Goodwill and Other Intangible Assets - Changes in the Carrying Amounts of Other Intangible Assets (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Servicing Asset at Fair Value, Amount		$ 1,182		$ 1,307
Intangible Assets, Net (Excluding Goodwill)		1,198	$ 1,193	1,325	$ 1,219
Amortization	[1]	(2)	(1)
Origination of Mortgage Servicing Rights (MSRs)		46	46
Servicing Assets at Fair Value, Purchased		77	56
Due to changes in inputs or assumptions	[2]	(204)	(78)
Servicing Asset at Fair Value, Other Changes in Fair Value	[3]	(43)	(48)
Servicing Asset at Fair Value, Disposals		(1)	(1)
Mortgage Servicing Rights, Fair Value [Member]
Servicing Asset at Fair Value, Amount		1,182	1,181	1,307	1,206
Amortization		0	0
Origination of Mortgage Servicing Rights (MSRs)		46	46
Servicing Assets at Fair Value, Purchased		77	56
Due to changes in inputs or assumptions	[2]	(204)	(78)
Servicing Asset at Fair Value, Other Changes in Fair Value	[3]	(43)	(48)
Servicing Asset at Fair Value, Disposals		(1)	(1)
Other Intangible Assets [Member]
Intangible Assets, Net (Excluding Goodwill)		16	12	$ 18	$ 13
Amortization	[1]	(2)	(1)
Origination of Mortgage Servicing Rights (MSRs)		0	0
Servicing Assets at Fair Value, Purchased		0	0
Due to changes in inputs or assumptions		0	0
Servicing Asset at Fair Value, Other Changes in Fair Value		0	0
Servicing Asset at Fair Value, Disposals		$ 0	$ 0

[1] Does not include expense associated with non-qualified community development investments. See Note 8, "Certain Transfers of Financial Assets and Variable Interest Entities," for additional information.

[2] Primarily reflects changes in option adjusted spreads and prepayment speed assumptions, due to changes in interest rates.

[3] Represents changes due to the collection of expected cash flows, net of accretion due to the passage of time.