Bank Loans (Schedule of Term Loans Amortized Cost Basis by Origination Year and Revolving Cost Amortized Cost Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	$ 11,170,813	$ 9,752,616
Commercial And Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	4,296,089	3,438,953
Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	847,993
Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	554,734
Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	844,843
Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	451,578
Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	212,146
Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	301,502
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	1,083,293
Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	3,956,670	3,309,548
Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,600,107
Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	896,190
Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	375,252
Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	302,673
Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	272,101
Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	510,347
Securities-Based Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,933,974	2,098,211
Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	25,563
Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	104,011
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] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	300
Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	16,716
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	1,786,950
Construction And Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	501,681	398,839
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	68,392
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	206,085
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	153,656
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	61,289
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	6,450
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,355
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	4,454
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	366,485	428,549
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	77,792
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	151,805
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	38,888
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	45,275
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	14,340
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	37,903
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	482
Home Equity Lines Of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	75,507	51,205
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	75,507
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	40,407	27,311
Other [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	5
Other [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	503
Other [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	197
Other [Member] | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	39,702
Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	10,824,109	9,676,864
Pass [Member] | Commercial And Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	3,995,351	3,365,800
Pass [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	828,098
Pass [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	519,723
Pass [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	743,440
Pass [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	332,986
Pass [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	204,369
Pass [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	297,288
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	1,069,447
Pass [Member] | Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	3,955,421	3,307,719
Pass [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,600,107
Pass [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	896,190
Pass [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	375,252
Pass [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	302,524
Pass [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	272,101
Pass [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	509,247
Pass [Member] | Securities-Based Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,933,974	2,098,211
Pass [Member] | Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	25,563
Pass [Member] | Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	104,011
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] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	300
Pass [Member] | Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	16,716
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	1,786,950
Pass [Member] | Construction And Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	467,441	398,839
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	68,392
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	206,085
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	119,416
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	61,289
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	6,450
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,355
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	4,454
Pass [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	356,008	427,963
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	77,792
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	151,805
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	38,744
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	45,275
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	4,007
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	37,903
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	482
Pass [Member] | Home Equity Lines Of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	75,507	51,021
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	75,507
Pass [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	40,407	27,311
Pass [Member] | Other [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	5
Pass [Member] | Other [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	503
Pass [Member] | Other [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	197
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	39,702
Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	202,728	13,568
Substandard [Member] | Commercial And Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	182,728	11,972
Substandard [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	19,395
Substandard [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	34,772
Substandard [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	65,801
Substandard [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	48,647
Substandard [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	7,777
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	6,336
Substandard [Member] | Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year		1,412
Substandard [Member] | Construction And Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	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] | Home Equity Lines Of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year		184
Doubtful [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	13,644	12,940
Doubtful [Member] | Commercial And Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	12,251	12,940
Doubtful [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	12,237
Doubtful [Member] | Commercial And Industrial | Prior [Member]
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	1,249
Doubtful [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	149
Doubtful [Member] | Residential Mortgage | Prior [Member]
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
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
Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	130,332	49,244
Special Mention [Member] | Commercial And Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	105,759	48,241
Special Mention [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	500
Special Mention [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	239
Special Mention [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	35,602
Special Mention [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	57,708
Special Mention [Member] | Commercial And Industrial | Prior [Member]
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	7,510
Special Mention [Member] | Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year		417
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
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	10,333	$ 586
Special Mention [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	$ 10,333