Stockholders Equity (Share Repurchase Program) (Details) (Common Class A, USD $)	12 Months Ended		3 Months Ended	6 Months Ended
	Dec. 31, 2013 2011 Stock Repurchase Program	Nov. 08, 2011 2011 Stock Repurchase Program	Jun. 30, 2014 2013 Stock Repurchase Program	Jun. 30, 2014 2013 Stock Repurchase Program	Nov. 12, 2013 2013 Stock Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount		$ 50,000,000			$ 60,000,000
Treasury stock acquisition	$ 35,600,000		$ 9,300,000	$ 14,200,000
Stock repurchase program, shares acquired during period			175,359	266,337
Stock repurchase program, shares acquired during period, weighted-average cost per share			$ 52.82	$ 53.49