Fair Value Measurements - Changes in Fair Value of Level 3 Assets and Liabilities (Detail) - Level 3 [Member] - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance		$ 2,207	$ 3,356
Fair Value Assets, Gains (Losses) Included In Earnings		(133)	133
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income		(4)	0
Fair Value Assets, Purchases		0	0
Fair Value Assets, Issuances		0	(35)
Fair Value Assets, Settlements		(109)	(1,252)
Fair Value Assets, Transfers Into Level 3		106	4
Fair Value Assets, Transfers Out of Level 3		21	1
Fair Value Assets, Ending Balance		2,088	2,207
Fair Value Assets, Current Period Unrealized Gains (Losses)		(132)	85
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance		(1,538)	(1,906)
Fair Value Liability, Gains (Losses) Included In Earnings		83	(133)
Fair Value, Liability, Gains (Losses) Included in Other Comprehensive Income		23	0
Fair Value Liability, Purchases		0	0
Fair Value Liability, Issuances		(597)	(499)
Fair Value Liability, Settlements		356	681
Fair Value Liability, Transfers Into Level 3		(29)	(43)
Fair Value Liability, Transfers Out of Level 3		365	362
Fair Value Liability, Ending Balance		(1,337)	(1,538)
Fair Value Liability, Current Period Unrealized Gains (Losses)		76	(99)
Interest rate contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]	0	1
Fair Value Assets, Gains (Losses) Included In Earnings	[1]	2	(1)
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[1]	0	0
Fair Value Assets, Purchases	[1]	0	0
Fair Value Assets, Issuances	[1]	0	0
Fair Value Assets, Settlements	[1]	0	0
Fair Value Assets, Transfers Into Level 3	[1]	0	0
Fair Value Assets, Transfers Out of Level 3	[1]	0	0
Fair Value Assets, Ending Balance	[1]	2	0
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	2	(1)
Foreign exchange contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]	0	0
Fair Value Assets, Gains (Losses) Included In Earnings	[1]	(2)	0
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[1]	0	0
Fair Value Assets, Purchases	[1]	0	0
Fair Value Assets, Issuances	[1]	0	0
Fair Value Assets, Settlements	[1]	1	0
Fair Value Assets, Transfers Into Level 3	[1]	0	0
Fair Value Assets, Transfers Out of Level 3	[1]	0	0
Fair Value Assets, Ending Balance	[1]	(1)	0
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	(1)	0
Equity contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]	81	(2)
Fair Value Assets, Gains (Losses) Included In Earnings	[1]	(126)	102
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[1]	0	0
Fair Value Assets, Purchases	[1]	0	0
Fair Value Assets, Issuances	[1]	0	0
Fair Value Assets, Settlements	[1]	(26)	(24)
Fair Value Assets, Transfers Into Level 3	[1]	(2)	4
Fair Value Assets, Transfers Out of Level 3	[1]	21	1
Fair Value Assets, Ending Balance	[1]	(52)	81
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	(95)	68
Credit contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1]	114	193
Fair Value Assets, Gains (Losses) Included In Earnings	[1]	(2)	(7)
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[1]	0	0
Fair Value Assets, Purchases	[1]	0	0
Fair Value Assets, Issuances	[1]	0	0
Fair Value Assets, Settlements	[1]	(60)	(72)
Fair Value Assets, Transfers Into Level 3	[1]	0	0
Fair Value Assets, Transfers Out of Level 3	[1]	0	0
Fair Value Assets, Ending Balance	[1]	52	114
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1]	(44)	(16)
Other Contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[1],[2]	(46)	(9)
Fair Value Assets, Gains (Losses) Included In Earnings	[1],[2]	(15)	(10)
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[1],[2]	0	0
Fair Value Assets, Purchases	[1],[2]	0	0
Fair Value Assets, Issuances	[1],[2]	0	(35)
Fair Value Assets, Settlements	[1],[2]	26	8
Fair Value Assets, Transfers Into Level 3	[1],[2]	0	0
Fair Value Assets, Transfers Out of Level 3	[1],[2]	0	0
Fair Value Assets, Ending Balance	[1],[2]	(35)	(46)
Fair Value Assets, Current Period Unrealized Gains (Losses)	[1],[2]	0	0
Domestic Deposits [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance	[3]	(897)	(1,407)
Fair Value Liability, Gains (Losses) Included In Earnings	[3]	32	(48)
Fair Value, Liability, Gains (Losses) Included in Other Comprehensive Income	[3]	13	7
Fair Value Liability, Purchases	[3]	0	0
Fair Value Liability, Issuances	[3]	(400)	(204)
Fair Value Liability, Settlements	[3]	149	526
Fair Value Liability, Transfers Into Level 3	[3]	(28)	(31)
Fair Value Liability, Transfers Out of Level 3	[3]	206	260
Fair Value Liability, Ending Balance	[3]	(925)	(897)
Fair Value Liability, Current Period Unrealized Gains (Losses)	[3]	33	(28)
Long-term debt [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Liability, Beginning Balance	[3]	(641)	(499)
Fair Value Liability, Gains (Losses) Included In Earnings	[3]	51	(85)
Fair Value, Liability, Gains (Losses) Included in Other Comprehensive Income	[3]	10	(7)
Fair Value Liability, Purchases	[3]	0	0
Fair Value Liability, Issuances	[3]	(197)	(295)
Fair Value Liability, Settlements	[3]	207	155
Fair Value Liability, Transfers Into Level 3	[3]	(1)	(12)
Fair Value Liability, Transfers Out of Level 3	[3]	159	102
Fair Value Liability, Ending Balance	[3]	(412)	(641)
