Common Stock and Treasury Stock - Additional Information (Details) - Class A Common Stock - Stock Buy back Program [Member] - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Common Stock [Line Items]
Stock Repurchase Program, Authorized Amount	$ 75,800,000		$ 75,800,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 18,800,000		$ 18,800,000
Stock Repurchased During Period, Shares	0	1,000	0	2,600
Stock Repurchased During Period, Value	$ 22,000	$ 22,000	$ 63,000	$ 63,000