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Significant Accounting Policies (Schedule Of Securities Segregated For Regulatory Purposes) (Details) - USD ($) $ in Millions		Mar. 31, 2021	Dec. 31, 2020
Marketable Securities [Line Items]
Securities - segregated for regulatory purposes		$ 25,069	$ 27,821
US Government Securities [Member]
Marketable Securities [Line Items]
Securities - segregated for regulatory purposes		3,925	4,750
Securities Purchased Under Agreement To Resell [Member]
Marketable Securities [Line Items]
Securities - segregated for regulatory purposes	[1]	$ 21,144	$ 23,071
[1] These balances are collateralized by U.S. government securities.

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Securities deposited in a special reserve account for the exclusive benefit of customers pursuant to SEC Regulations.

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