Bank Loans (Schedule of Term Loans Amortized Cost Basis by Origination Year and Revolving Cost Amortized Cost Basis) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	$ 12,898,807	$ 11,170,813
Commercial And Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	4,950,516	4,296,089
Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	712,522
Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	468,096
Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	462,634
Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	878,669
Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	414,742
Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	440,474
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	1,573,379
Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	4,567,467	3,956,670
Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,204,294
Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,459,836
Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	736,759
Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	302,347
Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	242,861
Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	621,370
Securities-Based Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	2,331,737	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	6,190
Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	39,609
Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	93,677
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	22,985
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	2,168,842
Construction And Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	563,552	501,681
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	27,356
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	79,439
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	223,544
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	163,809
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	63,104
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	6,300
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	370,517	366,485
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	63,076
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	72,954
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	151,371
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	22,478
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	30,105
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	30,533
Home Equity Lines Of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	76,839	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	76,839
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	38,179	40,407
Other [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	157
Other [Member] | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	38,022
Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	12,586,626	10,824,109
Pass [Member] | Commercial And Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	4,708,163	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	712,522
Pass [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	467,589
Pass [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	408,459
Pass [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	790,870
Pass [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	350,147
Pass [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	406,331
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	1,572,245
Pass [Member] | Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	4,562,689	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	1,204,294
Pass [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,457,540
Pass [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	736,759
Pass [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	301,660
Pass [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	242,712
Pass [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	619,724
Pass [Member] | Securities-Based Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	2,331,737	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	6,190
Pass [Member] | Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	39,609
Pass [Member] | Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	93,677
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	22,985
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	2,168,842
Pass [Member] | Construction And Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	529,312	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	27,356
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	79,439
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	223,544
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	129,569
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	63,104
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	6,300
Pass [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	339,707	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	63,076
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	50,535
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	151,371
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	22,442
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	30,105
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	22,178
Pass [Member] | Home Equity Lines Of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	76,839	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	76,839
Pass [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	38,179	40,407
Pass [Member] | Other [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	157
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	38,022
Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	107,046	130,332
Special Mention [Member] | Commercial And Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	68,006	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	41,580
Special Mention [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	26,426
Special Mention [Member] | Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	2,381
Special Mention [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	2,296
Special Mention [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	85
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	22,419	10,333
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	22,419
Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	196,754	202,728
Substandard [Member] | Commercial And Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	167,251	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	507
Substandard [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	54,175
Substandard [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	46,219
Substandard [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	57,509
Substandard [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	7,707
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	1,134
Substandard [Member] | Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,148
Substandard [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	687
Substandard [Member] | Residential Mortgage | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	461
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	8,355
Substandard [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	8,355
Doubtful [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	8,381	13,644
Doubtful [Member] | Commercial And Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	7,096	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	7,086
Doubtful [Member] | Commercial And Industrial | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	10
Doubtful [Member] | Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,249	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	36	$ 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	$ 36