Acquisition, Divestiture, and Discontinued Operations - Combined Results of Discontinued Operations (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income taxes	$ 1	$ (2)	$ 3	$ 3
Income (loss) from discontinued operations, net of taxes	1	(3)	5	5
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net interest income	6	9	20	29
Provision for credit losses	1	7	3	9
Net interest income after provision for credit losses	5	2	17	20
Noninterest income	1	(2)	4	1
Noninterest expense	4	5	13	13
Income (loss) before income taxes	2	(5)	8	8
Income taxes	1	(2)	3	3
Income (loss) from discontinued operations, net of taxes	1	(3)	5	$ 5
Charges determined by applying a matched funds transfer pricing methodology to the liabilities assumed necessary to support the discontinued operations, after tax	$ 6	$ 7	$ 18