Bank Loans (Aging Of The Recorded Investment In Past Due Loans) (Details) - USD ($)		Jun. 30, 2021		Dec. 31, 2020
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		$ 15,670,000		$ 18,241,000
Current Balance		12,883,137,000		11,152,572,000
Total		12,898,807,000		11,170,813,000
Non-Accrual		8,280,000	[1]	12,395,000	[2]
Restructured		157,000	[1]	158,000	[2]
Nonperforming loans with no allowance		1,249,000	[1]	1,249,000	[2]
Total		9,686,000	[1]	13,802,000	[2]
Loans past due 90 days and still accruing interest		0		0
Non-Accrual		8,280,000	[1]	12,395,000	[2]
30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		6,141,000		4,611,000
90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		9,529,000		13,630,000
Residential Mortgage
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		8,509,000		5,803,000
Current Balance		4,558,958,000		3,950,867,000
Total		4,567,467,000		3,956,670,000
Non-Accrual	[1]	1,148,000
Restructured		157,000	[1]	158,000	[2]
Nonperforming loans with no allowance		1,249,000	[1]	1,249,000	[2]
Total		2,554,000	[1]	1,407,000	[2]
Non-Accrual	[1]	1,148,000
Residential Mortgage | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		6,112,000		4,554,000
Residential Mortgage | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		2,397,000		1,249,000
Commercial And Industrial
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		7,096,000		12,251,000
Current Balance		4,943,420,000		4,283,838,000
Total		4,950,516,000		4,296,089,000
Non-Accrual		7,096,000	[1]	12,251,000	[2]
Total		7,096,000	[1]	12,251,000	[2]
Non-Accrual		7,096,000	[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		7,096,000		12,237,000
Securities-Based Loans [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Current Balance		2,331,737,000		1,933,974,000
Total		2,331,737,000		1,933,974,000
Commercial Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		36,000		144,000
Current Balance		370,481,000		366,341,000
Total		370,517,000		366,485,000
Non-Accrual		36,000	[1]	144,000	[2]
Total		36,000	[1]	144,000	[2]
Non-Accrual		36,000	[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		36,000		144,000
Home Equity Lines Of Credit [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		16,000		12,000
Current Balance		76,823,000		75,495,000
Total		76,839,000		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		16,000		12,000
Construction And Land [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Current Balance		563,552,000		501,681,000
Total		563,552,000		501,681,000
Other [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		13,000		31,000
Current Balance		38,166,000		40,376,000
Total		38,179,000		40,407,000
Other [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		$ 13,000		$ 31,000

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

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