DEBT - Schedule of Long-term Debt Outstanding (Details) (USD $)	1 Months Ended	3 Months Ended	1 Months Ended
	Sep. 30, 2014	Mar. 31, 2015	Oct. 31, 2014	Dec. 31, 2014	Dec. 31, 2008
Debt Instrument [Line Items]
Total long-term debt		$ 3,824,000,000		$ 3,825,000,000
Senior Notes
Debt Instrument [Line Items]
Total long-term debt		3,824,000,000		3,825,000,000
Proceeds from issuance of debt, net of underwriters' discount and commission and offering expenses	1,730,000,000
Redemption price, percentage		100.00%
Unamortized discount (premium)		31,000,000		32,000,000	103,000,000
Senior Notes | 6.45% Senior Notes due June 2016
Debt Instrument [Line Items]
Redemption price, percentage			100.00%
Extinguishment of debt, amount paid			560,000,000
Loss on extinguishment of debt			37,000,000
Unamortized discount (premium)			12,000,000
Senior Notes | $500 million, 7.20% due June 15, 2018
Debt Instrument [Line Items]
Stated interest rate		7.20%		7.20%
Face amount		500,000,000		500,000,000
Total long-term debt		504,000,000		504,000,000
Senior Notes | $300 million, 6.30% due August 1, 2018
Debt Instrument [Line Items]
Stated interest rate		6.30%		6.30%
Face amount		300,000,000		300,000,000
Total long-term debt		311,000,000		312,000,000
Senior Notes | $400 million, 2.625% due October 1, 2019
Debt Instrument [Line Items]
Stated interest rate		2.625%		2.625%
Face amount		400,000,000		400,000,000
Total long-term debt		400,000,000		400,000,000
Senior Notes | $600 million, 3.15% due December 1, 2022
Debt Instrument [Line Items]
Stated interest rate		3.15%		3.15%
Face amount		600,000,000		600,000,000
Total long-term debt		598,000,000		598,000,000
Senior Notes | $600 million, 3.85% due October 1, 2024
Debt Instrument [Line Items]
Stated interest rate		3.85%		3.85%
Face amount		600,000,000		600,000,000
Total long-term debt		599,000,000		599,000,000
Senior Notes | $250 million, 8.15% due June 15, 2038
Debt Instrument [Line Items]
Stated interest rate		8.15%		8.15%
Face amount		250,000,000		250,000,000
Total long-term debt		266,000,000		266,000,000
Senior Notes | $400 million, 4.625% due December 1, 2042
Debt Instrument [Line Items]
Stated interest rate		4.625%		4.625%
Face amount		400,000,000		400,000,000
Total long-term debt		400,000,000		400,000,000
Senior Notes | $750 million, 4.95% due October 1, 2044
Debt Instrument [Line Items]
Stated interest rate		4.95%		4.95%
Face amount		750,000,000		750,000,000
Total long-term debt		$ 746,000,000		$ 746,000,000