Condensed Consolidated Statements of Changes in Equity (Unaudited) (Parenthetical) - $ / shares
|9 Months Ended|
Sep. 30, 2018
Sep. 30, 2017
|Class A Common Stock|
|Common stock dividends, per share||$ 0.42||$ 0.36|
Aggregate dividends paid during the period for each share of common stock outstanding.
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef