Debt - Long-Term Debt Table (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Dec. 31, 2006
Long-Term Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount	$ (210)	$ (231)
Long-term Debt	11,508	11,535
Current maturities of long-term debt, net	(885)	(381)
Long-term debt, net	10,623	11,154
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed	100.00%
Debt Instrument, Convertible, Terms of Conversion Feature	5 days
Credit Facility Commitment Period	10 years
Percentage Of Principal Amount Of Notes For Repurchase Requirement Of Contingent Convertible Senior Notes	100.00%
Convertible Notes Payable [Member]
Long-Term Debt Instrument [Line Items]
Credit Facility Commitment Period	10 years
Revolving Credit Facility [Member]
Long-Term Debt Instrument [Line Items]
Long-term Debt, Gross	0
Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount	(203)	(224)
Line of Credit [Member] | Revolving Credit Facility [Member]
Long-Term Debt Instrument [Line Items]
Long-term Debt, Gross	0	0
Debt Instrument, Redemption, Period One [Member] | Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Credit Facility Commitment Period	5 years
Debt Instrument, Redemption, Period Two [Member] | Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Credit Facility Commitment Period	10 years
Debt Instrument, Redemption, Period Three [Member] | Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Credit Facility Commitment Period	15 years
Debt Instrument, Redemption, Period Four [Member] | Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Credit Facility Commitment Period	20 years
Interest Rate Contract [Member]
Long-Term Debt Instrument [Line Items]
Long-term Debt, Gross	9	10
3.25% Senior Notes due 2016 [Member]
Long-Term Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.25%
3.25% Senior Notes due 2016 [Member] | Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Long-term Debt, Gross	500	500
Debt Instrument, Interest Rate, Stated Percentage	3.25%
6.25% Euro-Denominated Senior Notes Due 2017 [ Member] | Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Long-term Debt, Gross	369	416	344
6.25% Euro-Denominated Senior Notes Due 2017 [ Member] | Cross Currency Interest Rate Contract [Member] | Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Long-term Debt, Gross	369
Derivative, Forward Exchange Rate	1.0731	1.2098	1.3325
Debt Instrument, Interest Rate, Stated Percentage	6.25%
6.5% Senior Notes Due 2017 [Member] | Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Long-term Debt, Gross	660	660
Debt Instrument, Interest Rate, Stated Percentage	6.50%
7.25% Senior Notes Due 2018 [Member] | Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Long-term Debt, Gross	669	669
Debt Instrument, Interest Rate, Stated Percentage	7.25%
Floating Rate Senior Notes due 2019 [Member] | Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Long-term Debt, Gross	1,500	1,500
6.625% Senior Notes Due 2020 [Member] | Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Long-term Debt, Gross	1,300	1,300
Debt Instrument, Interest Rate, Stated Percentage	6.625%
6.875% Senior Notes Due 2020 [Member] | Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Long-term Debt, Gross	500	500
Debt Instrument, Interest Rate, Stated Percentage	6.875%
6.125% Senior Notes Due 2021 [Member] | Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Long-term Debt, Gross	1,000	1,000
Debt Instrument, Interest Rate, Stated Percentage	6.125%
5.375% Senior Notes due 2021 [Member] | Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Long-term Debt, Gross	700	700
Debt Instrument, Interest Rate, Stated Percentage	5.375%
4.875% Senior Notes due 2022 [Member] | Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Long-term Debt, Gross	1,500	1,500
Debt Instrument, Interest Rate, Stated Percentage	4.875%
5.75% Senior Notes due 2023 [Member] | Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Long-term Debt, Gross	1,100	1,100
Debt Instrument, Interest Rate, Stated Percentage	5.75%
2.75% Contingent Convertible Senior Notes Due 2035 [Member]
Long-Term Debt Instrument [Line Items]
Common Stock Price Conversion Thresholds	$ 45.14
Debt Instrument, Date of First Required Payment	May 14, 2016
Debt Instrument, Interest Rate, Stated Percentage	2.75%
2.75% Contingent Convertible Senior Notes Due 2035 [Member] | Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Long-term Debt, Gross	396	396
Debt Instrument, Unamortized Discount	(11)	(15)
Debt Instrument, Interest Rate, Stated Percentage	2.75%
2.5% Contingent Convertible Senior Notes due 2037 [Member]
Long-Term Debt Instrument [Line Items]
Common Stock Price Conversion Thresholds	$ 59.71
Debt Instrument, Date of First Required Payment	Nov. 14, 2017
2.5% Contingent Convertible Senior Notes due 2037 [Member] | Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Long-term Debt, Gross	1,168	1,168
Debt Instrument, Interest Rate, Stated Percentage	2.50%
2.25% Contingent Convertible Senior Notes Due 2038 [Member]
Long-Term Debt Instrument [Line Items]
Common Stock Price Conversion Thresholds	$ 100.35
Debt Instrument, Date of First Required Payment	Jun. 14, 2019
2.25% Contingent Convertible Senior Notes Due 2038 [Member] | Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Long-term Debt, Gross	$ 347	$ 347
Debt Instrument, Interest Rate, Stated Percentage	2.25%