Quarterly report pursuant to Section 13 or 15(d)

Stock Incentive Plans (Narrative) (Details)

Stock Incentive Plans (Narrative) (Details) - Executive Officers [Member] - Restricted Stock [Member] - Class B Common Stock [Member]
$ in Millions
Jan. 08, 2019
USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Number of shares granted 1,923,975
Number of shares vested 481,000
Aggregate fair value on grant date | $ $ 11.8
Number of annual installments vested | item 4