Debt - Senior Notes and Contingent Convertible Senior Notes Purchased Narrative (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended					12 Months Ended											12 Months Ended			3 Months Ended						12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Senior Notes	Dec. 31, 2012 Senior Notes	Dec. 31, 2012 Term Loan [Member]	Dec. 31, 2013 Minimum Senior Notes	Dec. 31, 2013 Minimum COO Senior Notes [Member]	Dec. 31, 2013 2.5% Contingent Convertible Senior Notes due 2037 Senior Notes	Dec. 31, 2012 2.5% Contingent Convertible Senior Notes due 2037 Senior Notes	Dec. 31, 2013 2.75% Contingent Convertible Senior Notes Due 2035 Senior Notes	Dec. 31, 2012 2.75% Contingent Convertible Senior Notes Due 2035 Senior Notes	Dec. 31, 2013 2.25% Contingent Convertible Senior Notes Due 2038 Senior Notes	Dec. 31, 2012 2.25% Contingent Convertible Senior Notes Due 2038 Senior Notes	Dec. 31, 2013 3.25% Senior Notes due 2016 Senior Notes	Dec. 31, 2012 3.25% Senior Notes due 2016 Senior Notes	Dec. 31, 2013 6.775% Senior Notes Due 2019 Senior Notes	Dec. 31, 2012 6.775% Senior Notes Due 2019 Senior Notes	Dec. 31, 2013 7.625% Senior Notes Due 2013	Sep. 30, 2013 7.625% Senior Notes Due 2013 Senior Notes	Dec. 31, 2013 7.625% Senior Notes Due 2013 Senior Notes	Dec. 31, 2012 7.625% Senior Notes Due 2013 Senior Notes	Dec. 31, 2013 6.625% Senior Notes Due 2019	Dec. 31, 2013 6.625% Senior Notes Due 2019 Senior Notes	Dec. 31, 2012 6.625% Senior Notes Due 2019 Senior Notes	Dec. 31, 2013 6.625% Senior Notes Due 2019 COO Senior Notes [Member]	Dec. 31, 2013 5.375% Senior Notes due 2021 [Member] Senior Notes	Dec. 31, 2012 5.375% Senior Notes due 2021 [Member] Senior Notes	Dec. 31, 2013 5.75% Senior Notes due 2023 [Member] Senior Notes	Dec. 31, 2012 5.75% Senior Notes due 2023 [Member] Senior Notes	Dec. 31, 2013 6.875% Senior Notes Due 2018 Senior Notes	Dec. 31, 2012 6.875% Senior Notes Due 2018 Senior Notes
Long-Term Debt Instrument [Line Items]
Equity Method Investment, Ownership Percentage	50.00%			100.00%
Debt Outstanding Principal Amount							$ 50
Debt Instrument, Interest Rate, Stated Percentage									2.50%		2.75%		2.25%		3.25%		6.775%		7.625%		7.625%		6.625%	6.625%			5.375%		5.75%		6.875%
Debt Instrument, Interest Rate, Effective Percentage									8.00%		6.86%		8.00%
Proceeds from issuance of senior notes, net of discount and offering costs	2,274	1,263	1,614	2,274														1,263
Long-term Debt, Gross	12,886	12,620		2,300				50	1,168	1,168	396	396	347	347	500	0	0	1,300			0	464		650	650		700	0	1,100	0	97	474
Long-term Debt	13,230																	1,300
Write off of Deferred Debt Issuance Cost				5		86											19
Debt Instrument, Unamortized Discount				303	376	114															1
Write-off of Debt Discount				32													14
Repayments of Notes Payable																				247
Debt Instrument, Repurchase Amount				405																	221
Debt Instrument, Repurchased Face Amount																					217										377
Gain (Loss) on Repurchase of Debt Instrument				$ 37													$ 33
Debt Instrument Principal Amount Redeemed Percent																										35.00%