Segment Information Schedule of consolidated revenue by geographic area (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 3,209	$ 2,794	$ 2,897	$ 2,915	$ 3,115	$ 2,737	$ 2,821	$ 2,841	$ 11,815	$ 11,514	$ 11,287
UNITED STATES [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									5,574	5,336	5,134
Americas other than U.S. [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									1,214	1,190	1,176
UNITED KINGDOM [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									1,544	1,541	1,519
Europe, Middle East and Africa [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									2,304	2,271	2,377
Asia Pacific [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									$ 1,179	$ 1,176	$ 1,081