Capital Stock (Details) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended				0 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Class A Common Stock	Dec. 31, 2013 Class A Common Stock	Jan. 24, 2014 Class A Common Stock 2006 Equity Compensation Plan [Member]	Jun. 30, 2014 Class A Common Stock Share Repurchase Program [Domain]	Jun. 30, 2014 Class B Common Stock	Dec. 31, 2013 Class B Common Stock
Class of Stock [Line Items]
Common Stock, Shares, Outstanding			20,269,171	19,868,018			23,985,841	24,287,045
Stock Repurchased and Retired During Period, Shares			325,418
Payments for Repurchase of Common Stock	$ 8,764	$ 448	$ 8,143
Stock Repurchase Program, Remaining Authorized Repurchase Amount						1,674,582
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized					1,500,000