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

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The balance of financing receivables that were individually 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	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	$ 8,348		$ 8,703
Allowance for Loan Losses, Collectively Evaluated for Impairment	82,124		77,130
Allowance for Loan Losses, Total	90,472	$ 88,172	85,833	$ 73,775	$ 69,497	$ 67,466
Recorded Investment in Loans, Individually Evaluated for Impairment	23,465		24,401
Recorded Investment in Loans, Collectively Evaluated for Impairment	9,042,813		8,557,246
Recorded Investment in Loans, Total	9,066,278		8,581,647
Commercial And Industrial [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	8,304		8,678
Allowance for Loan Losses, Collectively Evaluated for Impairment	60,959		59,689
Allowance for Loan Losses, Total	69,263	68,566	68,367	59,572	56,433	54,474
Recorded Investment in Loans, Individually Evaluated for Impairment	21,995		23,677
Recorded Investment in Loans, Collectively Evaluated for Impairment	3,316,132		3,280,557
Recorded Investment in Loans, Total	3,338,127		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	12,018		11,204
Allowance for Loan Losses, Total	12,042	11,585	11,228	9,328	8,779	8,430
Recorded Investment in Loans, Individually Evaluated for Impairment	1,121		519
Recorded Investment in Loans, Collectively Evaluated for Impairment	2,983,604		2,874,495
Recorded Investment in Loans, Total	2,984,725		2,875,014
Securities-Based Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment	2,311		1,978
Allowance for Loan Losses, Total	2,311	2,227	1,978	1,928	1,894	2,088
Recorded Investment in Loans, Collectively Evaluated for Impairment	1,962,528		1,786,966
Recorded Investment in Loans, Total	1,962,528		1,786,966
Commercial Real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment	2,478		1,778
Allowance for Loan Losses, Total	2,478	2,421	1,778	1,672	1,320	1,520
Recorded Investment in Loans, Collectively Evaluated for Impairment	367,283		318,961
Recorded Investment in Loans, Total	367,283		318,961
Construction And Land [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment	2,402		1,241
Allowance for Loan Losses, Total	2,402	1,724	1,241	303	199	100
Recorded Investment in Loans, Collectively Evaluated for Impairment	226,559		138,245
Recorded Investment in Loans, Total	226,559		138,245
Home Equity Lines Of Credit [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment	421		310
Allowance for Loan Losses, Total	421	372	310	229	164	162
Recorded Investment in Loans, Individually Evaluated for Impairment	184		184
Recorded Investment in Loans, Collectively Evaluated for Impairment	49,025		37,914
Recorded Investment in Loans, Total	49,209		38,098
Other [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	20		1
Allowance for Loan Losses, Collectively Evaluated for Impairment	159		87
Allowance for Loan Losses, Total	179	146	88	13	15	16
Recorded Investment in Loans, Individually Evaluated for Impairment	165		21
Recorded Investment in Loans, Collectively Evaluated for Impairment	137,682		120,108
Recorded Investment in Loans, Total	137,847		120,129
Qualitative [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,376		843
Allowance for Loan Losses, Total	$ 1,376	$ 1,131	$ 843	$ 730	$ 693	$ 676