Subsequent Event (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended			3 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Jul. 17, 2012 United Kingdom Change in Corporate Income Tax Rate [Member]	Sep. 30, 2012 United Kingdom Deferred Tax Assets, Remeasurement [Member]	Jul. 17, 2012 Aggregate reduction effective April 1, 2013 United Kingdom Change in Corporate Income Tax Rate [Member]	Jul. 17, 2012 Aggregate reduction effective April 1, 2012 United Kingdom Change in Corporate Income Tax Rate [Member]
Subsequent Event [Line Items]
Reduction in Statutory Corporate Income Tax Rate					2.00%		2.00%	1.00%
Statutory Corporate Income Tax Rate					23.00%
Income tax expense (benefit)	$ 684	$ (4,049)	$ 750	$ (3,318)		$ 800

The sum of the current income tax expense or benefit and the deferred income tax expense or benefit pertaining to continuing operations.