Bank Loans (Recorded Balances Of Loans and Amount Of Allowance Allocated Based Upon Impairment Method by Portfolio Segment) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	$ 8,182	$ 8,182
Allowance for Loan Losses, Collectively Evaluated for Impairment	94,620	87,397
Allowance for Loan Losses, Total	102,802	95,579	$ 88,172	$ 85,833
Recorded Investment in Loans, Individually Evaluated for Impairment	14,351	14,587
Recorded Investment in Loans, Collectively Evaluated for Impairment	10,142,324	9,738,029
Recorded Investment in Loans, Total	10,156,675	9,752,616
Commercial And Industrial [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Individually Evaluated for Impairment	8,158	8,158
Allowance for Loan Losses, Collectively Evaluated for Impairment	51,804	61,791
Allowance for Loan Losses, Total	59,962	69,949	68,566	68,367
Recorded Investment in Loans, Individually Evaluated for Impairment	12,940	12,991
Recorded Investment in Loans, Collectively Evaluated for Impairment	3,800,922	3,425,962
Recorded Investment in Loans, Total	3,813,862	3,438,953
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	19,961	14,229
Allowance for Loan Losses, Total	19,985	14,253	11,585	11,228
Recorded Investment in Loans, Individually Evaluated for Impairment	1,411	1,412
Recorded Investment in Loans, Collectively Evaluated for Impairment	3,493,725	3,308,136
Recorded Investment in Loans, Total	3,495,136	3,309,548
Securities-Based Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment	2,915	2,361
Allowance for Loan Losses, Total	2,915	2,361	2,227	1,978
Recorded Investment in Loans, Collectively Evaluated for Impairment	1,945,371	2,098,211
Recorded Investment in Loans, Total	1,945,371	2,098,211
Commercial Real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment	8,165	3,564
Allowance for Loan Losses, Total	8,165	3,564	2,421	1,778
Recorded Investment in Loans, Collectively Evaluated for Impairment	399,732	428,549
Recorded Investment in Loans, Total	399,732	428,549
Construction And Land [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment	10,953	4,613
Allowance for Loan Losses, Total	10,953	4,613	1,724	1,241
Recorded Investment in Loans, Collectively Evaluated for Impairment	412,410	398,839
Recorded Investment in Loans, Total	412,410	398,839
Home Equity Lines Of Credit [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment	539	442
Allowance for Loan Losses, Total	539	442	372	310
Recorded Investment in Loans, Individually Evaluated for Impairment		184
Recorded Investment in Loans, Collectively Evaluated for Impairment	57,402	51,021
Recorded Investment in Loans, Total	57,402	51,205
Other [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment	283	194
Allowance for Loan Losses, Total	283	194	146	88
Recorded Investment in Loans, Collectively Evaluated for Impairment	32,762	27,311
Recorded Investment in Loans, Total	$ 32,762	27,311
Unallocated [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for Loan Losses, Collectively Evaluated for Impairment		203
Allowance for Loan Losses, Total		$ 203	$ 1,131	$ 843

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

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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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