Segment and Related Information (Geographic Data) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues from external customers	$ 12,286	$ 12,737	$ 8,521
Long-lived assets	30,727	28,125
US [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues from external customers	9,950	11,084	7,760
Long-lived assets	20,776	19,129
UK [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues from external customers	2,336	1,653	761
Long-lived assets	$ 9,951	$ 8,996