Bank Loans (Aging Of The Recorded Investment In Past Due Loans) (Details) - USD ($)	Jun. 30, 2019		Dec. 31, 2018
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	$ 17,827,000		$ 22,170,000
Current Balance	9,048,451,000		8,559,477,000
Recorded Investment in Loans, Total	9,066,278,000		8,581,647,000
Non-Accrual	15,515,000	[1]	15,298,000	[2]
Restructured	7,881,000	[1]	9,103,000	[2]
Total	23,396,000	[1]	24,401,000	[2]
Loans past due 90 days and still accruing interest	0		0
30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	2,569,000		7,003,000
90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	15,258,000		15,167,000
Commercial And Industrial [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	14,211,000		14,656,000
Current Balance	3,323,916,000		3,289,578,000
Recorded Investment in Loans, Total	3,338,127,000		3,304,234,000
Non-Accrual	14,211,000	[1]	14,741,000	[2]
Restructured	7,715,000	[1]	8,936,000	[2]
Total	21,926,000	[1]	23,677,000	[2]
Commercial And Industrial [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	14,211,000		14,656,000
Residential Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	3,277,000		7,347,000
Current Balance	2,981,448,000		2,867,667,000
Recorded Investment in Loans, Total	2,984,725,000		2,875,014,000
Non-Accrual	955,000	[1]	352,000	[2]
Restructured	166,000	[1]	167,000	[2]
Total	1,121,000	[1]	519,000	[2]
Residential Real Estate [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	2,385,000		6,970,000
Residential Real Estate [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	892,000		377,000
Securities-Based Loans [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Current Balance	1,962,528,000		1,786,966,000
Recorded Investment in Loans, Total	1,962,528,000		1,786,966,000
Commercial Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Current Balance	367,283,000		318,961,000
Recorded Investment in Loans, Total	367,283,000		318,961,000
Construction And Land [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Current Balance	226,559,000		138,245,000
Recorded Investment in Loans, Total	226,559,000		138,245,000
Home Equity Lines Of Credit [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	184,000		33,000
Current Balance	49,025,000		38,065,000
Recorded Investment in Loans, Total	49,209,000		38,098,000
Non-Accrual	184,000	[1]	184,000	[2]
Total	184,000	[1]	184,000	[2]
Home Equity Lines Of Credit [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	184,000		33,000
Other [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	155,000		134,000
Current Balance	137,692,000		119,995,000
Recorded Investment in Loans, Total	137,847,000		120,129,000
Non-Accrual	165,000	[1]	21,000	[2]
Total	165,000	[1]	21,000	[2]
Other [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due	$ 155,000		$ 134,000

[1] There were no loans past due 90 days and still accruing interest at June 30, 2019.

[2] There were no loans past due 90 days and still accruing interest at December 31, 2018.