Condensed Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement Of Stockholders Equity [Abstract]
Class A common stock dividends per share	$ 0.47	$ 0.44	$ 1.88	$ 2.59
Tax expense (benefit) related to delivery of Class A Common Stock in connection with share-based incentive compensation	$ (61)	$ 233	$ (4,419)	$ 7,745