Investment Securities (Investment Securities) (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Investment Holdings
Available-for-sale debt securities, fair value	$ 36,028	$ 32,830
Available-for-sale debt securities, unrealized losses	(43)	(464)
Available-for-sale debt securities, unrealized gains	1,105	166
Available-for-sale debt securities, Amortized Cost	34,966	33,128
Held-to-maturity securities, fair value	17	18
Held-to-maturity, unrealized losses	0	0
Held-to-maturity, unrealized gains	0	0
Held-to-maturity securities, amortized cost	17	18
Trading debt securities, fair value	297	287
Equity securities, fair value	564	452
U.S. Treasury and federal agencies
Investment Holdings
Available-for-sale debt securities, fair value	75	97
Available-for-sale debt securities, unrealized losses	0	(1)
Available-for-sale debt securities, unrealized gains	1	0
Available-for-sale debt securities, Amortized Cost	74	98
Obligations of states and political subdivisions
Investment Holdings
Available-for-sale debt securities, fair value	18	2
Available-for-sale debt securities, unrealized losses	0	0
Available-for-sale debt securities, unrealized gains	0	0
Available-for-sale debt securities, Amortized Cost	18	2
Held-to-maturity securities, fair value	15	16
Held-to-maturity, unrealized losses	0	0
Held-to-maturity, unrealized gains	0	0
Held-to-maturity securities, amortized cost	15	16
Asset-backed securities and other debt securities
Investment Holdings
Available-for-sale debt securities, fair value	2,206	2,015
Available-for-sale debt securities, unrealized losses	(12)	(10)
Available-for-sale debt securities, unrealized gains	29	27
Available-for-sale debt securities, Amortized Cost	2,189	1,998
Held-to-maturity securities, fair value	2	2
Held-to-maturity, unrealized losses	0	0
Held-to-maturity, unrealized gains	0	0
Held-to-maturity securities, amortized cost	2	2
Other securities
Investment Holdings
Available-for-sale debt securities, fair value	556	552
Available-for-sale debt securities, unrealized losses	0	0
Available-for-sale debt securities, unrealized gains	0	0
Available-for-sale debt securities, Amortized Cost	556	552
Residential mortgage backed securities \| Agency mortgage-backed securities
Investment Holdings
Available-for-sale debt securities, fair value	14,115	16,247
Available-for-sale debt securities, unrealized losses	(19)	(242)
Available-for-sale debt securities, unrealized gains	388	86
Available-for-sale debt securities, Amortized Cost	13,746	16,403
Commercial mortgage-backed securities \| Agency mortgage-backed securities
Investment Holdings
Available-for-sale debt securities, fair value	15,693	10,650
Available-for-sale debt securities, unrealized losses	(12)	(164)
Available-for-sale debt securities, unrealized gains	564	44
Available-for-sale debt securities, Amortized Cost	15,141	10,770
Commercial mortgage-backed securities \| Non-agency mortgage-backed securities
Investment Holdings
Available-for-sale debt securities, fair value	3,365	3,267
Available-for-sale debt securities, unrealized losses	0	(47)
Available-for-sale debt securities, unrealized gains	123	9
Available-for-sale debt securities, Amortized Cost	$ 3,242	$ 3,305

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount of investment in debt security measured at amortized cost (held-to-maturity).

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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