Fair Values of Assets and Liabilities (Fair Value of Other Financial Instruments) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Assets
Held to maturity securities		$ 136,099
U.S. agency mortgage-backed securities [Member]
Assets
Held to maturity securities		110,566
Asset-backed securities [Member]
Assets
Held to maturity securities		17,771
Corporate debt securities [Member]
Assets
Held to maturity securities		4,718
U.S. state and municipal securities [Member]
Assets
Held to maturity securities		1,404
Non-agency commercial mortgage-backed securities [Member]
Assets
Held to maturity securities		1,141
U.S. Treasury securities [Member]
Assets
Held to maturity securities		228
Certificates of deposit [Member]
Assets
Held to maturity securities		200
Foreign government agency securities [Member]
Assets
Held to maturity securities		50
Carrying Amount [Member]
Assets
Cash and cash equivalents	$ 23,708	21,668
Cash and investments segregated and on deposit for regulatory purposes	15,494	11,807
Receivables from brokerage clients — net	25,438	21,763
Held to maturity securities		134,706
Bank loans – net	22,286	18,212
Other assets	1,617	1,014
Liabilities
Bank deposits	320,717	220,094
Payables to brokerage clients	52,006	39,220
Accrued expenses and other liabilities	2,208	1,882
Long-term debt	7,829	7,430
Carrying Amount [Member] | First Mortgage [Member]
Assets
Bank loans – net	14,319	11,693
Carrying Amount [Member] | HELOCs [Member]
Assets
Bank loans – net	908	1,113
Carrying Amount [Member] | Pledged asset lines [Member]
Assets
Bank loans – net	6,885	5,206
Carrying Amount [Member] | Other [Member]
Assets
Bank loans – net	174	200
Carrying Amount [Member] | U.S. agency mortgage-backed securities [Member]
Assets
Held to maturity securities		109,325
Carrying Amount [Member] | Asset-backed securities [Member]
Assets
Held to maturity securities		17,806
Carrying Amount [Member] | Corporate debt securities [Member]
Assets
Held to maturity securities		4,661
Carrying Amount [Member] | U.S. state and municipal securities [Member]
Assets
Held to maturity securities		1,301
Carrying Amount [Member] | Non-agency commercial mortgage-backed securities [Member]
Assets
Held to maturity securities		1,119
Carrying Amount [Member] | U.S. Treasury securities [Member]
Assets
Held to maturity securities		223
Carrying Amount [Member] | Certificates of deposit [Member]
Assets
Held to maturity securities		200
Carrying Amount [Member] | Foreign government agency securities [Member]
Assets
Held to maturity securities		50
Carrying Amount [Member] | Other [Member]
Assets
Held to maturity securities		21
Portion at Other than Fair Value Measurement [Member]
Assets
Cash and cash equivalents	23,708	21,668
Cash and investments segregated and on deposit for regulatory purposes	15,494	11,807
Receivables from brokerage clients — net	25,438	21,763
Held to maturity securities		136,099
Bank loans – net	22,692	18,198
Other assets	1,617	1,014
Liabilities
Bank deposits	320,717	220,094
Payables to brokerage clients	52,006	39,220
Accrued expenses and other liabilities	2,208	1,882
Long-term debt	8,717	7,775
Portion at Other than Fair Value Measurement [Member] | First Mortgage [Member]
Assets
Bank loans – net	14,733	11,639
Portion at Other than Fair Value Measurement [Member] | HELOCs [Member]
Assets
Bank loans – net	900	1,153
Portion at Other than Fair Value Measurement [Member] | Pledged asset lines [Member]
Assets
Bank loans – net	6,885	5,206
Portion at Other than Fair Value Measurement [Member] | Other [Member]
Assets
Bank loans – net	174	200
Portion at Other than Fair Value Measurement [Member] | U.S. agency mortgage-backed securities [Member]
Assets
Held to maturity securities		110,566
Portion at Other than Fair Value Measurement [Member] | Asset-backed securities [Member]
Assets
Held to maturity securities		17,771
Portion at Other than Fair Value Measurement [Member] | Corporate debt securities [Member]
Assets
Held to maturity securities		4,718
Portion at Other than Fair Value Measurement [Member] | U.S. state and municipal securities [Member]
Assets
Held to maturity securities		1,404
Portion at Other than Fair Value Measurement [Member] | Non-agency commercial mortgage-backed securities [Member]
Assets
Held to maturity securities		1,141
Portion at Other than Fair Value Measurement [Member] | U.S. Treasury securities [Member]
Assets
Held to maturity securities		228
Portion at Other than Fair Value Measurement [Member] | Certificates of deposit [Member]
Assets
Held to maturity securities		200
Portion at Other than Fair Value Measurement [Member] | Foreign government agency securities [Member]
Assets
Held to maturity securities		50
Portion at Other than Fair Value Measurement [Member] | Other [Member]
Assets
Held to maturity securities		21
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member]
Assets
Cash and cash equivalents	23,708	21,668
Cash and investments segregated and on deposit for regulatory purposes	1,772	2,792
Receivables from brokerage clients — net	0	0
Held to maturity securities		0
Bank loans – net	0	0
Other assets	0	0
Liabilities
Bank deposits	0	0
Payables to brokerage clients	0	0
Accrued expenses and other liabilities	0	0
Long-term debt	0	0
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member] | First Mortgage [Member]
Assets
Bank loans – net	0	0
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member] | HELOCs [Member]
Assets
Bank loans – net	0	0
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member] | Pledged asset lines [Member]
Assets
Bank loans – net	0	0
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member] | Other [Member]
