Fair Values of Assets and Liabilities (Fair Value of Other Financial Instruments) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Assets
Held to maturity securities	$ 142,163	$ 142,038
U.S. agency mortgage-backed securities [Member]
Assets
Held to maturity securities	116,012	116,093
Asset-backed securities [Member]
Assets
Held to maturity securities	18,359	18,546
Corporate debt securities [Member]
Assets
Held to maturity securities	4,715	4,432
U.S. state and municipal securities [Member]
Assets
Held to maturity securities	1,413	1,348
Non-agency commercial mortgage-backed securities [Member]
Assets
Held to maturity securities	1,164	1,142
U.S. Treasury securities [Member]
Assets
Held to maturity securities	230	217
Certificates of deposit [Member]
Assets
Held to maturity securities	200	201
Foreign government agency securities [Member]
Assets
Held to maturity securities	50	49
Carrying Amount [Member]
Assets
Cash and cash equivalents	15,136	19,646
Cash and investments segregated and on deposit for regulatory purposes	12,595	8,886
Receivables from brokers, dealers, and clearing organizations	1,317	553
Receivables from brokerage clients — net	21,061	21,641
Held to maturity securities	140,194	144,009
Bank loans – net	16,895	16,609
Other assets	617	460
Total	207,815	211,804
Liabilities
Bank deposits	209,327	231,423
Payables to brokers, dealers, and clearing organizations	1,736	1,831
Payables to brokerage clients	35,622	32,726
Accrued expenses and other liabilities	1,252	1,370
Long-term debt	7,427	6,878
Total	255,364	274,228
Carrying Amount [Member] | First Mortgage [Member]
Assets
Bank loans – net	10,630	10,370
Carrying Amount [Member] | HELOCs [Member]
Assets
Bank loans – net	1,216	1,500
Carrying Amount [Member] | Pledged asset lines [Member]
Assets
Bank loans – net	4,878	4,561
Carrying Amount [Member] | Other [Member]
Assets
Bank loans – net	171	178
Carrying Amount [Member] | U.S. agency mortgage-backed securities [Member]
Assets
Held to maturity securities	114,276	118,064
Carrying Amount [Member] | Asset-backed securities [Member]
Assets
Held to maturity securities	18,323	18,502
Carrying Amount [Member] | Corporate debt securities [Member]
Assets
Held to maturity securities	4,659	4,477
Carrying Amount [Member] | U.S. state and municipal securities [Member]
Assets
Held to maturity securities	1,306	1,327
Carrying Amount [Member] | Non-agency commercial mortgage-backed securities [Member]
Assets
Held to maturity securities	1,136	1,156
Carrying Amount [Member] | U.S. Treasury securities [Member]
Assets
Held to maturity securities	224	223
Carrying Amount [Member] | Certificates of deposit [Member]
Assets
Held to maturity securities	200	200
Carrying Amount [Member] | Foreign government agency securities [Member]
Assets
Held to maturity securities	50	50
Carrying Amount [Member] | Other [Member]
Assets
Held to maturity securities	20	10
Portion at Other than Fair Value Measurement [Member]
Assets
Cash and cash equivalents	15,136	19,646
Cash and investments segregated and on deposit for regulatory purposes	12,595	8,886
Receivables from brokers, dealers, and clearing organizations	1,317	553
Receivables from brokerage clients — net	21,061	21,641
Held to maturity securities	142,163	142,038
Bank loans – net	16,986	16,515
Other assets	617	460
Total	209,875	209,739
Liabilities
Bank deposits	209,327	231,423
Payables to brokers, dealers, and clearing organizations	1,736	1,831
Payables to brokerage clients	35,622	32,726
Accrued expenses and other liabilities	1,252	1,370
Long-term debt	7,771	6,827
Total	255,708	274,177
Portion at Other than Fair Value Measurement [Member] | First Mortgage [Member]
Assets
Bank loans – net	10,682	10,193
Portion at Other than Fair Value Measurement [Member] | HELOCs [Member]
Assets
Bank loans – net	1,255	1,583
Portion at Other than Fair Value Measurement [Member] | Pledged asset lines [Member]
Assets
Bank loans – net	4,878	4,561
Portion at Other than Fair Value Measurement [Member] | Other [Member]
Assets
Bank loans – net	171	178
Portion at Other than Fair Value Measurement [Member] | U.S. agency mortgage-backed securities [Member]
Assets
Held to maturity securities	116,012	116,093
Portion at Other than Fair Value Measurement [Member] | Asset-backed securities [Member]
Assets
Held to maturity securities	18,359	18,546
Portion at Other than Fair Value Measurement [Member] | Corporate debt securities [Member]
Assets
Held to maturity securities	4,715	4,432
Portion at Other than Fair Value Measurement [Member] | U.S. state and municipal securities [Member]
Assets
Held to maturity securities	1,413	1,348
Portion at Other than Fair Value Measurement [Member] | Non-agency commercial mortgage-backed securities [Member]
Assets
Held to maturity securities	1,164	1,142
Portion at Other than Fair Value Measurement [Member] | U.S. Treasury securities [Member]
