Common Stock and Treasury Stock (Details)	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Class A Common Stock
Common Stock [Line Items]
Balance, shares	6,370	6,360
Exercised options	5	10
Conversion of shares	1
Balance, shares	6,376	6,370
Class B Common Stock
Common Stock [Line Items]
Balance, shares	797	797
Exercised options	0	0
Conversion of shares	(1)
Balance, shares	796	797