Regulatory Requirements (Net Capital and Net Capital Requirements) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Banking and Thrift [Abstract]
Net Capital	$ 2,166,000	$ 3,700,000
Minimum net capital required	1,000	250
2% of aggregate debit balances	595,000	446,000
Net Capital in excess of required net capital	$ 1,571,000	$ 3,254,000

Amount of net capital in excess of minimum required net capital, calculated under Alternative Standard.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher SEC
-Name Rule 15c3-1
-Number 240
-Section 15c3-1

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Minimum amount of net capital required to be maintained by broker-dealer and its subsidiary, calculated under Aggregate Indebtedness Standard.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher SEC
-Name Rule 15c3-1
-Number 240
-Section 15c3-1

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Amount of net capital of broker-dealer.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher SEC
-Name Rule 15c3-1
-Number 240
-Section 15c3-1

Minimum amount of net capital of broker-dealer parent, calculated under Alternative Standard.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher SEC
-Name Rule 15c3-1
-Number 240
-Section 15c3-1

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No definition available.

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