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, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	$ 9,156		$ 9,105
Allowance for Loan Losses, Collectively Evaluated for Impairment	64,619		58,361
Allowance for Loan Losses, Total	73,775	$ 69,497	67,466	$ 54,202	$ 51,298	$ 45,163
Recorded Investment in Loans, Individually Evaluated for Impairment	24,084		29,213
Recorded Investment in Loans, Collectively Evaluated for Impairment	7,401,339		6,985,208
Recorded Investment in Loans, Total	7,425,423		7,014,421
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	9,304		8,406
Allowance for Loan Losses, Total	9,328	8,779	8,430	5,569	4,190	2,660
Recorded Investment in Loans, Individually Evaluated for Impairment	170		171
Recorded Investment in Loans, Collectively Evaluated for Impairment	2,703,765		2,593,405
Recorded Investment in Loans, Total	2,703,935		2,593,576
Commercial And Industrial [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	9,111		9,059
Allowance for Loan Losses, Collectively Evaluated for Impairment	50,461		45,415
Allowance for Loan Losses, Total	59,572	56,433	54,474	40,805	38,789	35,127
Recorded Investment in Loans, Individually Evaluated for Impairment	23,720		28,856
Recorded Investment in Loans, Collectively Evaluated for Impairment	2,653,376		2,409,082
Recorded Investment in Loans, Total	2,677,096		2,437,938
Securities-Based Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,928		2,088
Allowance for Loan Losses, Total	1,928	1,894	2,088	3,600	3,393	3,094
Recorded Investment in Loans, Collectively Evaluated for Impairment	1,845,592		1,819,206
Recorded Investment in Loans, Total	1,845,592		1,819,206
Commercial Real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment	1,672		1,520
Allowance for Loan Losses, Total	1,672	1,320	1,520	932	1,618	1,363
Recorded Investment in Loans, Collectively Evaluated for Impairment	127,253		116,258
Recorded Investment in Loans, Total	127,253		116,258
Consumer [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	1		2
Allowance for Loan Losses, Collectively Evaluated for Impairment	12		14
Allowance for Loan Losses, Total	13	15	16	105	107	129
Recorded Investment in Loans, Individually Evaluated for Impairment	1		2
Recorded Investment in Loans, Collectively Evaluated for Impairment	24,391		24,506
Recorded Investment in Loans, Total	24,392		24,508
Home Equity Lines Of Credit [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	20		20
Allowance for Loan Losses, Collectively Evaluated for Impairment	209		142
Allowance for Loan Losses, Total	229	164	162	283	285	371
Recorded Investment in Loans, Individually Evaluated for Impairment	193		184
Recorded Investment in Loans, Collectively Evaluated for Impairment	21,537		14,855
Recorded Investment in Loans, Total	21,730		15,039
Construction And Land [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment	303		100
Allowance for Loan Losses, Total	303	199	100	224	437	232
Recorded Investment in Loans, Collectively Evaluated for Impairment	25,425		7,896
Recorded Investment in Loans, Total	25,425		7,896
Qualitative [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment	730		676
Allowance for Loan Losses, Total	$ 730	$ 693	$ 676	$ 2,684	$ 2,479	$ 2,187