Goodwill and Other Intangible Assets - Changes in the Carrying Amounts of Other Intangible Assets (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Servicing Asset at Fair Value, Other Changes that Affect Balance		$ 0
Finite-Lived Intangible Assets, Purchase Accounting Adjustments	[1]	(1)
Servicing Asset at Fair Value, Amount		1,645		$ 1,572
Intangible Assets, Net (Excluding Goodwill)		1,729	$ 1,198	1,657	$ 1,325
Amortization	[2]	(5)	(2)
Origination of Mortgage Servicing Rights (MSRs)		101	46
Servicing Assets at Fair Value, Purchased			77
Due to changes in inputs or assumptions	[3]	27	(204)
Servicing Asset at Fair Value, Other Changes in Fair Value	[4]	(50)	(43)
Servicing Asset at Fair Value, Disposals			(1)
Mortgage Servicing Rights, Fair Value [Member]
Servicing Asset at Fair Value, Amount		1,645	1,182	1,572	1,307
Amortization	[2]	0	0
Origination of Mortgage Servicing Rights (MSRs)		96	46
Servicing Assets at Fair Value, Purchased			77
Due to changes in inputs or assumptions	[3]	27	(204)
Servicing Asset at Fair Value, Other Changes in Fair Value	[4]	(50)	(43)
Servicing Asset at Fair Value, Disposals			(1)
Other Intangible Assets [Member]
Intangible Assets, Net (Excluding Goodwill)		84	16	85	$ 18
Amortization	[2]	(5)	(2)
Origination of Mortgage Servicing Rights (MSRs)		5	0
Servicing Assets at Fair Value, Purchased			0
Due to changes in inputs or assumptions	[3]	0	0
Servicing Asset at Fair Value, Other Changes in Fair Value	[4]	0	0
Servicing Asset at Fair Value, Disposals			$ 0
Commercial Mortgage Servicing Rights [Member]
Servicing Asset at Fair Value, Amount		$ 65		$ 62

[1] Represents measurement period adjustment on other intangible assets previously acquired in Pillar acquisition. See Note 2, "Acquisitions/Dispositions," for additional information.

[2] Does not include expense associated with non-qualified community development investments. See Note 9, "Certain Transfers of Financial Assets and Variable Interest Entities," for additional information.

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

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