Fair Values of Assets and Liabilities (Fair Value Hierarchy for Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions		Jun. 30, 2023	Dec. 31, 2022
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	[1]	$ 125,769	$ 147,871
Certificates of deposit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		348	2,231
U.S. agency mortgage-backed securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		71,727	77,688
U.S. Treasury securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		28,524	40,002
Asset-backed securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		10,957	13,023
Corporate debt securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		12,282	12,555
Foreign government agency securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		978	969
U.S. state and municipal securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		572	638
Non-agency commercial mortgage-backed securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		263	450
Other [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		118	315
Fair Value, Recurring [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:		14,361	14,055
Investments segregated and on deposit for regulatory purposes:		15,328	24,645
Fair Value		125,769	147,871
Other assets:		1,668	1,432
Total assets		157,126	188,003
Total accrued expenses and other liabilities		1,474	1,261
Total liabilities		1,474	1,261
Fair Value, Recurring [Member] | Money market funds [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:		14,361	14,007
Fair Value, Recurring [Member] | Commercial paper [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:			48
Fair Value, Recurring [Member] | U.S. Government securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Investments segregated and on deposit for regulatory purposes:		14,230	23,645
Other assets:		2	1
Fair Value, Recurring [Member] | Certificates of deposit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Investments segregated and on deposit for regulatory purposes:		1,098	1,000
Fair Value		348	2,231
Fair Value, Recurring [Member] | U.S. agency mortgage-backed securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		71,727	77,688
Fair Value, Recurring [Member] | U.S. Treasury securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		28,524	40,002
Fair Value, Recurring [Member] | Asset-backed securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		10,957	13,023
Fair Value, Recurring [Member] | Corporate debt securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		12,282	12,555
Fair Value, Recurring [Member] | Foreign government agency securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		978	969
Fair Value, Recurring [Member] | U.S. state and municipal securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		572	638
Fair Value, Recurring [Member] | Non-agency commercial mortgage-backed securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		263	450
Fair Value, Recurring [Member] | Other [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		118	315
Fair Value, Recurring [Member] | Total other securities owned at fair value [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		1,667	1,432
Fair Value, Recurring [Member] | Equity, corporate debt, and other securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		947	810
Fair Value, Recurring [Member] | Mutual Funds And Exchange Traded Funds (ETFs) [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		695	596
Fair Value, Recurring [Member] | State and municipal debt obligations [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		23	25
Fair Value, Recurring [Member] | Interest Rate Swaps [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		1
Fair Value, Recurring [Member] | Other [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Total accrued expenses and other liabilities		1,474	1,261
Fair Value, Recurring [Member] | Level 1 [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:		14,361	14,007
Investments segregated and on deposit for regulatory purposes:		0	0
Fair Value		0	0
Other assets:		1,575	1,351
Total assets		15,936	15,358
Total accrued expenses and other liabilities		1,428	1,218
Total liabilities		1,428	1,218
Fair Value, Recurring [Member] | Level 1 [Member] | Money market funds [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:		14,361	14,007
Fair Value, Recurring [Member] | Level 1 [Member] | Commercial paper [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:			0
Fair Value, Recurring [Member] | Level 1 [Member] | U.S. Government securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Investments segregated and on deposit for regulatory purposes:		0	0
Other assets:		0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Certificates of deposit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Investments segregated and on deposit for regulatory purposes:		0	0
Fair Value		0	0
Fair Value, Recurring [Member] | Level 1 [Member] | U.S. agency mortgage-backed securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		0	0
Fair Value, Recurring [Member] | Level 1 [Member] | U.S. Treasury securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Asset-backed securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Corporate debt securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Foreign government agency securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		0	0
Fair Value, Recurring [Member] | Level 1 [Member] | U.S. state and municipal securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Non-agency commercial mortgage-backed securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Other [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Total other securities owned at fair value [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		1,575	1,351
Fair Value, Recurring [Member] | Level 1 [Member] | Equity, corporate debt, and other securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		880	755
Fair Value, Recurring [Member] | Level 1 [Member] | Mutual Funds And Exchange Traded Funds (ETFs) [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		695	596
