Bank Loans (Aging of the Recorded Investment in Past Due Loans) (Details) - USD ($)		Sep. 30, 2024		Dec. 31, 2023
Financing Receivable Recorded Investment Past Due [Line Items]
Total		$ 20,349,581,000		$ 19,441,467,000
Non-accrual		128,584,000	[1]	42,366,000	[2]
Nonperforming loans with no allowance		15,538,000	[1]	3,090,000	[2]
Total		144,122,000	[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		78,556,000		22,043,000
30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		73,861,000		15,927,000
90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		4,695,000		6,116,000
Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		20,271,025,000		19,419,424,000
Residential Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		8,406,932,000		8,047,647,000
Non-accrual		1,251,000	[1]	3,090,000	[2]
Nonperforming loans with no allowance		1,705,000	[1]	1,000,000	[2]
Total		2,956,000	[1]	4,090,000	[2]
Residential Real Estate [Member] | Financial Asset, Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		15,823,000		19,257,000
Residential Real Estate [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		12,597,000		15,312,000
Residential Real Estate [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		3,226,000		3,945,000
Residential Real Estate [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		8,391,109,000		8,028,390,000
Commercial and Industrial [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		3,896,824,000		3,566,987,000
Non-accrual	[1]	34,813,000
Nonperforming loans with no allowance		13,833,000	[1]	2,022,000	[2]
Total		57,575,000	[1]	2,022,000	[2]
Commercial and Industrial [Member] | Financial Asset, Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		60,901,000		2,022,000
Commercial and Industrial [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		60,901,000
Commercial and Industrial [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total				2,022,000
Commercial and Industrial [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		3,835,923,000		3,564,965,000
Fund Banking [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		3,762,960,000		3,633,126,000
Fund Banking [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		3,762,960,000		3,633,126,000
Securities-Based Loans [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		2,273,246,000		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		850,000		3,000
Securities-Based Loans [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		850,000		3,000
Securities-Based Loans [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		2,272,396,000		2,306,452,000
Commercial Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		565,686,000		660,631,000
Non-accrual		43,742,000	[1]	39,195,000	[2]
Total		34,813,000	[1]	39,195,000	[2]
Commercial Real Estate [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		565,686,000		660,631,000
Construction And Land [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		1,219,787,000		1,034,370,000
Non-accrual	[1]	48,349,000
Total	[1]	48,349,000
Construction And Land [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		1,219,787,000		1,034,370,000
Home Equity Lines Of Credit [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		170,732,000		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		873,000		657,000
Home Equity Lines Of Credit [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		305,000		570,000
Home Equity Lines Of Credit [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		568,000		87,000
Home Equity Lines Of Credit [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		169,859,000		135,613,000
Other [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		53,414,000		55,981,000
Non-accrual		51,000	[1]	59,000	[2]
Total		51,000	[1]	59,000	[2]
Other [Member] | Financial Asset, Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		109,000		104,000
Other [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		58,000		45,000
Other [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		51,000		59,000
Other [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		$ 53,305,000		$ 55,877,000

[1] There were no loans past due 90 days and still accruing interest at September 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 nine months ended September 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 nine months ended September 30, 2024 and 2023, were insignificant to the consolidated financial statements. Credit quality indicators As of September 30, 2024, bank loans were primarily extended to non-investment grade borrowers. Substantially all of these loans align with the U.S. Federal bank regulatory agencies’ definition of Pass. Loans meet the definition of Pass when they are performing and do not demonstrate adverse characteristics that are likely to result in a credit loss. A loan is determined to be impaired when principal or interest becomes 90 days past due or when collection becomes uncertain. At the time a loan is determined to be impaired, the accrual of interest and amortization of deferred loan origination fees is discontinued (“nonaccrual status”), and any accrued and unpaid interest income is reversed. We closely monitor economic conditions and loan performance trends to manage and evaluate our exposure to credit risk. Trends in delinquency ratios are an indicator, among other considerations, of credit risk within our loan portfolio. The level of nonperforming assets represents another indicator of the potential for future credit losses. Accordingly, key metrics we track and use in evaluating the credit quality of our loan portfolio include delinquency and nonperforming asset rates, as well as charge-off rates and our internal risk ratings of the loan portfolio. In general, we are a secured lender. At September 30, 2024 and December 31, 2023, 96.8% and 97.0% of our loan portfolio was collateralized, respectively. Collateral is required in accordance with the normal credit evaluation process based upon the creditworthiness of the customer and the credit risk associated with the particular transaction. The Company uses the following definitions for risk ratings: Pass. A credit exposure rated pass has a continued expectation of timely repayment, all obligations of the borrower are current, and the obligor complies with material terms and conditions of the lending agreement. Special Mention. Extensions of credit that have potential weakness that deserve management’s close attention, and if left uncorrected may, at some future date, result in the deterioration of the repayment prospects or collateral position. Substandard. Obligor has a well-defined weakness that jeopardizes the repayment of the debt and has a high probability of payment default with the distinct possibility that the Company will sustain some loss if noted deficiencies are not corrected. Doubtful. Inherent weakness in the exposure makes the collection or repayment in full, based on existing facts, conditions and circumstances, highly improbable, and the amount of loss is uncertain. Substandard loans are regularly reviewed for impairment. Doubtful loans are considered impaired. When a loan is impaired the impairment is measured based on the present value of expected future cash flows discounted at the loan’s effective interest rate, or as a practical expedient, the observable market price of the loan or the fair value of the collateral if the loan is collateral dependent. Based on the most recent analysis performed, the risk category of our loan portfolio was as follows (in thousands):     As of September 30, 2024       Pass     Special Mention     Substandard     Doubtful     Total   Residential real estate   $ 8,401,700     $ 2,006     $ 3,226     $ —     $ 8,406,932   Commercial and industrial     3,526,625       140,345       185,342       44,512       3,896,824   Fund banking     3,762,960       —       —       —       3,762,960   Securities-based loans     2,273,246       —       —       —       2,273,246   Construction and land     1,171,438       —       —       48,349       1,219,787   Commercial real estate     462,443       11,980       56,450       34,813       565,686   Home equity lines of credit     170,070       94       568       —       170,732   Other     53,338       76       —       —       53,414   Total   $ 19,821,820     $ 154,501     $ 245,586     $ 127,674     $ 20,349,581