Fair Value Liability, Current Period Unrealized Gains (Losses)	[3]	43	(71)
Trading assets, excluding derivatives [Member] | Collateralized debt obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[4]	129	184
Fair Value Assets, Gains (Losses) Included In Earnings	[4]	13	28
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[4]	0	0
Fair Value Assets, Purchases	[4]	0	0
Fair Value Assets, Issuances	[4]	0	0
Fair Value Assets, Settlements	[4]	(42)	(83)
Fair Value Assets, Transfers Into Level 3	[4]	0	0
Fair Value Assets, Transfers Out of Level 3	[4]	0	0
Fair Value Assets, Ending Balance	[4]	100	129
Fair Value Assets, Current Period Unrealized Gains (Losses)	[4]	10	13
Trading assets, excluding derivatives [Member] | Residential mortgage asset-backed securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[4]	0
Fair Value Assets, Gains (Losses) Included In Earnings	[4]	0
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[4]	0
Fair Value Assets, Purchases	[4]	0
Fair Value Assets, Issuances	[4]	0
Fair Value Assets, Settlements	[4]	0
Fair Value Assets, Transfers Into Level 3		16
Fair Value Assets, Transfers Out of Level 3	[4]	0
Fair Value Assets, Ending Balance	[4]	16	0
Fair Value Assets, Current Period Unrealized Gains (Losses)	[4]	0
Trading assets, excluding derivatives [Member] | Student loan asset-backed securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance		0
Fair Value Assets, Gains (Losses) Included In Earnings	[4]	0
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income		0
Fair Value Assets, Purchases		0
Fair Value Assets, Issuances		0
Fair Value Assets, Settlements		0
Fair Value Assets, Transfers Into Level 3		92
Fair Value Assets, Transfers Out of Level 3		0
Fair Value Assets, Ending Balance		92	0
Fair Value Assets, Current Period Unrealized Gains (Losses)		0
Trading assets, excluding derivatives [Member] | Corporate and other domestic debt securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[4]	1,803	2,884
Fair Value Assets, Gains (Losses) Included In Earnings	[4]	0	0
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income		0	0	[4]
Fair Value Assets, Purchases		0	0	[4]
Fair Value Assets, Issuances		0	0	[4]
Fair Value Assets, Settlements		0	(1,081)	[4]
Fair Value Assets, Transfers Into Level 3		0	0	[4]
Fair Value Assets, Transfers Out of Level 3		0	0	[4]
Fair Value Assets, Ending Balance		1,803	1,803	[4]
Fair Value Assets, Current Period Unrealized Gains (Losses)		0	0	[4]
Available-for-sale securities [Member] | Other asset-backed securities available-for-sale [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[5]	111	105
Fair Value Assets, Gains (Losses) Included In Earnings	[5]	0	6
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[5]	(4)	0
Fair Value Assets, Purchases	[5]	0	0
Fair Value Assets, Issuances	[5]	0	0
Fair Value Assets, Settlements	[5]	0	0
Fair Value Assets, Transfers Into Level 3	[5]	0	0
Fair Value Assets, Transfers Out of Level 3	[5]	0	0
Fair Value Assets, Ending Balance	[5]	107	111
Fair Value Assets, Current Period Unrealized Gains (Losses)	[5]	(4)	6
Other assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Assets, Beginning Balance	[6]	15	0
Fair Value Assets, Gains (Losses) Included In Earnings	[6]	(3)	15
Fair Value Assets, Gains (Losses) Included in Other Comprehensive Income	[6]	0	0
Fair Value Assets, Purchases	[6]	0	0
Fair Value Assets, Issuances	[6]	0	0
Fair Value Assets, Settlements	[6]	(8)	0
Fair Value Assets, Transfers Into Level 3	[6]	0	0
Fair Value Assets, Transfers Out of Level 3	[6]	0	0
Fair Value Assets, Ending Balance	[6]	4	15
Fair Value Assets, Current Period Unrealized Gains (Losses)	[6]	$ 0	$ 15

[1] Level 3 net derivatives included derivative assets of $179 million and derivative liabilities of $213 million at December 31, 2018 and derivative assets of $301 million and derivative liabilities of $152 million at December 31, 2017. Gains (losses) on derivatives, net are predominantly included in trading revenue in the consolidated statement of income (loss).

[2] Consists of swap agreements entered into in conjunction with the sales of Visa Class B Shares.

[3] Excluding unrealized gains (losses) on fair value option liabilities attributable to our own credit spread, which are recorded in other comprehensive income (loss), gains (losses) on fair value option liabilities are included in gain (loss) on instruments designated at fair value and related derivatives in the consolidated statement of income (loss).

[4] Gains (losses) on trading assets, excluding derivatives are included in trading revenue in the consolidated statement of income (loss).

[5] Realized gains (losses) on securities available-for-sale are included in other securities gains, net in the consolidated statement of income (loss). Unrealized gains (losses) on securities available-for-sale are included in other comprehensive income (loss).

[6] Represents contingent consideration receivable associated with the sale of a portion of our Private Banking business. Gains (losses) associated with this transaction are included in other income (loss) in the consolidated statement of income (loss).