Stockholders' Equity - Changes in Class A Common Stock (Details) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Change in the number of shares of Class A common stock outstanding
Shares outstanding as of end of period	85,240	84,395
Class A Common Stock
Change in the number of shares of Class A common stock outstanding
Shares outstanding as of beginning of period	84,395	92,433
Shares issued as part of equity-based compensation plans and the ESPP, net of shares surrendered	1,121	1,119
Shares repurchased into treasury stock	(276)	(9,157)
Shares outstanding as of end of period	85,240	84,395