Bank Loans (Aging of the Recorded Investment in Past Due Loans) (Details) - USD ($)		Jun. 30, 2025		Dec. 31, 2024
Financing Receivable Recorded Investment Past Due [Line Items]
Total		$ 20,822,285,000		$ 20,879,745,000
Non-accrual		106,732,000	[1]	77,966,000	[2]
Nonperforming loans with no allowance		50,616,000	[1]	82,934,000	[2]
Total		157,348,000	[1]	160,900,000	[2]
Loans past due 90 days and still accruing interest		0		0
30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		36,505,000		72,100,000
90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		97,115,000		31,856,000
Financial Asset, Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		133,620,000		103,956,000
Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		20,688,665,000		20,775,789,000
Residential Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		8,906,739,000		8,565,193,000
Non-accrual		6,314,000	[1]	1,433,000	[2]
Nonperforming loans with no allowance		8,333,000	[1]	2,463,000	[2]
Total		14,647,000	[1]	3,896,000	[2]
Residential Real Estate [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		17,780,000		12,057,000
Residential Real Estate [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		14,647,000		4,273,000
Residential Real Estate [Member] | Financial Asset, Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		32,427,000		16,330,000
Residential Real Estate [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		8,874,312,000		8,548,863,000
Fund Banking [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		3,910,070,000		3,854,222,000
Fund Banking [Member] | Financial Asset, Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		0
Fund Banking [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		3,910,070,000		3,854,222,000
Commercial and Industrial [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		3,536,227,000		4,062,029,000
Non-accrual		99,955,000	[1]	76,254,000	[2]
Nonperforming loans with no allowance		742,000	[1]	13,504,000	[2]
Total		100,697,000	[1]	89,758,000	[2]
Commercial and Industrial [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		13,138,000		59,396,000
Commercial and Industrial [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		80,871,000		27,190,000
Commercial and Industrial [Member] | Financial Asset, Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		94,009,000		86,586,000
Commercial and Industrial [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		3,442,218,000		3,975,443,000
Securities-Based Loans [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		2,568,050,000		2,389,593,000
Securities-Based Loans [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		3,434,000
Securities-Based Loans [Member] | Financial Asset, Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		3,434,000
Securities-Based Loans [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		2,564,616,000		2,389,593,000
Commercial Real Estate [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		429,243,000		518,923,000
Nonperforming loans with no allowance	[2]			25,441,000
Total	[2]			25,441,000
Commercial Real Estate [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		429,243,000		518,923,000
Construction And Land [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		1,217,561,000		1,242,002,000
Nonperforming loans with no allowance		40,408,000	[1]	41,412,000	[2]
Total		40,408,000	[1]	41,412,000	[2]
Construction And Land [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		1,217,561,000		1,242,002,000
Home Equity Lines Of Credit [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		212,681,000		193,850,000
Non-accrual		409,000	[1]	201,000	[2]
Nonperforming loans with no allowance		1,107,000	[1]	114,000	[2]
Total		1,516,000	[1]	315,000	[2]
Home Equity Lines Of Credit [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		2,140,000		640,000
Home Equity Lines Of Credit [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		1,516,000		315,000
Home Equity Lines Of Credit [Member] | Financial Asset, Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		3,656,000		955,000
Home Equity Lines Of Credit [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		209,025,000		192,895,000
Other [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		41,714,000		53,933,000
Non-accrual		54,000	[1]	78,000	[2]
Nonperforming loans with no allowance	[1]	26,000
Total		80,000	[1]	78,000	[2]
Other [Member] | 30 - 89 Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		13,000		7,000
Other [Member] | 90 or More Days Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		81,000		78,000
Other [Member] | Financial Asset, Past Due [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		94,000		85,000
Other [Member] | Current Balance [Member]
Financing Receivable Recorded Investment Past Due [Line Items]
Total		$ 41,620,000		$ 53,848,000

[1] There were no loans past due 90 days and still accruing interest at June 30, 2025.

[2] There were no loans past due 90 days and still accruing interest at December 31, 2024.