Bank Loans (Schedule of Term Loans Amortized Cost Basis by Origination Year and Revolving Cost Amortized Cost Basis) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	$ 10,574,297	$ 9,752,616
Commercial And Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	4,149,307	3,438,953
Commercial And Industrial [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	368,449
Commercial And Industrial [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	68,674
Commercial And Industrial [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	2,621,440
Commercial And Industrial [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	21,639
Commercial And Industrial [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	21,647
Commercial And Industrial [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	35,124
Commercial And Industrial [Member] | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,012,334
Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	3,710,657	3,309,548
Residential Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	893,802
Residential Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,037,080
Residential Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	444,563
Residential Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	355,567
Residential Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	324,468
Residential Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	655,177
Securities-Based Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,716,786	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	15,217
Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	102,590
Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,614
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	22,993
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	1,573,932
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	406,788	428,549
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	74,126
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	154,844
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	44,416
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	54,879
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	20,348
Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	57,186
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	989
Construction And Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	472,216	398,839
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	25,968
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	205,501
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	157,524
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	65,126
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	7,484
Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,542
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	9,071
Home Equity Lines Of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	62,699	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	62,699
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	55,844	27,311
Other [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	6
Other [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,006
Other [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	51
Other [Member] | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	54,781
Pass [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	10,314,588	9,676,864
Pass [Member] | Commercial And Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	3,926,827	3,365,800
Pass [Member] | Commercial And Industrial [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	368,449
Pass [Member] | Commercial And Industrial [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	68,674
Pass [Member] | Commercial And Industrial [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	2,422,517
Pass [Member] | Commercial And Industrial [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	8,699
Pass [Member] | Commercial And Industrial [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	21,647
Pass [Member] | Commercial And Industrial [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	35,096
Pass [Member] | Commercial And Industrial [Member] | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,001,745
Pass [Member] | Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	3,709,274	3,307,719
Pass [Member] | Residential Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	893,802
Pass [Member] | Residential Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,037,080
Pass [Member] | Residential Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	444,563
Pass [Member] | Residential Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	355,418
Pass [Member] | Residential Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	324,468
Pass [Member] | Residential Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	653,943
Pass [Member] | Securities-Based Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,716,786	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	15,217
Pass [Member] | Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	102,590
Pass [Member] | Securities-Based Loans [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,614
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	22,993
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	1,573,932
Pass [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	405,471	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	74,126
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	154,844
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	44,272
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	54,879
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	19,175
Pass [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	57,186
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	989
Pass [Member] | Construction And Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	438,555	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	25,968
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	205,501
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	123,863
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	65,126
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	7,484
Pass [Member] | Construction And Land [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,542
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	9,071
Pass [Member] | Home Equity Lines Of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	61,831	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	61,831
Pass [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	55,844	27,311
Pass [Member] | Other [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	6
Pass [Member] | Other [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,006
Pass [Member] | Other [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	51
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	54,781
Special Mention [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	194,349	49,244
Special Mention [Member] | Commercial And Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	158,513	48,241
Special Mention [Member] | Commercial And Industrial [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	156,946
Special Mention [Member] | Commercial And Industrial [Member] | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,567
Special Mention [Member] | Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	134	417
Special Mention [Member] | Residential Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	134
Special Mention [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,173	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	1,173
Special Mention [Member] | Construction And Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	33,661
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	33,661
Special Mention [Member] | Home Equity Lines Of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	868
Special Mention [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	868
Substandard [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	51,171	13,568
Substandard [Member] | Commercial And Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	51,027	11,972
Substandard [Member] | Commercial And Industrial [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	41,977
Substandard [Member] | Commercial And Industrial [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	28
Substandard [Member] | Commercial And Industrial [Member] | Revolving Loans Amortized Cost Basis [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	9,022
Substandard [Member] | Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year		1,412
Substandard [Member] | Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	144
Substandard [Member] | Commercial Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	144
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	14,189	12,940
Doubtful [Member] | Commercial And Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	12,940	$ 12,940
Doubtful [Member] | Commercial And Industrial [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	12,940
Doubtful [Member] | Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	1,249
Doubtful [Member] | Residential Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	149
Doubtful [Member] | Residential Real Estate [Member] | Prior [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loans amortized cost basis by origination year	$ 1,100