Bank Loans (Activity In The Allowance For Loan Losses By Portfolio Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning Balance	$ 54,202	$ 35,866	$ 45,163	$ 29,787
Provision	7,990	3,561	19,980	9,643
Charge-offs		(283)	(2,953)	(296)
Recoveries	37	1	39	11
Ending Balance	62,229	39,145	62,229	39,145
Commercial And Industrial [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning Balance	40,805	29,816	35,127	24,748
Provision	6,312	2,631	12,239	7,699
Charge-offs		(267)	(250)	(267)
Recoveries	35		36
Ending Balance	47,152	32,180	47,152	32,180
Securities-Based Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning Balance	3,600	1,731	3,094	1,607
Provision	(288)	172	218	296
Ending Balance	3,312	1,903	3,312	1,903
Consumer [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning Balance	105	107	129	105
Provision	(3)	203	(27)	205
Charge-offs		(16)		(16)
Recoveries	1	1	1	1
Ending Balance	103	295	103	295
Residential Real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning Balance	5,569	1,529	2,660	1,241
Provision	1,566	346	4,475	644
Charge-offs				(13)
Recoveries				3
Ending Balance	7,135	1,875	7,135	1,875
Commercial Real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning Balance	932	512	1,363	264
Provision	95	(8)	2,367	233
Charge-offs			(2,703)
Recoveries				7
Ending Balance	1,027	504	1,027	504
Home Equity Lines Of Credit [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning Balance	283	283	371	290
Provision	(13)	2	(102)	(5)
Recoveries	1		2
Ending Balance	271	285	271	285
Construction And Land [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning Balance	224	144	232	78
Provision	9	59	1	125
Ending Balance	233	203	233	203
Qualitative [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning Balance	2,684	1,744	2,187	1,454
Provision	312	156	809	446
Ending Balance	$ 2,996	$ 1,900	$ 2,996	$ 1,900