Bank Loans (Schedule Of Balance And Associated Percentage Of Each Major Loan Category In Bank Loan Portfolio) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross bank loans	$ 7,154,661	$ 7,014,421
Unamortized loan premium, net	362	788
Loans in process	(10,928)	(856)
Unamortized loan fees, net	1,684	872
Allowance for loan losses	(69,497)	(67,466)	$ (51,298)	$ (45,163)
Bank loans, net	$ 7,076,282	$ 6,947,759
Gross bank loans, Percent	100.00%	100.00%
Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross bank loans	$ 2,634,069	$ 2,593,576
Allowance for loan losses	$ (8,779)	$ (8,430)	(4,190)	(2,660)
Gross bank loans, Percent	36.80%	37.00%
Commercial And Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross bank loans	$ 2,553,671	$ 2,437,938
Allowance for loan losses	$ (56,433)	$ (54,474)	(38,789)	(35,127)
Gross bank loans, Percent	35.70%	34.80%
Securities-Based Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross bank loans	$ 1,809,281	$ 1,819,206
Allowance for loan losses	$ (1,894)	$ (2,088)	(3,393)	(3,094)
Gross bank loans, Percent	25.30%	25.90%
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross bank loans	$ 101,591	$ 116,258
Allowance for loan losses	$ (1,320)	$ (1,520)	(1,618)	(1,363)
Gross bank loans, Percent	1.40%	1.70%
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross bank loans	$ 24,699	$ 24,508
Allowance for loan losses	$ (15)	$ (16)	(107)	(129)
Gross bank loans, Percent	0.30%	0.30%
Home Equity Lines Of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross bank loans	$ 15,013	$ 15,039
Allowance for loan losses	$ (164)	$ (162)	(285)	(371)
Gross bank loans, Percent	0.20%	0.20%
Construction And Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross bank loans	$ 16,337	$ 7,896
Allowance for loan losses	$ (199)	$ (100)	$ (437)	$ (232)
Gross bank loans, Percent	0.30%	0.10%

Percentage of loans and leases receivable gross carrying amount.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount of deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount of undisbursed portion of the loan receivable balance (loans in process). Excludes loans and leases covered under loss sharing agreements.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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Amount of deferred fees paid by borrowers and unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of loans that are being amortized into income as an adjustment to yield. Excludes amounts for loans and leases covered under loss sharing agreements.

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