Bank Loans (Aging of the Recorded Investment in Past Due Loans) (Details) - USD ($)		Jun. 30, 2024		Dec. 31, 2023
Financing Receivable Recorded Investment Past Due [Line Items]
Total		$ 19,554,758,000		$ 19,441,467,000
Non-accrual		70,791,000	[1]	42,366,000	[2]
Nonperforming loans with no allowance		14,312,000	[1]	3,090,000	[2]
Total		85,103,000	[1]	45,456,000	[2]
Loans past due 90 days and still accruing interest		0		0
Financial Asset, Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		49,435,000		22,043,000
30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		44,306,000		15,927,000
90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		5,129,000		6,116,000
Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		19,505,323,000		19,419,424,000
Residential Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		8,253,851,000		8,047,647,000
Non-accrual		1,435,000	[1]	3,090,000	[2]
Nonperforming loans with no allowance		924,000	[1]	1,000,000	[2]
Total		2,359,000	[1]	4,090,000	[2]
Residential Real Estate [Member] | Financial Asset, Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		18,468,000		19,257,000
Residential Real Estate [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		16,109,000		15,312,000
Residential Real Estate [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		2,359,000		3,945,000
Residential Real Estate [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		8,235,383,000		8,028,390,000
Commercial and Industrial [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		3,689,379,000		3,566,987,000
Non-accrual	[1]	33,266,000
Nonperforming loans with no allowance		13,388,000	[1]	2,022,000	[2]
Total		46,654,000	[1]	2,022,000	[2]
Commercial and Industrial [Member] | Financial Asset, Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		29,804,000		2,022,000
Commercial and Industrial [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		27,475,000
Commercial and Industrial [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		2,329,000		2,022,000
Commercial and Industrial [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		3,659,575,000		3,564,965,000
Fund Banking [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		3,346,785,000		3,633,126,000
Fund Banking [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		3,346,785,000		3,633,126,000
Securities-Based Loans [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		2,253,045,000		2,306,455,000
Nonperforming loans with no allowance	[2]			3,000
Total	[2]			3,000
Securities-Based Loans [Member] | Financial Asset, Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total				3,000
Securities-Based Loans [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total				3,000
Securities-Based Loans [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		2,253,045,000		2,306,452,000
Commercial Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		608,911,000		660,631,000
Non-accrual		35,649,000	[1]	39,195,000	[2]
Total		35,649,000	[1]	39,195,000	[2]
Commercial Real Estate [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		608,911,000		660,631,000
Construction And Land [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		1,198,395,000		1,034,370,000
Construction And Land [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		1,198,395,000		1,034,370,000
Home Equity Lines Of Credit [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		158,472,000		136,270,000
Non-accrual		378,000	[1]	22,000	[2]
Nonperforming loans with no allowance	[2]			65,000
Total		378,000	[1]	87,000	[2]
Home Equity Lines Of Credit [Member] | Financial Asset, Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		1,059,000		657,000
Home Equity Lines Of Credit [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		681,000		570,000
Home Equity Lines Of Credit [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		378,000		87,000
Home Equity Lines Of Credit [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		157,413,000		135,613,000
Other [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		45,920,000		55,981,000
Non-accrual		63,000	[1]	59,000	[2]
Total		63,000	[1]	59,000	[2]
Other [Member] | Financial Asset, Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		104,000		104,000
Other [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		41,000		45,000
Other [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		63,000		59,000
Other [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		$ 45,816,000		$ 55,877,000

[1] There were no loans past due 90 days and still accruing interest at June 30, 2024.

[2] There were no loans past due 90 days and still accruing interest at December 31, 2023. In the normal course of business, we may modify the original terms of a loan agreement. In certain circumstances, we may agree to modify the original terms of a loan agreement to a borrower experiencing financial difficulty, which may include a borrower in default, financial distress, bankruptcy or other circumstances. Modifications of loans to borrowers experiencing financial difficulty are designed to reduce our loss exposure while providing borrowers with an opportunity to work through financial difficulties, often to avoid foreclosure or bankruptcy. Loan modifications to borrowers experiencing financial difficulty typically involve principal forgiveness, an interest rate reduction, an other-than-insignificant payment delay (i.e., payment or maturity forbearance greater than six months), or a term extension, or any combination thereof. Modified loans to borrowers experiencing financial difficulty are subject to our nonaccrual policies. Loans to borrowers experiencing financial difficulty which were modified during the three and six months ended June 30, 2024 and 2023 were not significant. The gross interest income related to impaired loans, which would have been recorded, had these loans been current in accordance with their original terms, and the interest income recognized on these loans during the three and six months ended June 30, 2024 and 2023, were insignificant to the consolidated financial statements.