Bank Loans (Aging Of The Recorded Investment In Past Due Loans) (Details) - USD ($)		Mar. 31, 2016		Dec. 31, 2015
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		$ 2,040,000		$ 4,116,000
Current Balance		3,503,469,000		3,176,468,000
Recorded Investment in Loans, Total		3,505,509,000		3,180,584,000
Non-Accrual		22,678,000	[1]	737,000	[2]
Restructured		324,000	[1]	326,000	[2]
Total		23,002,000	[1]	1,063,000	[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		1,580,000		3,640,000
90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		460,000		476,000
Commercial And Industrial [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Current Balance		1,295,318,000		1,216,656,000
Recorded Investment in Loans, Total		1,295,318,000		1,216,656,000
Non-Accrual	[1]	12,148,000
Total	[1]	12,148,000
Securities Based Loans [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Current Balance		1,345,719,000		1,388,953,000
Recorded Investment in Loans, Total		1,345,719,000		1,388,953,000
Consumer [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		15,000		14,000
Current Balance		31,021,000		36,832,000
Recorded Investment in Loans, Total		31,036,000		36,846,000
Non-Accrual		18,000	[1]	15,000	[2]
Total		18,000	[1]	15,000	[2]
Consumer [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		5,000		7,000
Consumer [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		10,000		7,000
Residential Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		1,977,000		3,760,000
Current Balance		728,706,000		425,372,000
Recorded Investment in Loans, Total		730,683,000		429,132,000
Non-Accrual		380,000	[1]	380,000	[2]
Restructured		324,000	[1]	326,000	[2]
Total		704,000	[1]	706,000	[2]
Residential Real Estate [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		1,527,000		3,310,000
Residential Real Estate [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		450,000		450,000
Commercial Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Current Balance		83,273,000		92,623,000
Recorded Investment in Loans, Total		83,273,000		92,623,000
Non-Accrual	[1]	9,809,000
Total	[1]	9,809,000
Home Equity Lines Of Credit [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		48,000		342,000
Current Balance		12,463,000		12,133,000
Recorded Investment in Loans, Total		12,511,000		12,475,000
Non-Accrual		323,000	[1]	342,000	[2]
Total		323,000	[1]	342,000	[2]
Home Equity Lines Of Credit [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		48,000		323,000
Home Equity Lines Of Credit [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due				19,000
Construction And Land [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Current Balance		6,969,000		3,899,000
Recorded Investment in Loans, Total		$ 6,969,000		$ 3,899,000

[1] There were no loans past due 90 days and still accruing interest at March 31, 2016.

[2] There were no loans past due 90 days and still accruing interest at December 31, 2015.