Fair Values of Assets and Liabilities (Fair Value of Other Financial Instruments) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Assets:
Held to maturity securities	$ 114,332	$ 74,444
Carrying Amount [Member]
Assets:
Cash and cash equivalents	10,418	9,314
Cash and investments segregated and on deposit for regulatory purposes	10,916	13,533
Receivables from brokers, dealers, and clearing organizations	665	728
Receivables from brokerage clients – net	18,456	17,151
Held to maturity securities	114,376	75,203
Bank loans – net	16,232	15,403
Other assets	465	328
Total	171,528	131,660
Liabilities:
Bank deposits	165,263	163,454
Payables to brokers, dealers, and clearing organizations	5,427	2,407
Payables to brokerage clients	31,480	35,894
Accrued expenses and other liabilities	1,067	1,169
Short-term borrowings	5,000
Long-term debt	3,268	2,876
Total	211,505	205,800
Carrying Amount [Member] | Residential real estate mortgages [Member]
Assets:
Bank loans – net	9,786	9,117
Carrying Amount [Member] | Home equity loans and lines of credit [Member]
Assets:
Bank loans – net	2,034	2,342
Carrying Amount [Member] | Pledged asset lines [Member]
Assets:
Bank loans – net	4,279	3,851
Carrying Amount [Member] | Other [Member]
Assets:
Bank loans – net	133	93
Carrying Amount [Member] | U.S. agency mortgage-backed securities [Member]
Assets:
Held to maturity securities	96,045	72,439
Carrying Amount [Member] | Non-agency commercial mortgage-backed securities [Member]
Assets:
Held to maturity securities	995	997
Carrying Amount [Member] | Asset-backed securities [Member]
Assets:
Held to maturity securities	12,237	941
Carrying Amount [Member] | Corporate debt securities [Member]
Assets:
Held to maturity securities	3,377	436
Carrying Amount [Member] | U.S. Treasury securities [Member]
Assets:
Held to maturity securities	223	223
Carrying Amount [Member] | Commercial paper [Member]
Assets:
Held to maturity securities		99
Carrying Amount [Member] | U.S. state and municipal securities [Member]
Assets:
Held to maturity securities	1,249	68
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
Portion at Other than Fair Value Measurement [Member]
Assets:
Cash and cash equivalents	10,418	9,314
Cash and investments segregated and on deposit for regulatory purposes	10,916	13,533
Receivables from brokers, dealers, and clearing organizations	665	728
Receivables from brokerage clients – net	18,456	17,151
Held to maturity securities	114,332	74,444
Bank loans – net	16,310	15,467
Other assets	465	328
Total	171,562	130,965
Liabilities:
Bank deposits	165,263	163,454
Payables to brokers, dealers, and clearing organizations	5,427	2,407
Payables to brokerage clients	31,480	35,894
Accrued expenses and other liabilities	1,067	1,169
Short-term borrowings	5,000
Long-term debt	3,347	2,941
Total	211,584	205,865
Portion at Other than Fair Value Measurement [Member] | Residential real estate mortgages [Member]
Assets:
Bank loans – net	9,771	9,064
Portion at Other than Fair Value Measurement [Member] | Home equity loans and lines of credit [Member]
Assets:
Bank loans – net	2,127	2,458
Portion at Other than Fair Value Measurement [Member] | Pledged asset lines [Member]
Assets:
Bank loans – net	4,279	3,851
Portion at Other than Fair Value Measurement [Member] | Other [Member]
Assets:
Bank loans – net	133	94
Portion at Other than Fair Value Measurement [Member] | U.S. agency mortgage-backed securities [Member]
Assets:
Held to maturity securities	95,816	71,677
Portion at Other than Fair Value Measurement [Member] | Non-agency commercial mortgage-backed securities [Member]
Assets:
Held to maturity securities	1,006	1,004
Portion at Other than Fair Value Measurement [Member] | Asset-backed securities [Member]
Assets:
Held to maturity securities	12,336	941
Portion at Other than Fair Value Measurement [Member] | Corporate debt securities [Member]
Assets:
Held to maturity securities	3,403	436
Portion at Other than Fair Value Measurement [Member] | U.S. Treasury securities [Member]
Assets:
Held to maturity securities	222	219
Portion at Other than Fair Value Measurement [Member] | Commercial paper [Member]
Assets:
Held to maturity securities		99
Portion at Other than Fair Value Measurement [Member] | U.S. state and municipal securities [Member]
Assets:
Held to maturity securities	1,299	68
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] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets:
Cash and cash equivalents	0	0
Cash and investments segregated and on deposit for regulatory purposes	0	0
Receivables from brokers, dealers, and clearing organizations	0	0
Receivables from brokerage clients – net	0	0
Held to maturity securities	0	0
Bank loans – net	0	0
Other assets	0	0
Total	0	0
Liabilities:
Bank deposits	0	0
Payables to brokers, dealers, and clearing organizations	0	0
Payables to brokerage clients	0	0
Accrued expenses and other liabilities	0	0
Short-term borrowings	0
Long-term debt	0	0
Total	0	0
Portion at Other than Fair Value Measurement [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Residential real estate mortgages [Member]
Assets:
Bank loans – net	0	0
Portion at Other than Fair Value Measurement [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Home equity loans and lines of credit [Member]
Assets:
Bank loans – net	0	0
Portion at Other than Fair Value Measurement [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pledged asset lines [Member]
Assets:
Bank loans – net	0	0
Portion at Other than Fair Value Measurement [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other [Member]
Assets:
Bank loans – net	0	0
