Consolidated Balance Sheets Parentheticals - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Class A Common Shares [Member]
Common Stock, par value per share	$ 0.01	$ 0.01
Common Stock, votes per share	1	1
Common Stock, shares authorized	180,000,000	180,000,000
Common Stock, shares issued	74,512,436	74,162,972
Common Stock, shares outstanding	61,668,015	61,362,665
Treasury Stock, shares	12,844,421	12,800,307
Class B Common Shares [Member]
Common Stock, par value per share	$ 0.01	$ 0.01
Common Stock, votes per share	10	10
Common Stock, shares authorized	30,000,000	30,000,000
Common Stock, shares issued	713,138	758,138
Common Stock, shares outstanding	713,138	758,138