Bank Loans (Schedule of Balance and Associated Percentage of Each Major Loan Category in Bank Loan Portfolio) (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total risk category of loan portfolio	$ 20,879,745	$ 19,441,467
Loans in process/(unapplied loan payments), net	(2,885)	1,108
Unamortized loan fees, net	(5,756)	(8,478)
Allowance for loan losses	(139,308)	(128,292)	$ (111,653)
Loans held for investment, net	$ 20,731,796	$ 19,305,805
Gross bank loans, Percent	100.00%	100.00%
Residential Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total risk category of loan portfolio	$ 8,565,193	$ 8,047,647
Allowance for loan losses	$ (11,061)	$ (13,855)	(20,441)
Gross bank loans, Percent	41.00%	41.40%
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total risk category of loan portfolio	$ 4,062,029	$ 3,566,987
Allowance for loan losses	$ (92,698)	$ (67,077)	(54,143)
Gross bank loans, Percent	19.50%	18.30%
Fund Banking [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total risk category of loan portfolio	$ 3,854,222	$ 3,633,126
Allowance for loan losses	$ (10,792)	$ (10,173)	(11,711)
Gross bank loans, Percent	18.50%	18.70%
Securities-Based Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total risk category of loan portfolio	$ 2,389,593	$ 2,306,455
Allowance for loan losses	$ (2,917)	$ (3,035)	(3,157)
Gross bank loans, Percent	11.40%	11.90%
Construction And Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total risk category of loan portfolio	$ 1,242,002	$ 1,034,370
Allowance for loan losses	$ (12,866)	$ (11,817)	(8,568)
Gross bank loans, Percent	5.90%	5.30%
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total risk category of loan portfolio	$ 518,923	$ 660,631
Allowance for loan losses	$ (8,057)	$ (21,386)	(12,897)
Gross bank loans, Percent	2.50%	3.40%
Home Equity Lines Of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total risk category of loan portfolio	$ 193,850	$ 136,270
Allowance for loan losses	$ (317)	$ (371)	(364)
Gross bank loans, Percent	0.90%	0.70%
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total risk category of loan portfolio	$ 53,933	$ 55,981
Allowance for loan losses	$ (600)	$ (578)	$ (372)
Gross bank loans, Percent	0.30%	0.30%