Bank Loans (Aging Of The Recorded Investment In Past Due Loans) (Details) - USD ($)		Sep. 30, 2021		Dec. 31, 2020
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		$ 12,065,000		$ 18,241,000
Total		13,631,287,000		11,170,813,000
Non-Accrual		6,922,000	[1]	12,395,000	[2]
Restructured		156,000	[1]	158,000	[2]
Nonperforming loans with no allowance		1,249,000	[1]	1,249,000	[2]
Total		8,327,000	[1]	13,802,000	[2]
Loans past due 90 days and still accruing interest		0		0
Non-Accrual		6,922,000	[1]	12,395,000	[2]
30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		3,894,000		4,611,000
90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		8,171,000		13,630,000
Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		13,619,222,000		11,152,572,000
Residential Mortgage
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		5,227,000		5,803,000
Total		4,952,372,000		3,956,670,000
Non-Accrual	[1]	84,000
Restructured		156,000	[1]	158,000	[2]
Nonperforming loans with no allowance		1,249,000	[1]	1,249,000	[2]
Total		1,489,000	[1]	1,407,000	[2]
Non-Accrual	[1]	84,000
Residential Mortgage | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		3,894,000		4,554,000
Residential Mortgage | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		1,333,000		1,249,000
Residential Mortgage | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		4,947,145,000		3,950,867,000
Commercial And Industrial
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		6,805,000		12,251,000
Total		5,033,313,000		4,296,089,000
Non-Accrual		6,805,000	[1]	12,251,000	[2]
Total		6,805,000	[1]	12,251,000	[2]
Non-Accrual		6,805,000	[1]	12,251,000	[2]
Commercial And Industrial | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due				14,000
Commercial And Industrial | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		6,805,000		12,237,000
Commercial And Industrial | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		5,026,508,000		4,283,838,000
Securities-Based Loans [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		2,581,705,000		1,933,974,000
Securities-Based Loans [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		2,581,705,000		1,933,974,000
Commercial Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		33,000		144,000
Total		369,502,000		366,485,000
Non-Accrual		33,000	[1]	144,000	[2]
Total		33,000	[1]	144,000	[2]
Non-Accrual		33,000	[1]	144,000	[2]
Commercial Real Estate [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		33,000		144,000
Commercial Real Estate [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		369,469,000		366,341,000
Home Equity Lines Of Credit [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due				12,000
Total		82,230,000		75,507,000
Home Equity Lines Of Credit [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due				12,000
Home Equity Lines Of Credit [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		82,230,000		75,495,000
Construction And Land [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		576,362,000		501,681,000
Construction And Land [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		576,362,000		501,681,000
Other [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due				31,000
Total		35,803,000		40,407,000
Other [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due				31,000
Other [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		$ 35,803,000		$ 40,376,000

[1] There were no loans past due 90 days and still accruing interest at September 30, 2021.

[2] There were no loans past due 90 days and still accruing interest at December 31, 2020.