Fair Value Option Elected, Difference Between the Aggregate Fair Value and the Aggregate Unpaid Principal Balance (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Loans Held-for-sale, Fair Value Disclosure	$ 2,672	[1]	$ 3,243	[1]
Aggregate Fair Value Under Fair Value Option
Trading Account Assets, Fair Value Disclosure	2,200		2,319
Loans Held-for-sale, Fair Value Disclosure	2,661		3,237
Loans, Held for Investment, Fair Value Disclosure	344		360
Brokered deposits	810		832
Long-term debt	1,632		1,622
Aggregate Fair Value Under Fair Value Option | Loans Held-for-Sale
Past due loans of 90 days or more	2		3
Nonaccrual loans	9		3
Aggregate Fair Value Under Fair Value Option | Loans Held For Investment [Member]
Past due loans of 90 days or more	2		1
Nonaccrual loans	14		18
Aggregate Unpaid Principal Balance Under Fair Value Option
Trading Account Assets, Fair Value Disclosure	2,160		2,285
Loans Held-for-sale, Fair Value Disclosure	2,591		3,109
Loans, Held for Investment, Fair Value Disclosure	357		371
Brokered deposits	803		825
Long-term debt	1,461		1,462
Aggregate Unpaid Principal Balance Under Fair Value Option | Loans Held-for-Sale
Past due loans of 90 days or more	2		5
Nonaccrual loans	12		12
Aggregate Unpaid Principal Balance Under Fair Value Option | Loans Held For Investment [Member]
Past due loans of 90 days or more	3		3
Nonaccrual loans	23		28
Fair Value Over/(Under) Unpaid Principal
Trading Account Assets, Fair Value Disclosure	40		34
Loans Held-for-sale, Fair Value Disclosure	70		128
Loans, Held for Investment, Fair Value Disclosure	(13)		(11)
Brokered deposits	7		7
Long-term debt	171		160
Fair Value Over/(Under) Unpaid Principal | Loans Held-for-Sale
Past due loans of 90 days or more	0		(2)
Nonaccrual loans	(3)		(9)
Fair Value Over/(Under) Unpaid Principal | Loans Held For Investment [Member]
Past due loans of 90 days or more	(1)		(2)
Nonaccrual loans	$ (9)		$ (10)

[1] 1 Includes loans held for sale, at fair value, of consolidated VIEs315 319