Equity (Narrative) (Details) $ in Billions |
12 Months Ended |
|---|---|
|
Dec. 31, 2018
USD ($)
vote
| |
| Equity [Line Items] | |
| Number of votes entitled of each class B common stock | vote | 15 |
| New Authorization [Member] | |
| Equity [Line Items] | |
| Stock repurchase program, authorized amount | $ 12.0 |
| Remaining authorized repurchase amount | $ 2.0 |
| Class A Common Stock [Member] | |
| Equity [Line Items] | |
| Voting power | 66.67% |
| Class B Common Stock [Member] | |
| Equity [Line Items] | |
| Voting power | 33.33% |