Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2013

Stockholders' Equity Note [Abstract]

Schedule of change in the number of shares of Class A common stock

The following table sets forth the change in the number of shares of our Class A common stock outstanding during the nine months ended September 30, 2013 and during the fiscal year ended December 31, 2012:

	Nine Months Ended		Twelve Months Ended
	September 30, 2013		December 31, 2012
Shares outstanding as of beginning of period	84,395		92,433
Shares issued as part of equity-based compensation plans and the Employee    Stock Purchase Plan ("ESPP"), net of restricted stock units ("RSUs") surrendered	1,019		1,119
Shares repurchased into treasury stock	(226	)	(9,157	)
Shares outstanding as of end of period	85,188		84,395