Stockholders' Equity - Reclassifications from AOCI (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Non-interest income	$ 172	$ 153
Non-interest income - OTTI	(8)	(15)
Interest income	5,056	4,576
Income from continuing operations before income taxes	1,470	1,663
Income tax provision (benefit)	452	529
Net income	1,013	1,153
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	21	16
Accumulated Net Unrealized Investment Gain (Loss) | Reclassification out of Accumulated Other Comprehensive Income [Member] | Securities Available for Sale
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Non-interest income	0	2
Non-interest income - OTTI	(8)	(15)
Income from continuing operations before income taxes	(8)	(13)
Income tax provision (benefit)	(3)	(5)
Net income	(5)	(8)
Accumulated Net Unrealized Investment Gain (Loss) | Reclassification out of Accumulated Other Comprehensive Income [Member] | Securities Held to Maturity
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income	(33)	(33)
Income tax provision (benefit)	(12)	(13)
Net income	(21)	(20)
Cash Flow Hedges | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income from continuing operations before income taxes	77	68
Income tax provision (benefit)	28	25
Net income	49	43
Cash Flow Hedges | Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest rate contracts
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income	79	75
Cash Flow Hedges | Reclassification out of Accumulated Other Comprehensive Income [Member] | Foreign exchange contracts
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Non-interest income	(1)	(7)
Interest income	(1)	0
Other | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income from continuing operations before income taxes	(2)	1
Income tax provision (benefit)	0	0
Net income	$ (2)	$ 1