Portion at Other than Fair Value Measurement [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. agency mortgage-backed securities [Member]
Assets:
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Non-agency commercial mortgage-backed securities [Member]
Assets:
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Asset-backed securities [Member]
Assets:
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate debt securities [Member]
Assets:
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. Treasury securities [Member]
Assets:
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Commercial paper [Member]
Assets:
Held to maturity securities		0
Portion at Other than Fair Value Measurement [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | U.S. state and municipal securities [Member]
Assets:
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Certificates of deposit [Member]
Assets:
Held to maturity securities	0
Portion at Other than Fair Value Measurement [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Foreign government agency securities [Member]
Assets:
Held to maturity securities	0
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets:
Cash and cash equivalents	10,418	9,314
Cash and investments segregated and on deposit for regulatory purposes	10,916	13,533
Receivables from brokers, dealers, and clearing organizations	665	728
Receivables from brokerage clients – net	18,456	17,151
Held to maturity securities	114,332	74,444
Bank loans – net	16,310	15,467
Other assets	465	328
Total	171,562	130,965
Liabilities:
Bank deposits	165,263	163,454
Payables to brokers, dealers, and clearing organizations	5,427	2,407
Payables to brokerage clients	31,480	35,894
Accrued expenses and other liabilities	1,067	1,169
Short-term borrowings	5,000
Long-term debt	3,347	2,941
Total	211,584	205,865
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | Residential real estate mortgages [Member]
Assets:
Bank loans – net	9,771	9,064
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | Home equity loans and lines of credit [Member]
Assets:
Bank loans – net	2,127	2,458
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pledged asset lines [Member]
Assets:
Bank loans – net	4,279	3,851
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other [Member]
Assets:
Bank loans – net	133	94
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | U.S. agency mortgage-backed securities [Member]
Assets:
Held to maturity securities	95,816	71,677
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | Non-agency commercial mortgage-backed securities [Member]
Assets:
Held to maturity securities	1,006	1,004
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | Asset-backed securities [Member]
Assets:
Held to maturity securities	12,336	941
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate debt securities [Member]
Assets:
Held to maturity securities	3,403	436
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | U.S. Treasury securities [Member]
Assets:
Held to maturity securities	222	219
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | Commercial paper [Member]
Assets:
Held to maturity securities		99
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | U.S. state and municipal securities [Member]
Assets:
Held to maturity securities	1,299	68
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | Certificates of deposit [Member]
Assets:
Held to maturity securities	200
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | Foreign government agency securities [Member]
Assets:
Held to maturity securities	50
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets:
Cash and cash equivalents	0	0
Cash and investments segregated and on deposit for regulatory purposes	0	0
Receivables from brokers, dealers, and clearing organizations	0	0
Receivables from brokerage clients – net	0	0
Held to maturity securities	0	0
Bank loans – net	0	0
Other assets	0	0
Total	0	0
Liabilities:
Bank deposits	0	0
Payables to brokers, dealers, and clearing organizations	0	0
Payables to brokerage clients	0	0
Accrued expenses and other liabilities	0	0
Short-term borrowings	0
Long-term debt	0	0
Total	0	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | Residential real estate mortgages [Member]
Assets:
Bank loans – net	0	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | Home equity loans and lines of credit [Member]
Assets:
Bank loans – net	0	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pledged asset lines [Member]
Assets:
Bank loans – net	0	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other [Member]
Assets:
Bank loans – net	0	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | U.S. agency mortgage-backed securities [Member]
Assets:
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | Non-agency commercial mortgage-backed securities [Member]
Assets:
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | Asset-backed securities [Member]
Assets:
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | Corporate debt securities [Member]
Assets:
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | U.S. Treasury securities [Member]
Assets:
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | Commercial paper [Member]
Assets:
Held to maturity securities		0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | U.S. state and municipal securities [Member]
Assets:
Held to maturity securities	0	$ 0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | Certificates of deposit [Member]
Assets:
Held to maturity securities	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | Foreign government agency securities [Member]
Assets:
Held to maturity securities	$ 0