Assets
Held to maturity securities	230	217
Portion at Other than Fair Value Measurement [Member] | Certificates of deposit [Member]
Assets
Held to maturity securities	200	201
Portion at Other than Fair Value Measurement [Member] | Foreign government agency securities [Member]
Assets
Held to maturity securities	50	49
Portion at Other than Fair Value Measurement [Member] | Other [Member]
Assets
Held to maturity securities	20	10
Portion at Other than Fair Value Measurement [Member] | 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
Long-term debt	0	0
Total	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	0
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member] | Asset-backed securities [Member]
Assets
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member] | Corporate debt securities [Member]
Assets
Held to maturity securities	0	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	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	0
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member] | U.S. Treasury securities [Member]
Assets
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member] | Certificates of deposit [Member]
Assets
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member] | Foreign government agency securities [Member]
Assets
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Level 1 [Member] | Other [Member]
Assets
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member]
Assets
Cash and cash equivalents	15,136	19,646
Cash and investments segregated and on deposit for regulatory purposes	12,595	8,886
Receivables from brokers, dealers, and clearing organizations	1,317	553
Receivables from brokerage clients — net	21,061	21,641
Held to maturity securities	142,163	142,038
Bank loans – net	16,986	16,515
Other assets	617	460
Total	209,875	209,739
Liabilities
Bank deposits	209,327	231,423
Payables to brokers, dealers, and clearing organizations	1,736	1,831
Payables to brokerage clients	35,622	32,726
Accrued expenses and other liabilities	1,252	1,370
Long-term debt	7,771	6,827
Total	255,708	274,177
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | First Mortgage [Member]
Assets
Bank loans – net	10,682	10,193
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | HELOCs [Member]
Assets
Bank loans – net	1,255	1,583
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | Pledged asset lines [Member]
Assets
Bank loans – net	4,878	4,561
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | Other [Member]
Assets
Bank loans – net	171	178
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | U.S. agency mortgage-backed securities [Member]
Assets
Held to maturity securities	116,012	116,093
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | Asset-backed securities [Member]
Assets
Held to maturity securities	18,359	18,546
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | Corporate debt securities [Member]
Assets
Held to maturity securities	4,715	4,432
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | U.S. state and municipal securities [Member]
Assets
Held to maturity securities	1,413	1,348
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | Non-agency commercial mortgage-backed securities [Member]
Assets
Held to maturity securities	1,164	1,142
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | U.S. Treasury securities [Member]
Assets
Held to maturity securities	230	217
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | Certificates of deposit [Member]
Assets
Held to maturity securities	200	201
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | Foreign government agency securities [Member]
Assets
Held to maturity securities	50	49
Portion at Other than Fair Value Measurement [Member] | Level 2 [Member] | Other [Member]
Assets
Held to maturity securities	20	10
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 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
Long-term debt	0	0
Total	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	0
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member] | Asset-backed securities [Member]
Assets
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member] | Corporate debt securities [Member]
Assets
Held to maturity securities	0	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	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	0
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member] | U.S. Treasury securities [Member]
Assets
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member] | Certificates of deposit [Member]
Assets
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member] | Foreign government agency securities [Member]
Assets
Held to maturity securities	0	0
Portion at Other than Fair Value Measurement [Member] | Level 3 [Member] | Other [Member]
Assets
Held to maturity securities	$ 0	$ 0