term borrowings |
|
48
|
10
|
| Acceptances outstanding |
|
2
|
2
|
| Medium- and long-term debt |
|
5,594
|
4,622
|
| Credit-related financial instruments |
|
(68)
|
(67)
|
| Estimated Fair Value |
|
|
|
| Cash and due from banks |
|
1,173
|
1,438
|
| Interest-bearing deposits with banks |
|
5,663
|
4,407
|
| Investment securities held-to-maturity |
|
|
1,246
|
| Loans held-for-sale |
|
2
|
4
|
| Total loans, net of allowance for loan losses |
[1] |
48,345
|
48,153
|
| Customers' liability on acceptances outstanding |
|
2
|
2
|
| Restricted equity investments |
|
248
|
207
|
| Nonmarketable equity securities |
[2] |
9
|
9
|
| Demand deposits (noninterest-bearing) |
|
30,961
|
32,071
|
| Interest-bearing deposits |
|
24,603
|
23,667
|
| Customer certificates of deposit |
|
2,041
|
2,142
|
| Total deposits |
|
57,605
|
57,880
|
| Short-term borrowings |
|
48
|
10
|
| Acceptances outstanding |
|
2
|
2
|
| Medium- and long-term debt |
|
5,604
|
4,636
|
| Credit-related financial instruments |
|
(68)
|
(67)
|
| Level 1 | Estimated Fair Value |
|
|
|
| Cash and due from banks |
|
1,173
|
1,438
|
| Interest-bearing deposits with banks |
|
5,663
|
4,407
|
| Investment securities held-to-maturity |
|
|
0
|
| Loans held-for-sale |
|
0
|
0
|
| Total loans, net of allowance for loan losses |
[1] |
0
|
0
|
| Customers' liability on acceptances outstanding |
|
2
|
2
|
| Restricted equity investments |
|
248
|
207
|
| Demand deposits (noninterest-bearing) |
|
0
|
0
|
| Interest-bearing deposits |
|
0
|
0
|
| Customer certificates of deposit |
|
0
|
0
|
| Total deposits |
|
0
|
0
|
| Short-term borrowings |
|
48
|
10
|
| Acceptances outstanding |
|
2
|
2
|
| Medium- and long-term debt |
|
0
|
0
|
| Credit-related financial instruments |
|
0
|
0
|
| Level 2 | Estimated Fair Value |
|
|
|
| Cash and due from banks |
|
0
|
0
|
| Interest-bearing deposits with banks |
|
0
|
0
|
| Investment securities held-to-maturity |
|
|
1,246
|
| Loans held-for-sale |
|
2
|
4
|
| Total loans, net of allowance for loan losses |
[1] |
0
|
0
|
| Customers' liability on acceptances outstanding |
|
0
|
0
|
| Restricted equity investments |
|
0
|
0
|
| Demand deposits (noninterest-bearing) |
|
30,961
|
32,071
|
| Interest-bearing deposits |
|
24,603
|
23,667
|
| Customer certificates of deposit |
|
2,041
|
2,142
|
| Total deposits |
|
57,605
|
57,880
|
| Short-term borrowings |
|
0
|
0
|
| Acceptances outstanding |
|
0
|
0
|
| Medium- and long-term debt |
|
5,604
|
4,636
|
| Credit-related financial instruments |
|
0
|
0
|
| Level 3 | Estimated Fair Value |
|
|
|
| Cash and due from banks |
|
0
|
0
|
| Interest-bearing deposits with banks |
|
0
|
0
|
| Investment securities held-to-maturity |
|
|
0
|
| Loans held-for-sale |
|
0
|
0
|
| Total loans, net of allowance for loan losses |
[1] |
48,345
|
48,153
|
| Customers' liability on acceptances outstanding |
|
0
|
0
|
| Restricted equity investments |
|
0
|
0
|
| Demand deposits (noninterest-bearing) |
|
0
|
0
|
| Interest-bearing deposits |
|
0
|
0
|
| Customer certificates of deposit |
|
0
|
0
|
| Total deposits |
|
0
|
0
|
| Short-term borrowings |
|
0
|
0
|
| Acceptances outstanding |
|
0
|
0
|
| Medium- and long-term debt |
|
0
|
0
|
| Credit-related financial instruments |
|
(68)
|
(67)
|
| Nonrecurring |
|
|
|
| Total loans, net of allowance for loan losses |
|
$ 106
|
$ 116
|
|
|