Securities Available for Sale (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Dec. 31, 2012		Dec. 31, 2013		Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Document Period End Date	Dec. 31, 2012		Dec. 31, 2013
Amortized Cost	$ 21,087		$ 22,622		$ 21,087
Unrealized Gains			454		880
Unrealized Losses			534		14
Available-for-sale Securities	21,953		22,542		21,953
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	212		1,334		212
Unrealized Gains			6		10
Unrealized Losses			47		0
Available-for-sale Securities	222		1,293		222
US Government Agencies Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,987		1,028		1,987
Unrealized Gains			13		85
Unrealized Losses			57		3
Available-for-sale Securities	2,069		984		2,069
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	310		232		310
Unrealized Gains			7		15
Unrealized Losses			2		5
Available-for-sale Securities	320		237		320
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	17,416		18,915		17,416
Unrealized Gains			421		756
Unrealized Losses			425		3
Available-for-sale Securities	18,169		18,911		18,169
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	205		155		205
Unrealized Gains			1		4
Unrealized Losses			2		0
Available-for-sale Securities	209		154		209
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	214		78		214
Unrealized Gains			2		5
Unrealized Losses			1		3
Available-for-sale Securities	216		79		216
Other Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	42		39		42
Unrealized Gains			3		4
Unrealized Losses			0		0
Available-for-sale Securities	46		42		46
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	701	[1]	841	[1]	701	[1]
Unrealized Gains			1	[1]	1	[1]
Unrealized Losses			0	[1]	0	[1]
Available-for-sale Securities	$ 702	[1]	$ 842	[1]	$ 702	[1]

[1] At December 31, 2013, other equity securities was comprised of the following: $336 million in FHLB of Atlanta stock, $402 million in Federal Reserve Bank stock, $103 million in mutual fund investments, and $1 million of other. At December 31, 2012, other equity securities was comprised of the following: $229 million in FHLB of Atlanta stock, $402 million in Federal Reserve Bank stock, $69 million in mutual fund investments, and $2 million of other.