Fair Values of Assets and Liabilities (Fair Value of Other Financial Instruments) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Assets:
Securities held to maturity, fair value	$ 107,382	$ 74,444
Carrying Amount [Member]
Assets:
Cash and cash equivalents	7,693	9,314
Cash and investments segregated and on deposit for regulatory purposes	12,821	13,533
Receivables from brokers, dealers, and clearing organizations	721	728
Receivables from brokerage clients – net	16,726	17,151
Securities held to maturity, fair value	107,971	75,203
Bank loans	15,548	15,403
Other assets	276	328
Total assets	161,756	131,660
Liabilities:
Bank deposits	166,889	163,454
Payables to brokers, dealers, and clearing organizations	2,643	2,407
Payables to brokerage clients	34,267	35,894
Accrued expenses and other liabilities	996	1,169
Short-term borrowings	600
Long-term debt	3,518	2,876
Total	208,913	205,800
Carrying Amount [Member] | Residential real estate mortgages [Member]
Assets:
Bank loans	9,381	9,117
Carrying Amount [Member] | Home equity loans and lines of credit [Member]
Assets:
Bank loans	2,222	2,342
Carrying Amount [Member] | Pledged Asset Lines [Member]
Assets:
Bank loans	3,845	3,851
Carrying Amount [Member] | Other [Member]
Assets:
Bank loans	100	93
Carrying Amount [Member] | U.S. agency mortgage-backed securities [Member]
Assets:
Securities held to maturity, fair value	90,154	72,439
Carrying Amount [Member] | Non-agency commercial mortgage-backed securities [Member]
Assets:
Securities held to maturity, fair value	996	997
Carrying Amount [Member] | Asset-backed securities [Member]
Assets:
Securities held to maturity, fair value	11,950	941
Carrying Amount [Member] | Corporate debt securities [Member]
Assets:
Securities held to maturity, fair value	3,179	436
Carrying Amount [Member] | U.S. Treasury securities [Member]
Assets:
Securities held to maturity, fair value	223	223
Carrying Amount [Member] | Commercial paper [Member]
Assets:
Securities held to maturity, fair value	99	99
Carrying Amount [Member] | U.S. state and municipal securities [Member]
Assets:
Securities held to maturity, fair value	1,170	68
Carrying Amount [Member] | Certificates of deposit [Member]
Assets:
Securities held to maturity, fair value	200
Portion at Other than Fair Value Measurement [Member]
Assets:
Cash and cash equivalents	7,693	9,314
Cash and investments segregated and on deposit for regulatory purposes	12,821	13,533
Receivables from brokers, dealers, and clearing organizations	721	728
Receivables from brokerage clients – net	16,726	17,151
Securities held to maturity, fair value	107,382	74,444
Bank loans	15,628	15,467
Other assets	276	328
Total assets	161,247	130,965
Liabilities:
Bank deposits	166,889	163,454
Payables to brokers, dealers, and clearing organizations	2,643	2,407
Payables to brokerage clients	34,267	35,894
Accrued expenses and other liabilities	996	1,169
Short-term borrowings	600
Long-term debt	3,576	2,941
Total	208,971	205,865
Portion at Other than Fair Value Measurement [Member] | Residential real estate mortgages [Member]
Assets:
Bank loans	9,368	9,064
Portion at Other than Fair Value Measurement [Member] | Home equity loans and lines of credit [Member]
Assets:
Bank loans	2,315	2,458
Portion at Other than Fair Value Measurement [Member] | Pledged Asset Lines [Member]
Assets:
Bank loans	3,845	3,851
Portion at Other than Fair Value Measurement [Member] | Other [Member]
Assets:
Bank loans	100	94
Portion at Other than Fair Value Measurement [Member] | U.S. agency mortgage-backed securities [Member]
Assets:
Securities held to maturity, fair value	89,511	71,677
Portion at Other than Fair Value Measurement [Member] | Non-agency commercial mortgage-backed securities [Member]
Assets:
Securities held to maturity, fair value	1,001	1,004
Portion at Other than Fair Value Measurement [Member] | Asset-backed securities [Member]
Assets:
Securities held to maturity, fair value	11,966	941
Portion at Other than Fair Value Measurement [Member] | Corporate debt securities [Member]
Assets:
Securities held to maturity, fair value	3,195	436
Portion at Other than Fair Value Measurement [Member] | U.S. Treasury securities [Member]
Assets:
Securities held to maturity, fair value	220	219
Portion at Other than Fair Value Measurement [Member] | Commercial paper [Member]
Assets:
Securities held to maturity, fair value	99	99
Portion at Other than Fair Value Measurement [Member] | U.S. state and municipal securities [Member]
Assets:
Securities held to maturity, fair value	1,190	68
Portion at Other than Fair Value Measurement [Member] | Certificates of deposit [Member]
Assets:
Securities held to maturity, fair value	200
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
Securities held to maturity, fair value	0	0
Bank loans	0	0
Other assets	0	0
