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Significant Accounting Policies (Schedule Of Securities Segregated For Regulatory Purposes) (Details) - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018
Marketable Securities [Line Items]
Securities - segregated for regulatory purposes		$ 17,824	$ 15,595
US Government Securities [Member]
Marketable Securities [Line Items]
Securities - segregated for regulatory purposes		3,800	4,200
Securities Purchased Under Agreement To Resell [Member]
Marketable Securities [Line Items]
Securities - segregated for regulatory purposes	[1]	$ 14,000	$ 11,400
[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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