Capital Stock (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Class of Stock [Line Items]
Payments for Repurchase of Common Stock	$ 859	$ 25,309
Class A Common Stock
Class of Stock [Line Items]
Common Stock, Shares, Outstanding	21,926,590		21,613,885
Stock Repurchased and Retired During Period, Shares		948,242
Payments for Repurchase of Common Stock		$ 24,792
Stock Repurchase Program, Remaining Authorized Repurchase Amount	24,123
Class B Common Stock
Class of Stock [Line Items]
Common Stock, Shares, Outstanding	23,217,418		23,312,291