Equity - Activity for Class B Common Stock and Treasury Stock (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance (in shares)	9,226,413	8,294,433	8,375,077	8,702,074
Stock Award Activity (in shares)	(22,500)	(7,500)	(728,831)	(528,574)
Purchase of Treasury Stock (in shares)	866,900	79,592	2,424,567	193,025
Ending Balance (in shares)	10,070,813	8,366,525	10,070,813	8,366,525
Class B Shares
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance (in shares)	100,279,043	101,211,023	101,130,379	100,803,382
Stock Award Activity (in shares)	22,500	7,500	728,831	528,574
Purchase of Treasury Stock (in shares)	(866,900)	(79,592)	(2,424,567)	(193,025)
Ending Balance (in shares)	99,434,643	101,138,931	99,434,643	101,138,931
Purchase of Treasury Stock (in shares)			2,400,000