Bank Loans (Aging Of The Recorded Investment In Past Due Loans) (Details) - USD ($)		Jun. 30, 2016		Dec. 31, 2015		Jun. 30, 2015
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		$ 10,082,000		$ 4,116,000
Current Balance		4,203,981,000		3,176,468,000
Recorded Investment in Loans, Total		4,214,063,000		3,180,584,000		$ 2,475,815,000
Non-Accrual		34,919,000	[1]	737,000	[2]
Restructured		141,000	[1]	326,000	[2]
Total		35,060,000	[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		1,006,000		3,640,000
90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		9,076,000		476,000
Commercial And Industrial [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Current Balance		1,424,671,000		1,216,656,000
Recorded Investment in Loans, Total		1,424,671,000		1,216,656,000		1,010,810,000
Non-Accrual	[1]	25,381,000
Total	[1]	25,381,000
Securities Based Loans [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Current Balance		1,418,986,000		1,388,953,000
Recorded Investment in Loans, Total		1,418,986,000		1,388,953,000		963,090,000
Consumer [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		13,000		14,000
Current Balance		36,613,000		36,832,000
Recorded Investment in Loans, Total		36,626,000		36,846,000		20,269,000
Non-Accrual		17,000	[1]	15,000	[2]
Total		17,000	[1]	15,000	[2]
Consumer [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		3,000		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		1,159,000		3,760,000
Current Balance		1,227,075,000		425,372,000
Recorded Investment in Loans, Total		1,228,234,000		429,132,000		448,994,000
Non-Accrual		370,000	[1]	380,000	[2]
Restructured		141,000	[1]	326,000	[2]
Total		511,000	[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		921,000		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		238,000		450,000
Commercial Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		8,828,000
Current Balance		74,800,000		92,623,000
Recorded Investment in Loans, Total		83,628,000		92,623,000		20,053,000
Non-Accrual	[1]	8,828,000
Total	[1]	8,828,000
Commercial Real Estate [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		8,828,000
Home Equity Lines Of Credit [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total Past Due		82,000		342,000
Current Balance		14,074,000		12,133,000
Recorded Investment in Loans, Total		14,156,000		12,475,000		$ 12,599,000
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		82,000		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		7,762,000		3,899,000
Recorded Investment in Loans, Total		$ 7,762,000		$ 3,899,000

[1] There were no loans past due 90 days and still accruing interest at June 30, 2016.

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