Detail supporting the computation of basic and diluted earnings per common share was as follows for the three and nine months ended September 30, 2016 and 2015: | | | | | | | | | | | | | | | | | | Three months ended September 30, | | Nine months ended September 30, | | 2016 | | 2015 | | 2016 | | 2015 | | (dollars in millions, except per common share results; number of shares in thousands) | Net income available for common stockholders | $ | 450 |
| | $ | 314 |
| | $ | 1,015 |
| | $ | 1,175 |
| Weighted average outstanding shares of common stock
used to compute basic earnings per common share | 149,417 |
| | 148,889 |
| | 149,321 |
| | 149,617 |
| Dilutive effect of: | | | | | | | | Employee stock options | 210 |
| | 182 |
| | 216 |
| | 198 |
| Restricted stock | 1,277 |
| | 1,395 |
| | 1,332 |
| | 1,506 |
| Shares used to compute diluted earnings per common share | 150,904 |
| | 150,466 |
| | 150,869 |
| | 151,321 |
| Basic earnings per common share | $ | 3.01 |
| | $ | 2.11 |
| | $ | 6.80 |
| | $ | 7.85 |
| Diluted earnings per common share | $ | 2.98 |
| | $ | 2.09 |
| | $ | 6.73 |
| | $ | 7.77 |
| Number of antidilutive stock options and restricted stock
excluded from computation | 658 |
| | 320 |
| | 873 |
| | 451 |
|
|