Geographic Information (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Geographic Information [Line Items]
Revenues	$ 144,077	$ 146,917	$ 133,559
Long-Lived Assets	51,644	46,216	38,830
UNITED STATES
Geographic Information [Line Items]
Revenues	82,665	85,459	76,055
Long-Lived Assets	33,213	28,276	22,986
United Kingdom
Geographic Information [Line Items]
Revenues	11,742	10,038	9,208
Long-Lived Assets	1,491	1,503	1,668
Canada
Geographic Information [Line Items]
Revenues	9,409	9,729	9,470
Long-Lived Assets	3,919	3,154	2,580
Germany
Geographic Information [Line Items]
Revenues	7,487	8,600	8,005
Long-Lived Assets	2,510	2,635	2,719
MEXICO
Geographic Information [Line Items]
Revenues	1,757	1,992	1,818
Long-Lived Assets	1,748	1,910	1,990
All Other
Geographic Information [Line Items]
Revenues	31,017	31,099	29,003
Long-Lived Assets	$ 8,763	$ 8,738	$ 6,887