The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Bank Loans (Recorded Balances Of Loans and Amount Of Allowance Allocated Based Upon Impairment Method by Portfolio Segment) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	$ 8,200		$ 8,703
Allowance for Loan Losses, Collectively Evaluated for Impairment	83,160		77,130
Allowance for Loan Losses, Total	91,360	$ 90,472	85,833	$ 80,700	$ 73,775	$ 67,466
Recorded Investment in Loans, Individually Evaluated for Impairment	16,203		24,401
Recorded Investment in Loans, Collectively Evaluated for Impairment	9,181,429		8,557,246
Recorded Investment in Loans, Total	9,197,632		8,581,647
Commercial And Industrial [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	8,158		8,678
Allowance for Loan Losses, Collectively Evaluated for Impairment	60,014		59,689
Allowance for Loan Losses, Total	68,172	69,263	68,367	64,580	59,572	54,474
Recorded Investment in Loans, Individually Evaluated for Impairment	14,169		23,677
Recorded Investment in Loans, Collectively Evaluated for Impairment	3,301,537		3,280,557
Recorded Investment in Loans, Total	3,315,706		3,304,234
Residential Real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	24		24
Allowance for Loan Losses, Collectively Evaluated for Impairment	12,538		11,204
Allowance for Loan Losses, Total	12,562	12,042	11,228	10,493	9,328	8,430
Recorded Investment in Loans, Individually Evaluated for Impairment	1,697		519
Recorded Investment in Loans, Collectively Evaluated for Impairment	3,041,574		2,874,495
Recorded Investment in Loans, Total	3,043,271		2,875,014
Securities-Based Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment	2,181		1,978
Allowance for Loan Losses, Total	2,181	2,311	1,978	1,923	1,928	2,088
Recorded Investment in Loans, Collectively Evaluated for Impairment	1,986,339		1,786,966
Recorded Investment in Loans, Total	1,986,339		1,786,966
Commercial Real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment	2,903		1,778
Allowance for Loan Losses, Total	2,903	2,478	1,778	1,762	1,672	1,520
Recorded Investment in Loans, Collectively Evaluated for Impairment	387,868		318,961
Recorded Investment in Loans, Total	387,868		318,961
Construction And Land [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment	3,267		1,241
Allowance for Loan Losses, Total	3,267	2,402	1,241	903	303	100
Recorded Investment in Loans, Collectively Evaluated for Impairment	293,116		138,245
Recorded Investment in Loans, Total	293,116		138,245
Home Equity Lines Of Credit [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment	435		310
Allowance for Loan Losses, Total	435	421	310	229	229	162
Recorded Investment in Loans, Individually Evaluated for Impairment	184		184
Recorded Investment in Loans, Collectively Evaluated for Impairment	50,334		37,914
Recorded Investment in Loans, Total	50,518		38,098
Other [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	18		1
Allowance for Loan Losses, Collectively Evaluated for Impairment	177		87
Allowance for Loan Losses, Total	195	179	88	11	13	16
Recorded Investment in Loans, Individually Evaluated for Impairment	153		21
Recorded Investment in Loans, Collectively Evaluated for Impairment	120,661		120,108
Recorded Investment in Loans, Total	120,814		120,129
Qualitative [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,645		843
Allowance for Loan Losses, Total	$ 1,645	$ 1,376	$ 843	$ 799	$ 730	$ 676