Stock Compensation - Effects on Cash Flows (Details) - USD ($) $ in Millions |
3 Months Ended | 12 Months Ended | |||||||
|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2016 |
Sep. 30, 2016 |
Jun. 30, 2016 |
Mar. 31, 2016 |
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|||
| Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] | |||||||||
| Proceeds from common stock transactions | [1] | $ 472 | $ 396 | $ 554 | |||||
| Tax benefit realized from stock compensation | 255 | 171 | 218 | ||||||
| Reduction to deferred income tax asset | (105) | (81) | (108) | ||||||
| Excess tax benefit for stock compensation | $ 17 | $ 50 | $ 40 | $ 43 | $ 150 | $ 90 | $ 110 | ||
| |||||||||