Debt - Senior Notes and Contingent Convertible Senior Notes Purchased Narrative (Details) (USD $)	9 Months Ended				9 Months Ended																						9 Months Ended			9 Months Ended					9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014 Senior Notes [Member]	Sep. 30, 2013 Senior Notes [Member]	Apr. 24, 2014 Senior Notes [Member]	Sep. 30, 2013 Senior Notes [Member] Premium on Extinguishment of Senior Note Debt [Member]	Sep. 30, 2013 Senior Notes [Member] Unamortized Deferred Charges on Extinguishment of Senior Note Debt [Member]	Sep. 30, 2014 Minimum [Member] Senior Notes [Member]	Sep. 30, 2014 Maximum [Member] Senior Notes [Member]	Sep. 30, 2014 2.5% Contingent Convertible Senior Notes due 2037 [Member] Senior Notes [Member]	Dec. 31, 2013 2.5% Contingent Convertible Senior Notes due 2037 [Member] Senior Notes [Member]	Sep. 30, 2014 2.75% Contingent Convertible Senior Notes Due 2035 [Member] Senior Notes [Member]	Dec. 31, 2013 2.75% Contingent Convertible Senior Notes Due 2035 [Member] Senior Notes [Member]	Sep. 30, 2014 2.25% Contingent Convertible Senior Notes Due 2038 [Member] Senior Notes [Member]	Dec. 31, 2013 2.25% Contingent Convertible Senior Notes Due 2038 [Member] Senior Notes [Member]	Sep. 30, 2014 4.875% Senior Notes due 2022 [Member] Senior Notes [Member]	Dec. 31, 2013 4.875% Senior Notes due 2022 [Member] Senior Notes [Member]	Sep. 30, 2014 3.25% Senior Notes due 2016 [Member] Senior Notes [Member]	Dec. 31, 2013 3.25% Senior Notes due 2016 [Member] Senior Notes [Member]	Sep. 30, 2013 3.25% Senior Notes due 2016 [Member] Senior Notes [Member]	Sep. 30, 2014 5.375% Senior Notes due 2021 [Member] Senior Notes [Member]	Dec. 31, 2013 5.375% Senior Notes due 2021 [Member] Senior Notes [Member]	Sep. 30, 2013 5.375% Senior Notes due 2021 [Member] Senior Notes [Member]	Sep. 30, 2014 5.75% Senior Notes due 2023 [Member] Senior Notes [Member]	Dec. 31, 2013 5.75% Senior Notes due 2023 [Member] Senior Notes [Member]	Sep. 30, 2013 5.75% Senior Notes due 2023 [Member] Senior Notes [Member]	Sep. 30, 2013 7.625% Senior Notes Due 2013 [Member] Senior Notes [Member]	Sep. 30, 2014 6.875% Senior Notes Due 2018 [Member] Senior Notes [Member]	Dec. 31, 2013 6.875% Senior Notes Due 2018 [Member] Senior Notes [Member]	Sep. 30, 2013 6.875% Senior Notes Due 2018 [Member] Senior Notes [Member]	Sep. 30, 2014 6.875% Senior Notes Due 2018 [Member] Senior Notes [Member] Premium on Extinguishment of Senior Note Debt [Member]	Sep. 30, 2014 6.875% Senior Notes Due 2018 [Member] Senior Notes [Member] Unamortized Deferred Charges on Extinguishment of Senior Note Debt [Member]	Sep. 30, 2014 9.5% Senior Notes Due 2015 [Member] Senior Notes [Member]	Dec. 31, 2013 9.5% Senior Notes Due 2015 [Member] Senior Notes [Member]	Sep. 30, 2013 9.5% Senior Notes Due 2015 [Member] Senior Notes [Member]	Sep. 30, 2014 9.5% Senior Notes Due 2015 [Member] Senior Notes [Member] Premium on Extinguishment of Senior Note Debt [Member]	Sep. 30, 2014 9.5% Senior Notes Due 2015 [Member] Senior Notes [Member] Unamortized Discount on Extinguishment of Senior Note Debt [Member]	Sep. 30, 2014 9.5% Senior Notes Due 2015 [Member] Senior Notes [Member] Unamortized Deferred Charges on Extinguishment of Senior Note Debt [Member]	Sep. 30, 2013 6.775% Senior Notes Due 2019 [Member] Senior Notes [Member]	Sep. 30, 2013 6.775% Senior Notes Due 2019 [Member] Senior Notes [Member] Unamortized Discount on Extinguishment of Senior Note Debt [Member]	Sep. 30, 2013 6.775% Senior Notes Due 2019 [Member] Senior Notes [Member] Unamortized Deferred Charges on Extinguishment of Senior Note Debt [Member]
Long-Term Debt Instrument [Line Items]
Equity Method Investment, Ownership Percentage		100.00%
Debt Instrument, Interest Rate, Stated Percentage									2.50%		2.75%		2.25%		4.875%		3.25%		3.25%	5.375%		5.375%	5.75%		5.75%	7.625%	6.875%		6.875%			9.50%						6.775%
Debt Instrument, Interest Rate, Effective Percentage									8.00%		6.86%		8.00%
Debt Instrument, Face Amount			$ 2,300,000,000
Long-term Debt, Gross	1,500,000,000	3,000,000,000		3,000,000,000			50,000,000	75,000,000	1,168,000,000	1,168,000,000	396,000,000	396,000,000	347,000,000	347,000,000	1,500,000,000	0	500,000,000	500,000,000	500,000,000	700,000,000	700,000,000	700,000,000	1,100,000,000	1,100,000,000	1,100,000,000	247,000,000	0	97,000,000				0	1,265,000,000
Proceeds from issuance of senior notes, net of discount and offering costs	3,460,000,000	2,966,000,000	2,274,000,000
Debt Instrument, Repurchase Amount			405,000,000																							221,000,000
Debt Instrument, Repurchased Face Amount																										217,000,000	97,000,000		377,000,000			1,265,000,000		1,454,000,000				1,300,000,000
Gain (Loss) on Repurchase of Debt Instrument			$ 37,000,000		$ 32,000,000	$ 5,000,000																					$ 6,000,000			$ 5,000,000	$ 1,000,000	$ 99,000,000			$ 87,000,000	$ 9,000,000	$ 3,000,000	$ 33,000,000	$ 14,000,000	$ 19,000,000