Stockholders' Equity (Narrative) (Details) (Class A Common Stock [Member], USD $) Share data in Thousands, except Per Share data, unless otherwise specified	10 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Dec. 31, 2012 February 2012 Stock Repurchase Program [Member]	Dec. 31, 2012 February 2011 Stock Repurchase Program [Member]	Jun. 30, 2012 Repurchase of Equity [Member]	Jun. 30, 2011 Repurchase of Equity [Member]	Jun. 30, 2012 Repurchase of Equity [Member]	Jun. 30, 2011 Repurchase of Equity [Member]	Jun. 30, 2012 Stock Repurchase For Tax Withholding Member	Jun. 30, 2011 Stock Repurchase For Tax Withholding Member	Jun. 30, 2012 Stock Repurchase For Tax Withholding Member	Jun. 30, 2011 Stock Repurchase For Tax Withholding Member	Jun. 30, 2012 Restricted Stock [Member]	Dec. 31, 2011 Restricted Stock [Member]
Authorized repurchase of common stock	$ 600,000,000	$ 550,000,000
Stock repurchased and retired during period, shares			1,800	1,400	1,847	3,200	600	600	800	800
Weighted-average price for shares repurchased and retired, per share			$ 96.50	$ 91.60	$ 96.50	$ 88.50
Stock repurchased and retired during period, value			178,200,000	132,700,000	178,196,000	280,400,000	57,500,000	52,300,000	72,000,000	73,500,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount					$ 507,100,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number											11,696	9,540