Debt (Convertible Senior Notes) (Narrative) (Details) (USD $)	0 Months Ended	12 Months Ended			0 Months Ended		12 Months Ended		0 Months Ended	12 Months Ended		12 Months Ended
	Apr. 24, 2009	Dec. 31, 2011	Dec. 31, 2009	Dec. 31, 2010	Nov. 07, 2008 Convertible Senior Notes Due 2013 [Member]	May 16, 2008 Convertible Senior Notes Due 2013 [Member]	Dec. 31, 2011 Convertible Senior Notes Due 2013 [Member]	Dec. 31, 2010 Convertible Senior Notes Due 2013 [Member]	Apr. 24, 2009 Convertible Senior Notes Due 2014 [Member]	Dec. 31, 2011 Convertible Senior Notes Due 2014 [Member]	Dec. 31, 2010 Convertible Senior Notes Due 2014 [Member]	Dec. 31, 2011 1.875% Convertible Senior Notes [Member]	Dec. 31, 2011 4.0% Convertible Senior Notes [Member]
Short-term Debt [Line Items]
Debt instrument, issuance date						May 16, 2008			April 24, 2009
Convertible senior notes issued						$ 550,000,000
Equity component related to repurchases, convertible, effective interest rate						1.875%						1.875%	4.00%
Interest payable dates							May 1 and November 1		April 1 and October 1
Debt instrument, maturity date						May 01, 2013			Oct. 01, 2014
Convertible senior notes effective interest rate, maximum							9.40%
Conversion rate, in shares						$ 24.1196
Common stock principal amount						1,000
Per share conversion price						$ 41.46
Conversion premium						20.00%
Last reported selling price						$ 34.55
Debt instrument, face amount							535,000,000	550,000,000		500,000,000	500,000,000	15,000,000
Proceeds from issuance of convertible notes			488,195,000									17,000,000
Initial strike price						$ 41.46							$ 30.38
Proceeds from issuance of common stock warrants			98,491,000
Upper strike price						$ 67.37							$ 44.64
Convertible notes conversion criteria associated with common stock trading price		the last reported sale price of our Class A common stock for at least 20 trading days in the 30 consecutive trading day period ending on the last trading day of the preceding calendar quarter is more than 130% of the applicable conversion price per share of Class A common stock on the last day of such preceding calendar quarter
Convertible notes conversion criteria associated with common stock and convertible notes trading price		trading price per $1,000 principal amount of the Notes for each day in the measurement period was less than 95% of the product of the last reported sale price of Class A common stock
Terminated convertible note hedge transaction					55.00%
Common stock shares issuable		109,675,000		114,832,000	13,265,780
Carrying amount of the equity component							156,600,000			169,000,000
Principal balance							535,000,000	550,000,000		500,000,000	500,000,000	15,000,000
Debt discount							(50,030,000)	(86,030,000)		(102,388,000)	(131,537,000)
Carrying value							484,970,000	463,970,000		397,612,000	368,463,000
Issuance fee of convertible senior notes	11,700,000
Deferred financing fees	7,700,000
Financing fee recorded as a reduction to shareholders' equity	4,000,000
Debt instrument, convertible, conversion ratio						$ 24.1196
Common stock principal amount						$ 1,000
Coupon rate of notes										13.0