Quarterly Financial Data (Unaudited) Quarterly Financial Data (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Total revenues	$ 25,916	$ 25,280	$ 25,234	$ 25,432	$ 24,030	$ 23,668	$ 23,264	$ 23,193	$ 101,862	$ 94,155	$ 87,138
Total operating costs	23,842	23,210	23,135	23,211	22,228	21,523	21,363	21,177	93,398	86,291	80,779
Earnings from operations	2,074	2,070	2,099	2,221	1,802	2,145	1,901	2,016	8,464	7,864	6,359
Net earnings	$ 1,258	$ 1,271	$ 1,267	$ 1,346	$ 1,043	$ 1,277	$ 1,123	$ 1,191	$ 5,142	$ 4,634	$ 3,822
Basic net earnings per common share	$ 1.19	$ 1.19	$ 1.18	$ 1.24	$ 0.95	$ 1.15	$ 1.00	$ 1.04	$ 4.81	$ 4.14	$ 3.27
Diluted net earnings per common share	$ 1.17	$ 1.17	$ 1.16	$ 1.22	$ 0.94	$ 1.14	$ 0.99	$ 1.03	$ 4.73	$ 4.10	$ 3.24