Bank Loans (Aging Of The Recorded Investment In Past Due Loans) (Details) - USD ($)		Dec. 31, 2018		Dec. 31, 2017
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		$ 22,170,000		$ 19,961,000
Current Balance		8,559,477,000		6,994,460,000
Recorded Investment in Loans, Total		8,581,647,000		7,014,421,000
Non-accrual		15,298,000	[1]	20,090,000	[2]
Restructured		9,103,000	[1]	9,123,000	[2]
Total		24,401,000	[1]	29,213,000	[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		7,003,000		19,961,000
90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		15,167,000
Residential Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		7,347,000		7,892,000
Current Balance		2,867,667,000		2,585,684,000
Recorded Investment in Loans, Total		2,875,014,000		2,593,576,000
Non-accrual	[1]	352,000
Restructured		167,000	[1]	171,000	[2]
Total		519,000	[1]	171,000	[2]
Residential Real Estate [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		6,970,000		7,892,000
Residential Real Estate [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		377,000
Commercial And Industrial [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		14,656,000		11,883,000
Current Balance		3,289,578,000		2,426,055,000
Recorded Investment in Loans, Total		3,304,234,000		2,437,938,000
Non-accrual		14,741,000	[1]	19,904,000	[2]
Restructured		8,936,000	[1]	8,952,000	[2]
Total		23,677,000	[1]	28,856,000	[2]
Commercial And Industrial [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due				11,883,000
Commercial And Industrial [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		14,656,000
Securities-Based Loans [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Current Balance		1,786,966,000		1,819,206,000
Recorded Investment in Loans, Total		1,786,966,000		1,819,206,000
Commercial Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Current Balance		318,961,000		116,258,000
Recorded Investment in Loans, Total		318,961,000		116,258,000
Home Equity Lines Of Credit [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		33,000		184,000
Current Balance		38,065,000		14,855,000
Recorded Investment in Loans, Total		38,098,000		15,039,000
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		33,000		184,000
Construction And Land [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Current Balance		138,245,000		7,896,000
Recorded Investment in Loans, Total		138,245,000		7,896,000
Other [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		134,000		2,000
Current Balance		119,995,000		24,506,000
Recorded Investment in Loans, Total		120,129,000		24,508,000
Non-accrual		21,000	[1]	2,000	[2]
Total		21,000	[1]	2,000	[2]
Other [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due				$ 2,000
Other [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		$ 134,000

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

[2] There were no loans past due 90 days and still accruing interest at December 31, 2017.