Common Stock and Treasury Stock - Information Relating to the Number of Shares of Our Common Stock Issued (Details) - shares shares in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2020
Class A Common Stock
Common Stock [Line Items]
Balance, shares	6,771	6,771
Conversion of shares		16
Issuance of restricted stock		0
Forfeiture of restricted stock (in shares)	(2)	(2)
Balance, shares	6,769	6,785
Class B Common Stock
Common Stock [Line Items]
Balance, shares	954	954
Conversion of shares		(16)
Issuance of restricted stock		0
Forfeiture of restricted stock (in shares)	0	0
Balance, shares	954	938