Capital Stock (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Class of Stock [Line Items]
Payments for Repurchase of Common Stock	$ 25,309	$ 15,264
Class A Common Stock
Class of Stock [Line Items]
Common Stock, Shares, Outstanding	21,007,483		21,698,594
Stock Repurchased and Retired During Period, Shares	948,242	565,875
Payments for Repurchase of Common Stock	$ 24,792	$ 14,674
Stock Repurchase Program, Remaining Authorized Repurchase Amount	51,758
Class B Common Stock
Class of Stock [Line Items]
Common Stock, Shares, Outstanding	23,700,002		23,729,631