Total assets	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	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	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	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	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:
Securities held to maturity, fair value	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:
Securities held to maturity, fair value	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:
Securities held to maturity, fair value	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:
Securities held to maturity, fair value	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:
Securities held to maturity, fair value	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:
Securities held to maturity, fair value	0	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:
Securities held to maturity, fair value	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:
Securities held to maturity, fair value	0
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets:
Cash and cash equivalents	7,693	9,314
Cash and investments segregated and on deposit for regulatory purposes	12,821	13,533
Receivables from brokers, dealers, and clearing organizations	721	728
Receivables from brokerage clients – net	16,726	17,151
Securities held to maturity, fair value	107,382	74,444
Bank loans	15,628	15,467
Other assets	276	328
Total assets	161,247	130,965
Liabilities:
Bank deposits	166,889	163,454
Payables to brokers, dealers, and clearing organizations	2,643	2,407
Payables to brokerage clients	34,267	35,894
Accrued expenses and other liabilities	996	1,169
Short-term borrowings	600
Long-term debt	3,576	2,941
Total	208,971	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	9,368	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	2,315	2,458
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | Pledged Asset Lines [Member]
Assets:
Bank loans	3,845	3,851
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other [Member]
Assets:
Bank loans	100	94
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | U.S. agency mortgage-backed securities [Member]
Assets:
Securities held to maturity, fair value	89,511	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:
Securities held to maturity, fair value	1,001	1,004
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | Asset-backed securities [Member]
Assets:
Securities held to maturity, fair value	11,966	941
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate debt securities [Member]
Assets:
Securities held to maturity, fair value	3,195	436
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | U.S. Treasury securities [Member]
Assets:
Securities held to maturity, fair value	220	219
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | Commercial paper [Member]
Assets:
Securities held to maturity, fair value	99	99
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | U.S. state and municipal securities [Member]
Assets:
Securities held to maturity, fair value	1,190	68
Portion at Other than Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member] | Certificates of deposit [Member]
Assets:
Securities held to maturity, fair value	200
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
Securities held to maturity, fair value	0	0
Bank loans	0	0
Other assets	0	0
Total assets	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	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	0	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | Pledged Asset Lines [Member]
Assets:
Bank loans	0	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | Other [Member]
Assets:
Bank loans	0	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | U.S. agency mortgage-backed securities [Member]
Assets:
Securities held to maturity, fair value	0	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | Non-agency commercial mortgage-backed securities [Member]
Assets:
Securities held to maturity, fair value	0	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | Asset-backed securities [Member]
Assets:
Securities held to maturity, fair value	0	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | Corporate debt securities [Member]
Assets:
Securities held to maturity, fair value	0	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | U.S. Treasury securities [Member]
Assets:
Securities held to maturity, fair value	0	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | Commercial paper [Member]
Assets:
Securities held to maturity, fair value	0	0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | U.S. state and municipal securities [Member]
Assets:
Securities held to maturity, fair value	0	$ 0
Portion at Other than Fair Value Measurement [Member] | Significant Unobservable Inputs (Level 3) [Member] | Certificates of deposit [Member]
Assets:
Securities held to maturity, fair value	$ 0