Common and Preferred Shares and Warrants (Details) - shares shares in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Authorized shares and a reconciliation of common shares issued and outstanding | |||
| Common shares, authorized | 3,600 | 3,600 | 3,600 |
| Shares issued and outstanding at beginning of year | 969 | 1,023 | 1,064 |
| Repurchases of common shares | (70) | (59) | (49) |
| Other, primarily stock option exercises and RSAs granted | 5 | 5 | 8 |
| Shares issued and outstanding as of December 31 | 904 | 969 | 1,023 |
| Stockholders' Equity Note (Textuals) [Abstract] | |||
| Shares reserved for issuance under employee stock and employee benefit plans | 35 | ||