Bank Loans (Schedule Of Balance And Associated Percentage Of Each Major Loan Category In Bank Loan Portfolio) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross bank loans	$ 8,809,084	$ 8,581,647
Unamortized loan discount, net	(10,624)	(12,155)
Loans in process	(5,075)	27,984
Unamortized loan fees, net	1,476	5,972
Allowance for loan losses	(88,172)	(85,833)	$ (69,497)	$ (67,466)
Bank loans, net	$ 8,706,689	$ 8,517,615
Gross bank loans, Percent	100.00%	100.00%
Commercial And Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross bank loans	$ 3,314,564	$ 3,304,234
Allowance for loan losses	$ (68,566)	$ (68,367)	(56,433)	(54,474)
Gross bank loans, Percent	37.60%	38.50%
Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross bank loans	$ 2,928,228	$ 2,875,014
Allowance for loan losses	$ (11,585)	$ (11,228)	(8,779)	(8,430)
Gross bank loans, Percent	33.20%	33.50%
Securities-Based Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross bank loans	$ 1,860,989	$ 1,786,966
Allowance for loan losses	$ (2,227)	$ (1,978)	(1,894)	(2,088)
Gross bank loans, Percent	21.10%	20.80%
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross bank loans	$ 361,950	$ 318,961
Allowance for loan losses	$ (2,421)	$ (1,778)	(1,320)	(1,520)
Gross bank loans, Percent	4.10%	3.70%
Construction And Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross bank loans	$ 175,023	$ 138,245
Allowance for loan losses	$ (1,724)	$ (1,241)	(199)	(100)
Gross bank loans, Percent	2.00%	1.60%
Home Equity Lines Of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross bank loans	$ 44,235	$ 38,098
Allowance for loan losses	$ (372)	$ (310)	(164)	(162)
Gross bank loans, Percent	0.50%	0.40%
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross bank loans	$ 124,095	$ 120,129
Allowance for loan losses	$ (146)	$ (88)	$ (15)	$ (16)
Gross bank loans, Percent	1.50%	1.50%

Loans and leases payable receivable loans in process.

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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 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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