Capital Stock (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Class of Stock [Line Items]
Payments for Repurchase of Common Stock	$ 26,119	$ 20,548
Class A Common Stock
Class of Stock [Line Items]
Common Stock, Shares, Outstanding	21,459,481		21,698,594
Stock Repurchased and Retired During Period, Shares	975,877	765,875
Payments for Repurchase of Common Stock	$ 25,525	$ 19,921
Stock Repurchase Program, Remaining Authorized Repurchase Amount	24,123
Class B Common Stock
Class of Stock [Line Items]
Common Stock, Shares, Outstanding	23,420,517		23,729,631