Debt - Short-term and Long-term Debt (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Debt Disclosure [Abstract]
Commercial paper	$ 100		$ 100
Current maturities of long-term debt	21		41
Other	0		92
Total short-term debt	121		233
Debt Instrument [Line Items]
Long-term debt	5,024		5,014
Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt	5,024		5,014
Notes due 2016 2.75% Interest [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt	600		600
Stated interest rate	2.75%		2.75%
Notes due 2017 5.375% Interest [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt	250		250
Stated interest rate	5.375%		5.375%
Notes due 2018 6.35% Interest [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt	131		131
Stated interest rate	6.35%		6.35%
Notes due 2019 8.5% Interest [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt	251		251
Stated interest rate	8.50%		8.50%
Notes due 2020 4.375% Interest [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt	250	[1]	249	[1]
Stated interest rate	4.375%		4.375%
Notes due 2020 5.125% Interest [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt	300	[1]	299	[1]
Stated interest rate	5.125%		5.125%
Notes due 2021 6.37% Interest [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt	78		78
Stated interest rate	6.37%		6.37%
Notes Due 2021 4.5% Interest [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt	298	[1]	299	[1]
Stated interest rate	4.50%		4.50%
Notes due 2022 4% Interest [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt	745		744
Stated interest rate	4.00%		4.00%
Notes due 2023 7.65% Interest [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt	100		100
Stated interest rate	7.65%		7.65%
Notes due 2023 8.3% Interest [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt	17		17
Stated interest rate	8.30%		8.30%
Debentures due 2027 7.875% Interest [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt	300		300
Stated interest rate	7.875%		7.875%
Step Down Notes Due 2033 8.3% Interest [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt	83		83
Stated interest rate	8.30%		8.30%
Notes due 2036 6.15% Interest [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt	500		500
Stated interest rate	6.15%		6.15%
Notes Due 2041 5.875% Interest [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt	298		298
Stated interest rate	5.875%		5.875%
Notes due 2042 5.375% Interest [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt	750		750
Stated interest rate	5.375%		5.375%
Other Long Term Debt [Member] | Uncollateralized Debt [Member]
Debt Instrument [Line Items]
Long-term debt	$ 73		$ 65

[1] In 2014, the Company entered into interest rate swap contracts hedging a portion of these fixed-rate debt instruments. See Note 9 for further information about the Company’s interest rate risk management and these derivative instruments.