Commercial Paper and Long-Term Debt (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Par Value	$ 16,789		$ 16,952
Carrying Value	16,630		16,739
Fair Value	17,899		17,596
Commercial Paper [Member]
Par Value	1,124		1,115
Commercial Paper	1,124		1,115
Debt Instrument, Fair Value Disclosure	1,124		1,115
4.750% Notes Due February 2014 [Member]
Debt Instrument, Interest Rate, Stated Percentage	4.75%
Par Value	0		172
Carrying Value	0		173
Fair Value	0		173
5.000% Notes Due August 2014 [Member]
Debt Instrument, Interest Rate, Stated Percentage	5.00%
Par Value	389		389
Carrying Value	395		397
Fair Value	396		400
Floating-rate Notes Due August 2014 [Member]
Par Value	250		250
Carrying Value	250		250
Fair Value	250		250
4.875% Notes Due March 2015 [Member]
Debt Instrument, Interest Rate, Stated Percentage	4.875%
Par Value	416	[1]	416	[1]
Carrying Value	429	[1]	431	[1]
Fair Value	433	[1]	436	[1]
0.850% Notes due October 2015 [Member]
Debt Instrument, Interest Rate, Stated Percentage	0.85%
Par Value	625	[1]	625	[1]
Carrying Value	624	[1]	624	[1]
Fair Value	628	[1]	628	[1]
5.375% Notes Due March 2016 [Member]
Debt Instrument, Interest Rate, Stated Percentage	5.375%
Par Value	601	[1]	601	[1]
Carrying Value	637	[1]	641	[1]
Fair Value	654	[1]	657	[1]
1.875% Notes Due November 2016 [Member]
Debt Instrument, Interest Rate, Stated Percentage	1.875%
Par Value	400		400
Carrying Value	398		398
Fair Value	409		408
5.360% Notes Due November 2016 [Member]
Debt Instrument, Interest Rate, Stated Percentage	5.36%
Par Value	95		95
Carrying Value	95		95
Fair Value	106		107
6.000% Notes Due June 2017 [Member]
Debt Instrument, Interest Rate, Stated Percentage	6.00%
Par Value	441		441
Carrying Value	476		479
Fair Value	502		506
1.400% Notes due October 2017 [Member]
Debt Instrument, Interest Rate, Stated Percentage	1.40%
Par Value	625	[1]	625	[1]
Carrying Value	613	[1]	613	[1]
Fair Value	623	[1]	617	[1]
6.000% Notes Due November 2017 [Member]
Debt Instrument, Interest Rate, Stated Percentage	6.00%
Par Value	156		156
Carrying Value	167		168
Fair Value	178		178
6.000% Notes Due February 2018 [Member]
Debt Instrument, Interest Rate, Stated Percentage	6.00%
Par Value	1,100		1,100
Carrying Value	1,115		1,116
Fair Value	1,266		1,271
1.625% Notes Due March 2019 [Member]
Debt Instrument, Interest Rate, Stated Percentage	1.625%
Par Value	500	[1]	500	[1]
Carrying Value	491	[1]	489	[1]
Fair Value	486	[1]	481	[1]
3.875% Notes Due October 2020 [Member]
Debt Instrument, Interest Rate, Stated Percentage	3.875%
Par Value	450	[1]	450	[1]
Carrying Value	441	[1]	435	[1]
Fair Value	476	[1]	474	[1]
4.700% Notes Due February 2021 [Member]
Debt Instrument, Interest Rate, Stated Percentage	4.70%
Par Value	400		400
Carrying Value	415		416
Fair Value	441		436
3.375% Notes Due November 2021 [Member]
Debt Instrument, Interest Rate, Stated Percentage	3.375%
Par Value	500	[1]	500	[1]
Carrying Value	480	[1]	472	[1]
Fair Value	507	[1]	494	[1]
2.875% Notes Due March 2022 [Member]
Debt Instrument, Interest Rate, Stated Percentage	2.875%
Par Value	1,100	[1]	1,100	[1]
Carrying Value	1,001	[1]	981	[1]
Fair Value	1,069	[1]	1,046	[1]
0.000% Notes Due November 2022 [Member]
Debt Instrument, Interest Rate, Stated Percentage	0.00%
Par Value	15		15
Carrying Value	10		9
Fair Value	11		10
2.750% Notes due February 2023 [Member]
Debt Instrument, Interest Rate, Stated Percentage	2.75%
Par Value	625	[1]	625	[1]
Carrying Value	577	[1]	563	[1]
Fair Value	588	[1]	572	[1]
2.875% Notes due March 2023 [Member]
Debt Instrument, Interest Rate, Stated Percentage	2.875%
Par Value	750	[1]	750	[1]
Carrying Value	745	[1]	729	[1]
Fair Value	711	[1]	698	[1]
5.800% Notes Due March 2036 [Member]
Debt Instrument, Interest Rate, Stated Percentage	5.80%
Par Value	850		850
Carrying Value	845		845
Fair Value	989		935
6.500% Notes Due June 2037 [Member]
Debt Instrument, Interest Rate, Stated Percentage	6.50%
Par Value	500		500
Carrying Value	495		495
Fair Value	628		593
6.625% Notes Due November 2037 [Member]
Debt Instrument, Interest Rate, Stated Percentage	6.625%
Par Value	650		650
Carrying Value	646		645
Fair Value	837		786
6.875% Notes Due February 2038 [Member]
Debt Instrument, Interest Rate, Stated Percentage	6.875%
Par Value	1,100		1,100
Carrying Value	1,085		1,084
Fair Value	1,447		1,370
5.700% Notes Due October 2040 [Member]
Debt Instrument, Interest Rate, Stated Percentage	5.70%
Par Value	300		300
Carrying Value	298		298
Fair Value	350		329
5.950% Notes Due February 2041 [Member]
Debt Instrument, Interest Rate, Stated Percentage	5.95%
Par Value	350		350
Carrying Value	348		348
Fair Value	419		397
4.625% Notes Due November 2041 [Member]
Debt Instrument, Interest Rate, Stated Percentage	4.625%
Par Value	600		600
Carrying Value	593		593
Fair Value	603		567
4.375% Notes Due March 2042 [Member]
Debt Instrument, Interest Rate, Stated Percentage	4.375%
Par Value	502		502
Carrying Value	486		486
Fair Value	488		459
3.950% Notes due October 2042 [Member]
Debt Instrument, Interest Rate, Stated Percentage	3.95%
Par Value	625		625
Carrying Value	611		611
Fair Value	566		530
4.250% Notes due March 2043 [Member]
Debt Instrument, Interest Rate, Stated Percentage	4.25%
Par Value	750		750
Carrying Value	740		740
Fair Value	$ 714		$ 673

[1] (a)Fixed-rate debt instruments hedged with interest rate swap contracts. See below for more information on the Company’s interest rate swaps.