Capital Stock (Details) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended			9 Months Ended			0 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Jul. 31, 2014	Sep. 30, 2014 Board of Directors	Sep. 30, 2014 Class A Common Stock	Dec. 31, 2013 Class A Common Stock	Jan. 24, 2014 Class A Common Stock 2006 Equity Compensation Plan	Sep. 30, 2014 Class A Common Stock Share Repurchase Program	Sep. 30, 2014 Class A Common Stock Board of Directors	Sep. 30, 2014 Class B Common Stock	Dec. 31, 2013 Class B Common Stock
Class of Stock [Line Items]
Common Stock, Shares, Outstanding					21,747,983	19,868,018				23,924,939	24,287,045
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned			$ 35,972
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period									24,581
Share-based Compensation Arrangement by Share-based Payment Award, Aggregate Value of Shares Issued				621
Stock Repurchased and Retired During Period, Shares					362,121
Payments for Repurchase of Common Stock	$ 9,736	$ 448			$ 9,078
Stock Repurchase Program, Remaining Authorized Repurchase Amount								1,637,879
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized							1,500,000