Treasury Stock (Details) (USD $)	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Treasury Stock [Roll Forward]
Shares purchased for minimum tax withholding, cost	$ 1,841,000	$ 0
Common Stock Class A
Equity, Class of Treasury Stock [Line Items]
Common stock repurchase program, maximum authorized amount	20,000,000
Treasury Stock [Roll Forward]
Treasury stock, shares, beginning of period	5,346,003
Treasury stock, cost, beginning of period	16,902,000
Treasury stock, average cost per share, beginning of period, in dollars per share	$ 3.16
Shares purchased for minimum tax withholding, shares	743,374
Shares purchased for minimum tax withholding, cost	1,841,000
Shares purchased for minimum tax withholding, average cost per share, in dollars per share	$ 2.48
Purchase of treasury stock, shares	1,797,309
Purchase of treasury stock, cost	4,516,000
Treasury stock acquired, average cost per share, in dollars per share	$ 2.51
Treasury stock, shares, end of period	7,886,686
Treasury stock, cost, end of period	$ 23,259,000
Treasury stock, average cost per share, end of period, in dollars per share	$ 2.95