Bank Loans (Schedule of Balance and Associated Percentage of Each Major Loan Category in Bank Loan Portfolio) (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total risk category of loan portfolio	$ 20,822,285		$ 20,879,745
Loans in process/(unapplied loan payments), net	(11,437)		(2,885)
Unamortized loan fees, net	(28,020)		(5,756)
Allowance for credit losses on loans	(135,734)	$ (140,061)	(139,308)	$ (135,114)	$ (130,213)	$ (128,292)
Loans held for investment, net	$ 20,647,094		$ 20,731,796
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	$ 8,906,739		$ 8,565,193
Allowance for credit losses on loans	$ (13,767)	(11,172)	$ (11,061)	(11,242)	(12,507)	(13,855)
Gross bank loans, Percent	42.80%		41.00%
Fund Banking [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total risk category of loan portfolio	$ 3,910,070		$ 3,854,222
Allowance for credit losses on loans	$ (10,948)	(10,246)	$ (10,792)	(12,179)	(8,763)	(10,173)
Gross bank loans, Percent	18.80%		18.50%
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total risk category of loan portfolio	$ 3,536,227		$ 4,062,029
Allowance for credit losses on loans	$ (84,981)	(92,294)	$ (92,698)	(76,354)	(65,887)	(67,077)
Gross bank loans, Percent	17.00%		19.50%
Securities-Based Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total risk category of loan portfolio	$ 2,568,050		$ 2,389,593
Allowance for credit losses on loans	$ (3,128)	(2,928)	$ (2,917)	(2,813)	(3,068)	(3,035)
Gross bank loans, Percent	12.30%		11.40%
Construction And Land [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total risk category of loan portfolio	$ 1,217,561		$ 1,242,002
Allowance for credit losses on loans	$ (12,854)	(13,251)	$ (12,866)	(16,379)	(18,589)	(11,817)
Gross bank loans, Percent	5.80%		5.90%
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total risk category of loan portfolio	$ 429,243		$ 518,923
Allowance for credit losses on loans	$ (8,795)	(9,366)	$ (8,057)	(15,312)	(20,689)	(21,386)
Gross bank loans, Percent	2.10%		2.50%
Home Equity Lines Of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total risk category of loan portfolio	$ 212,681		$ 193,850
Allowance for credit losses on loans	$ (660)	(170)	$ (317)	(362)	(246)	(371)
Gross bank loans, Percent	1.00%		0.90%
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total risk category of loan portfolio	$ 41,714		$ 53,933
Allowance for credit losses on loans	$ (601)	$ (634)	$ (600)	$ (473)	$ (464)	$ (578)
Gross bank loans, Percent	0.20%		0.30%