Bank Loans (Schedule of Term Loans Amortized Cost Basis by Origination Year and Revolving Cost Amortized Cost Basis) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	$ 12,215,192	$ 11,170,813
Commercial And Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	4,923,494	4,296,089
Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	852,103
Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	495,250
Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	581,366
Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	805,525
Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	423,087
Commercial And Industrial | Term Loans Amortized Cost Basis By Origination Year Prior To Two Thousand Sixteen
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	514,061
Commercial And Industrial | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,252,102
Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	4,158,033	3,956,670
Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	485,925
Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,548,638
Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	815,040
Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	340,371
Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	272,633
Residential Mortgage | Term Loans Amortized Cost Basis By Origination Year Prior To Two Thousand Sixteen
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	695,426
Securities-Based Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	2,089,747	1,933,974
Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	973
Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	38,702
Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	102,973
Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	294
Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	140
Securities-Based Loans [Member] | Term Loans Amortized Cost Basis By Origination Year Prior To Two Thousand Sixteen
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	16,906
Securities-Based Loans [Member] | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,929,759
Construction And Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	560,191	501,681
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	13,842
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	87,316
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	218,904
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	162,419
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	62,248
Construction And Land [Member] | Term Loans Amortized Cost Basis By Origination Year Prior To Two Thousand Sixteen
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	6,401
Construction And Land [Member] | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	9,061
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	374,736	366,485
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	22,047
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	81,378
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	152,732
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	25,472
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	38,352
Commercial Real Estate [Member] | Term Loans Amortized Cost Basis By Origination Year Prior To Two Thousand Sixteen
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	54,413
Commercial Real Estate [Member] | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	342
Home Equity Lines Of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	71,172	75,507
Home Equity Lines Of Credit [Member] | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	71,172
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	37,819	40,407
Other [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	4
Other [Member] | Term Loans Amortized Cost Basis By Origination Year Prior To Two Thousand Sixteen
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	445
Other [Member] | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	37,370
Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	11,853,896	10,824,109
Pass [Member] | Commercial And Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	4,607,280	3,995,351
Pass [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	852,103
Pass [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	494,747
Pass [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	527,136
Pass [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	679,772
Pass [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	302,188
Pass [Member] | Commercial And Industrial | Term Loans Amortized Cost Basis By Origination Year Prior To Two Thousand Sixteen
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	502,085
Pass [Member] | Commercial And Industrial | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,249,249
Pass [Member] | Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	4,155,773	3,955,421
Pass [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	485,925
Pass [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,548,638
Pass [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	815,040
Pass [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	340,371
Pass [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	271,808
Pass [Member] | Residential Mortgage | Term Loans Amortized Cost Basis By Origination Year Prior To Two Thousand Sixteen
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	693,991
Pass [Member] | Securities-Based Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	2,089,747	1,933,974
Pass [Member] | Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	973
Pass [Member] | Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	38,702
Pass [Member] | Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	102,973
Pass [Member] | Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	294
Pass [Member] | Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	140
Pass [Member] | Securities-Based Loans [Member] | Term Loans Amortized Cost Basis By Origination Year Prior To Two Thousand Sixteen
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	16,906
Pass [Member] | Securities-Based Loans [Member] | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,929,759
Pass [Member] | Construction And Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	525,951	467,441
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	13,842
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	87,316
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	218,904
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	128,179
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	62,248
Pass [Member] | Construction And Land [Member] | Term Loans Amortized Cost Basis By Origination Year Prior To Two Thousand Sixteen
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	6,401
Pass [Member] | Construction And Land [Member] | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	9,061
Pass [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	366,154	356,008
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	22,047
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	81,378
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	152,732
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	25,328
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	38,352
Pass [Member] | Commercial Real Estate [Member] | Term Loans Amortized Cost Basis By Origination Year Prior To Two Thousand Sixteen
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	45,975
Pass [Member] | Commercial Real Estate [Member] | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	342
Pass [Member] | Home Equity Lines Of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	71,172	75,507
Pass [Member] | Home Equity Lines Of Credit [Member] | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	71,172
Pass [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	37,819	40,407
Pass [Member] | Other [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	4
Pass [Member] | Other [Member] | Term Loans Amortized Cost Basis By Origination Year Prior To Two Thousand Sixteen
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	445
Pass [Member] | Other [Member] | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	37,370
Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	185,216	130,332
Special Mention [Member] | Commercial And Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	164,839	105,759
Special Mention [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	503
Special Mention [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	30,309
Special Mention [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	82,558
Special Mention [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	45,947
Special Mention [Member] | Commercial And Industrial | Term Loans Amortized Cost Basis By Origination Year Prior To Two Thousand Sixteen
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	4,200
Special Mention [Member] | Commercial And Industrial | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,322
Special Mention [Member] | Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	335
Special Mention [Member] | Residential Mortgage | Term Loans Amortized Cost Basis By Origination Year Prior To Two Thousand Sixteen
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	335
Special Mention [Member] | Construction And Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	14,240	14,240
Special Mention [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	14,240
Special Mention [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	5,802	10,333
Special Mention [Member] | Commercial Real Estate [Member] | Term Loans Amortized Cost Basis By Origination Year Prior To Two Thousand Sixteen
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	5,802
Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	162,603	202,728
Substandard [Member] | Commercial And Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	139,967	182,728
Substandard [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	23,921
Substandard [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	43,195
Substandard [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	63,558
Substandard [Member] | Commercial And Industrial | Term Loans Amortized Cost Basis By Origination Year Prior To Two Thousand Sixteen
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	7,762
Substandard [Member] | Commercial And Industrial | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,531
Substandard [Member] | Construction And Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	20,000	20,000
Substandard [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	20,000
Substandard [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	2,636
Substandard [Member] | Commercial Real Estate [Member] | Term Loans Amortized Cost Basis By Origination Year Prior To Two Thousand Sixteen
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	2,636
Doubtful [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	13,477	13,644
Doubtful [Member] | Commercial And Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	11,408	12,251
Doubtful [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	11,394
Doubtful [Member] | Commercial And Industrial | Term Loans Amortized Cost Basis By Origination Year Prior To Two Thousand Sixteen
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	14
Doubtful [Member] | Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,925	1,249
Doubtful [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	825
Doubtful [Member] | Residential Mortgage | Term Loans Amortized Cost Basis By Origination Year Prior To Two Thousand Sixteen
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,100
Doubtful [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	144	$ 144
Doubtful [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	$ 144