Assets
Bank loans – net	0	0
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member] | U.S. agency mortgage-backed securities [Member]
Assets
Held to maturity securities		0
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member] | Asset-backed securities [Member]
Assets
Held to maturity securities		0
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member] | Corporate debt securities [Member]
Assets
Held to maturity securities		0
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member] | U.S. state and municipal securities [Member]
Assets
Held to maturity securities		0
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member] | Non-agency commercial mortgage-backed securities [Member]
Assets
Held to maturity securities		0
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member] | U.S. Treasury securities [Member]
Assets
Held to maturity securities		0
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member] | Certificates of deposit [Member]
Assets
Held to maturity securities		0
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member] | Foreign government agency securities [Member]
Assets
Held to maturity securities		0
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member] | Other [Member]
Assets
Held to maturity securities		0
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member]
Assets
Cash and cash equivalents	0	0
Cash and investments segregated and on deposit for regulatory purposes	13,722	9,015
Receivables from brokerage clients — net	25,438	21,763
Held to maturity securities		136,099
Bank loans – net	22,692	18,198
Other assets	1,617	1,014
Liabilities
Bank deposits	320,717	220,094
Payables to brokerage clients	52,006	39,220
Accrued expenses and other liabilities	2,208	1,882
Long-term debt	8,717	7,775
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | First Mortgage [Member]
Assets
Bank loans – net	14,733	11,639
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | HELOCs [Member]
Assets
Bank loans – net	900	1,153
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | Pledged asset lines [Member]
Assets
Bank loans – net	6,885	5,206
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | Other [Member]
Assets
Bank loans – net	174	200
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | U.S. agency mortgage-backed securities [Member]
Assets
Held to maturity securities		110,566
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | Asset-backed securities [Member]
Assets
Held to maturity securities		17,771
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | Corporate debt securities [Member]
Assets
Held to maturity securities		4,718
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | U.S. state and municipal securities [Member]
Assets
Held to maturity securities		1,404
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | Non-agency commercial mortgage-backed securities [Member]
Assets
Held to maturity securities		1,141
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | U.S. Treasury securities [Member]
Assets
Held to maturity securities		228
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | Certificates of deposit [Member]
Assets
Held to maturity securities		200
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | Foreign government agency securities [Member]
Assets
Held to maturity securities		50
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | Other [Member]
Assets
Held to maturity securities		21
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member]
Assets
Cash and cash equivalents	0	0
Cash and investments segregated and on deposit for regulatory purposes	0	0
Receivables from brokerage clients — net	0	0
Held to maturity securities		0
Bank loans – net	0	0
Other assets	0	0
Liabilities
Bank deposits	0	0
Payables to brokerage clients	0	0
Accrued expenses and other liabilities	0	0
Long-term debt	0	0
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member] | First Mortgage [Member]
Assets
Bank loans – net	0	0
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member] | HELOCs [Member]
Assets
Bank loans – net	0	0
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member] | Pledged asset lines [Member]
Assets
Bank loans – net	0	0
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member] | Other [Member]
Assets
Bank loans – net	$ 0	0
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member] | U.S. agency mortgage-backed securities [Member]
Assets
Held to maturity securities		0
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member] | Asset-backed securities [Member]
Assets
Held to maturity securities		0
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member] | Corporate debt securities [Member]
Assets
Held to maturity securities		0
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member] | U.S. state and municipal securities [Member]
Assets
Held to maturity securities		0
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member] | Non-agency commercial mortgage-backed securities [Member]
Assets
Held to maturity securities		0
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member] | U.S. Treasury securities [Member]
Assets
Held to maturity securities		0
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member] | Certificates of deposit [Member]
Assets
Held to maturity securities		0
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member] | Foreign government agency securities [Member]
Assets
Held to maturity securities		0
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member] | Other [Member]
Assets
Held to maturity securities		$ 0