Equity (Narrative) (Details) $ in Billions |
12 Months Ended | |
|---|---|---|
|
Dec. 11, 2015
shares
|
Dec. 31, 2016
USD ($)
vote
|
|
| Equity [Line Items] | ||
| Number of votes entitled of each class B common stock | vote | 15 | |
| Shares awarded per exchanged share (in shares) | shares | 1 | |
| New Authorization [Member] | ||
| Equity [Line Items] | ||
| Stock repurchase program, authorized amount | $ | $ 12 | |
| Class A Common Stock [Member] | ||
| Equity [Line Items] | ||
| Voting power | 66.67% | |
| Class B Common Stock [Member] | ||
| Equity [Line Items] | ||
| Voting power | 33.33% |