Stock-based Compensation (Schedule of Stock Option Activities) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions | 9 Months Ended | 12 Months Ended |
Sep. 30, 2021 | Dec. 31, 2020 |
Stock Options [Member] | | |
Stock Option Activity [Abstract] | | |
Stock options, shares outstanding at January 1, 2021 | 2,569 | |
Stock options, shares granted | 387 | |
Stock options, shares exercised | (356) | |
Stock options, shares forfeited or expired | (90) | |
Stock options, shares outstanding at September 30, 2021 | 2,510 | 2,569 |
Stock options, shares vested or expected to vest at September 30, 2021 | 2,486 | |
Stock options, shares exercisable at September 30, 2021 | 1,731 | |
Stock options weighted-average exercise price, outstanding at January 1, 2021 | $ 132.49 | |
Stock options weighted-average exercise price, granted | 204.45 | |
Stock options weighted-average exercise price, exercised | 121.82 | |
Stock options weighted-average exercise price, forfeited or expired | 159.45 | |
Stock options weighted-average exercise price, outstanding at September 30, 2021 | 144.13 | $ 132.49 |
Stock options weighted-average exercise price, vested or expected to vest at September 30, 2021 | 143.82 | |
Stock options weighted-average exercise price, options exercisable at September 30, 2021 | $ 123.54 | |
Stock options weighted-average remaining contractual term in years, outstanding at January 1, 2021 | 6 years 2 months 12 days | 6 years 4 months 24 days |
Stock options weighted-average remaining contractual term in years, outstanding at September 30, 2021 | 6 years 2 months 12 days | 6 years 4 months 24 days |
Stock options weighted-average remaining contractual term in years, vested or expected to vest at September 30, 2021 | 6 years 2 months 12 days | |
Stock options weighted-average remaining contractual term in years, options exercisable at September 30, 2021 | 5 years 1 month 6 days | |
Stock options aggregate intrinsic value, outstanding at January 1, 2021 | $ 195 | |
Stock options aggregate intrinsic value, outstanding at September 30, 2021 | 133 | $ 195 |
Stock options aggregate intrinsic value, vested or expected to vest at September 30, 2021 | 133 | |
Stock options aggregate intrinsic value, options exercisable at September 30, 2021 | $ 125 | |
Retention Awards [Member] | | |
Awards Activity [Abstract] | | |
Awards, shares nonvested at January 1, 2021 | 1,476 | |
Awards, shares granted | 289 | |
Awards, shares vested | (414) | |
Awards, shares forfeited | (53) | |
Awards, shares nonvested at September 30, 2021 | 1,298 | 1,476 |
Awards weighted-average grant-date fair value, nonvested at January 1, 2021 | $ 141.06 | |
Awards weighted-average grant-date fair value, granted | 205.10 | |
Awards weighted-average grant-date fair value, vested | 108.32 | |
Awards weighted-average grant-date fair value, forfeited | 162.23 | |
Awards weighted-average grant-date fair value, nonvested at September 30, 2021 | $ 164.90 | $ 141.06 |
Performance Retention Awards [Member] | | |
Awards Activity [Abstract] | | |
Awards, shares nonvested at January 1, 2021 | 773 | |
Awards, shares granted | 227 | |
Awards, shares vested | (147) | |
Awards, shares unearned | (165) | |
Awards, shares forfeited | (41) | |
Awards, shares nonvested at September 30, 2021 | 647 | 773 |
Awards weighted-average grant-date fair value, nonvested at January 1, 2021 | $ 148.17 | |
Awards weighted-average grant-date fair value, granted | 204.45 | |
Awards weighted-average grant-date fair value, vested | 132.66 | |
Awards weighted-average grant-date fair value, unearned | 135.57 | |
Awards weighted-average grant-date fair value, forfeited | 183.55 | |
Awards weighted-average grant-date fair value, nonvested at September 30, 2021 | $ 172.41 | $ 148.17 |