Available-for-Sale and Held-to-Maturity Securities (Detail) - USD ($) $ in Millions		Jun. 30, 2015		Dec. 31, 2014
Investment Holdings [Line Items]
Available-for-sale securities, fair value	[1]	$ 27,987		$ 22,408
Available-for-sale securities, unrealized losses		(76)		(5)
Available-for-sale securities, unrealized gains		580		736
Available-for-sale and other securities, Amortized Cost		27,483		21,677
Held-to-maturity securities, fair value		157		187
Held-to-maturity securities, amortized cost	[2]	157		187
U.S. Treasury and federal agencies
Investment Holdings [Line Items]
Available-for-sale securities, fair value		1,615		1,632
Available-for-sale securities, unrealized gains		71		87
Available-for-sale and other securities, Amortized Cost		1,544		1,545
Obligations of states and political subdivisions
Investment Holdings [Line Items]
Available-for-sale securities, fair value		177		192
Available-for-sale securities, unrealized gains		5		7
Available-for-sale and other securities, Amortized Cost		172		185
Held-to-maturity securities, fair value		156		186
Held-to-maturity securities, amortized cost		156		186
Agency mortgage-backed securities | Residential mortgage backed securities
Investment Holdings [Line Items]
Available-for-sale securities, fair value		15,954	[3]	12,404	[4]
Available-for-sale securities, unrealized losses		(32)	[3]	(1)	[4]
Available-for-sale securities, unrealized gains		333	[3]	437	[4]
Available-for-sale and other securities, Amortized Cost		15,653	[3]	11,968	[4]
Agency mortgage-backed securities | Commercial mortgage backed securities
Investment Holdings [Line Items]
Available-for-sale securities, fair value		5,751		4,565
Available-for-sale securities, unrealized losses		(18)		(1)
Available-for-sale securities, unrealized gains		82		101
Available-for-sale and other securities, Amortized Cost		5,687		4,465
Non-agency mortgage-backed securities | Commercial mortgage backed securities
Investment Holdings [Line Items]
Available-for-sale securities, fair value		2,414		1,550
Available-for-sale securities, unrealized losses		(19)
Available-for-sale securities, unrealized gains		51		61
Available-for-sale and other securities, Amortized Cost		2,382		1,489
Asset-backed securities and other debt securities
Investment Holdings [Line Items]
Available-for-sale securities, fair value		1,374		1,362
Available-for-sale securities, unrealized losses		(6)		(2)
Available-for-sale securities, unrealized gains		36		40
Available-for-sale and other securities, Amortized Cost		1,344		1,324
Held-to-maturity securities, fair value		1		1
Held-to-maturity securities, amortized cost		1		1
Equity securities
Investment Holdings [Line Items]
Available-for-sale securities, fair value		702	[5]	703	[6]
Available-for-sale securities, unrealized losses		(1)	[5]	(1)	[6]
Available-for-sale securities, unrealized gains		2	[5]	3	[6]
Available-for-sale and other securities, Amortized Cost		$ 701	[5]	$ 701	[6]

[1] Amortized cost of $27,483 and $21,677 at June 30, 2015 and December 31, 2014, respectively.

[2] Fair value of $157 and $187 at June 30, 2015 and December 31, 2014, respectively.

[3] Includes interest-only mortgage-backed securities of $162 as of June 30, 2015 recorded at fair value with fair value changes recorded in securities gains, net, in the Condensed Consolidated Statements of Income.

[4] Includes interest-only mortgage-backed securities of $175 as of December 31, 2014, recorded at fair value with fair value changes recorded in securities gains, net, in the Condensed Consolidated Statements of Income.

[5] Equity securities consist of FHLB and FRB restricted stock holdings of $248 and $353, respectively, at June 30, 2015, that are carried at cost, and certain mutual fund and equity security holdings.

[6] Equity securities consist of FHLB and FRB restricted stock holdings of $248 and $352, respectively, at December 31, 2014, that are carried at cost, and certain mutual fund and equity security holdings