Fair Value, Recurring [Member] | Level 1 [Member] | State and municipal debt obligations [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Interest Rate Swaps [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		0
Fair Value, Recurring [Member] | Level 1 [Member] | Other [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Total accrued expenses and other liabilities		1,428	1,218
Fair Value, Recurring [Member] | Level 2 [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:		0	48
Investments segregated and on deposit for regulatory purposes:		15,328	24,645
Fair Value		125,769	147,871
Other assets:		93	81
Total assets		141,190	172,645
Total accrued expenses and other liabilities		46	43
Total liabilities		46	43
Fair Value, Recurring [Member] | Level 2 [Member] | Money market funds [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:		0	0
Fair Value, Recurring [Member] | Level 2 [Member] | Commercial paper [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:			48
Fair Value, Recurring [Member] | Level 2 [Member] | U.S. Government securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Investments segregated and on deposit for regulatory purposes:		14,230	23,645
Other assets:		2	1
Fair Value, Recurring [Member] | Level 2 [Member] | Certificates of deposit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Investments segregated and on deposit for regulatory purposes:		1,098	1,000
Fair Value		348	2,231
Fair Value, Recurring [Member] | Level 2 [Member] | U.S. agency mortgage-backed securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		71,727	77,688
Fair Value, Recurring [Member] | Level 2 [Member] | U.S. Treasury securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		28,524	40,002
Fair Value, Recurring [Member] | Level 2 [Member] | Asset-backed securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		10,957	13,023
Fair Value, Recurring [Member] | Level 2 [Member] | Corporate debt securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		12,282	12,555
Fair Value, Recurring [Member] | Level 2 [Member] | Foreign government agency securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		978	969
Fair Value, Recurring [Member] | Level 2 [Member] | U.S. state and municipal securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		572	638
Fair Value, Recurring [Member] | Level 2 [Member] | Non-agency commercial mortgage-backed securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		263	450
Fair Value, Recurring [Member] | Level 2 [Member] | Other [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		118	315
Fair Value, Recurring [Member] | Level 2 [Member] | Total other securities owned at fair value [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		92	81
Fair Value, Recurring [Member] | Level 2 [Member] | Equity, corporate debt, and other securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		67	55
Fair Value, Recurring [Member] | Level 2 [Member] | Mutual Funds And Exchange Traded Funds (ETFs) [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		0	0
Fair Value, Recurring [Member] | Level 2 [Member] | State and municipal debt obligations [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		23	25
Fair Value, Recurring [Member] | Level 2 [Member] | Interest Rate Swaps [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		1
Fair Value, Recurring [Member] | Level 2 [Member] | Other [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Total accrued expenses and other liabilities		46	43
Fair Value, Recurring [Member] | Level 3 [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:		0	0
Investments segregated and on deposit for regulatory purposes:		0	0
Fair Value		0	0
Other assets:		0	0
Total assets		0	0
Total accrued expenses and other liabilities		0	0
Total liabilities		0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Money market funds [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:		0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Commercial paper [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents:			0
Fair Value, Recurring [Member] | Level 3 [Member] | U.S. Government securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Investments segregated and on deposit for regulatory purposes:		0	0
Other assets:		0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Certificates of deposit [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Investments segregated and on deposit for regulatory purposes:		0	0
Fair Value		0	0
Fair Value, Recurring [Member] | Level 3 [Member] | U.S. agency mortgage-backed securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		0	0
Fair Value, Recurring [Member] | Level 3 [Member] | U.S. Treasury securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Asset-backed securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Corporate debt securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Foreign government agency securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		0	0
Fair Value, Recurring [Member] | Level 3 [Member] | U.S. state and municipal securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Non-agency commercial mortgage-backed securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Other [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value		0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Total other securities owned at fair value [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Equity, corporate debt, and other securities [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Mutual Funds And Exchange Traded Funds (ETFs) [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		0	0
Fair Value, Recurring [Member] | Level 3 [Member] | State and municipal debt obligations [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Interest Rate Swaps [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets:		0
Fair Value, Recurring [Member] | Level 3 [Member] | Other [Member]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Line Items]
Total accrued expenses and other liabilities		$ 0	$ 0

[1] Certain prior year amounts have been reclassified to conform to the current year presentation. See Note 1 for additional information.