Stockholders' Equity (Schedule of Share Repurchase Authorizations) (Details) - Class A Common Stock - USD ($) $ / shares in Units, shares in Millions, $ in Millions |
1 Months Ended | 12 Months Ended | 13 Months Ended | 25 Months Ended | 37 Months Ended | |||||
|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2020 |
Dec. 31, 2020 |
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Class of Stock [Line Items] | ||||||||||
| Board Authorization | $ 28,500 | $ 28,500 | $ 28,500 | $ 28,500 | $ 28,500 | |||||
| Dollar-value of shares repurchased | 4,473 | $ 6,497 | $ 4,933 | |||||||
| Remaining authorization | 9,831 | $ 9,831 | $ 8,304 | $ 6,801 | 9,831 | 9,831 | $ 9,831 | $ 8,304 | ||
| Shares repurchased | 14.3 | 26.4 | 26.2 | 87.9 | ||||||
| Average price paid per share | $ 312.68 | $ 245.89 | $ 188.26 | $ 212.41 | ||||||
| December 2016 Share Repurchase Plan | ||||||||||
| Class of Stock [Line Items] | ||||||||||
| Board Authorization | $ 4,000 | |||||||||
| Dollar-value of shares repurchased | $ 0 | $ 1,234 | ||||||||
| Remaining authorization | $ 0 | $ 0 | $ 0 | |||||||
| Shares repurchased | 0.0 | 0.0 | 7.2 | 28.2 | ||||||
| Average price paid per share | $ 0 | $ 0 | $ 171.11 | $ 141.99 | ||||||
| December 2017 Share Repurchase Plan | ||||||||||
| Class of Stock [Line Items] | ||||||||||
| Board Authorization | $ 4,000 | |||||||||
| Dollar-value of shares repurchased | $ 0 | $ 301 | $ 3,699 | |||||||
| Remaining authorization | 0 | $ 0 | $ 0 | $ 301 | 0 | 0 | $ 0 | $ 0 | ||
| Shares repurchased | 0.0 | 1.6 | 19.0 | 20.6 | ||||||
| Average price paid per share | $ 0 | $ 188.38 | $ 194.77 | $ 194.27 | ||||||
| December 2018 Share Repurchase Plan | ||||||||||
| Class of Stock [Line Items] | ||||||||||
| Board Authorization | $ 6,500 | |||||||||
| Dollar-value of shares repurchased | $ 304 | $ 6,196 | ||||||||
| Remaining authorization | 0 | $ 0 | $ 304 | $ 6,500 | 0 | $ 0 | $ 0 | 304 | ||
| Shares repurchased | 1.0 | 24.8 | 25.8 | |||||||
| Average price paid per share | $ 304.89 | $ 249.58 | $ 251.72 | |||||||
| December 2019 Share Repurchase Plan | ||||||||||
| Class of Stock [Line Items] | ||||||||||
| Board Authorization | $ 8,000 | 8,000 | ||||||||
| Dollar-value of shares repurchased | $ 4,169 | |||||||||
| Remaining authorization | 3,831 | $ 3,831 | $ 8,000 | $ 3,831 | $ 3,831 | 3,831 | $ 8,000 | |||
| Shares repurchased | 13.3 | 13.3 | ||||||||
| Average price paid per share | $ 313.26 | $ 313.26 | ||||||||
| December 2020 Share Repurchase Plan | ||||||||||
| Class of Stock [Line Items] | ||||||||||
| Board Authorization | 6,000 | $ 6,000 | $ 6,000 | 6,000 | 6,000 | |||||
| Remaining authorization | $ 6,000 | $ 6,000 | $ 6,000 | $ 6,000 | $ 6,000 | |||||
| Shares repurchased | 0.0 | |||||||||
| Average price paid per share | $ 0 | |||||||||