Debt (1.875% Convertible Senior Notes Due 2013) (Narrative) (Details) (USD $)	12 Months Ended	0 Months Ended		12 Months Ended			3 Months Ended	0 Months Ended		12 Months Ended
	Dec. 31, 2013	Feb. 22, 2013 1.875% Convertible Senior Notes [Member]	May 16, 2008 1.875% Convertible Senior Notes [Member]	Dec. 31, 2013 1.875% Convertible Senior Notes [Member]	Apr. 18, 2013 1.875% Convertible Senior Notes [Member]	Feb. 01, 2013 1.875% Convertible Senior Notes [Member]	Sep. 30, 2013 1.875% Convertible Senior Notes [Member] Lehman Brothers [Member]	Feb. 22, 2013 Class A Common Stock [Member] 1.875% Convertible Senior Notes [Member]	May 16, 2008 Class A Common Stock [Member] 1.875% Convertible Senior Notes [Member]	Dec. 31, 2013 Class A Common Stock [Member] 1.875% Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, issuance date			May 16, 2008
Convertible senior notes issued			$ 550,000,000
Debt instrument, interest rate, stated percentage			1.875%	1.875%	1.875%
Interest payable dates			May 1 and November 1
Debt instrument, maturity date			May 01, 2013	May 01, 2013
Conversion rate									0.0241196
Per share conversion price									$ 41.46
Conversion premium									20.00%
Last reported selling price									$ 34.55
Issuance of stock for conversion of debt, amount	18,159,000	18,100,000
Debt conversion, common stock issued		437,134
Common stock received								71,054
Settlement of future conversion obligations						100.00%
Additional conversion notices aggregate value				450,600,000
Converted Notes held by subsidiary				81,200,000
Convertible indenture notes				1.76402
Convertible notes aggregate value				794,800,000
Aggregate principal amount				142,000
Proceeds from settlement of convertible note hedges	182,855,000			182,900,000
Company paid in cash to settle warrants	97,912,000			97,900,000
Common stock warrants issued										392,532
Initial strike price of warrants				$ 67.37
Gain on a sale of a bankruptcy claim							$ 27,300,000