Goodwill - Additional Information (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended					3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jul. 31, 2013	Dec. 31, 2013 Excluding GBM [Member]	Dec. 31, 2013 Gbm [Member]
Goodwill [Line Items]
Goodwill	$ 1,612	$ 2,228	$ 2,228
Goodwill accumulated impairment losses	670	54
Carrying value as a percent of fair value				92.00%	80.00%
Goodwill impairment (Note 11)	$ 616	$ 0	$ 0			$ 616