Condensed Consolidated Statements of Changes in Equity (Unaudited) (Parenthetical) - $ / shares
|3 Months Ended|
Mar. 31, 2018
Mar. 31, 2017
|Class A Common Stock|
|Common stock dividends, per share||$ 0.14||$ 0.12|
Aggregate dividends paid during the period for each share of common stock outstanding.
Reference 1: http://www.xbrl.org/2003/role/presentationRef