Non-U.S. Activities - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenues	$ 10,360	$ 10,274	$ 9,864
Assets	245,192	274,119
UNITED KINGDOM
Segment Reporting Information [Line Items]
Revenues	938	1,020	903
Non-U.S.
Segment Reporting Information [Line Items]
Revenues	4,428	4,644	$ 4,299
Assets	$ 78,100	$ 60,000