Bank Loans (Risk Category Of Loan Portfolio) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	$ 12,215,192	$ 11,170,813
Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	11,853,896	10,824,109
Special Mention [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	185,216	130,332
Substandard [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	162,603	202,728
Doubtful [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	13,477	13,644
Commercial And Industrial
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	4,923,494	4,296,089
Commercial And Industrial | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	4,607,280	3,995,351
Commercial And Industrial | Special Mention [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	164,839	105,759
Commercial And Industrial | Substandard [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	139,967	182,728
Commercial And Industrial | Doubtful [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	11,408	12,251
Residential Mortgage
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	4,158,033	3,956,670
Residential Mortgage | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	4,155,773	3,955,421
Residential Mortgage | Special Mention [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	335
Residential Mortgage | Doubtful [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	1,925	1,249
Securities-Based Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	2,089,747	1,933,974
Securities-Based Loans [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	2,089,747	1,933,974
Commercial Real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	374,736	366,485
Commercial Real Estate [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	366,154	356,008
Commercial Real Estate [Member] | Special Mention [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	5,802	10,333
Commercial Real Estate [Member] | Substandard [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	2,636
Commercial Real Estate [Member] | Doubtful [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	144	144
Construction And Land [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	560,191	501,681
Construction And Land [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	525,951	467,441
Construction And Land [Member] | Special Mention [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	14,240	14,240
Construction And Land [Member] | Substandard [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	20,000	20,000
Home Equity Lines Of Credit [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	71,172	75,507
Home Equity Lines Of Credit [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	71,172	75,507
Other [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	37,819	40,407
Other [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
Total risk category of loan portfolio	$ 37,819	$ 40,407