Allowance for Credit Losses - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended			9 Months Ended
	Mar. 31, 2023	Sep. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022	Dec. 31, 2021
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing receivable, collectively evaluated for impairment		$ 8,213,530			$ 8,213,530			$ 7,766,319
Financing receivable, allowance for credit losses, collectively evaluated for impairment		72,687			72,687			66,173
Financing receivable, individually evaluated for impairment and acquired with deteriorated credit quality		80,500			80,500
Financing receivable, allowance for credit losses, individually evaluated for impairment and acquired with deteriorated credit quality		2,500			2,500
Loans, individually evaluated for impairment		8,103			8,103			16,268
Allowance for credit losses, Individually evaluated for impairment		2,472			2,472			4,091
Charge-offs		217		$ 56	504	$ 8,229
Allowance for credit loss, available for sale		0		4,165	0	4,165	$ 0	310	$ 2,802	$ 83
Allowance for credit loss, held to maturity		146		152	146	152	$ 146	107	$ 190	$ 181
Debt securities, accrued interest after allowance for credit loss		8,300			8,300			8,700
Off-balance sheet, credit loss, liability		2,800			2,800			$ 3,000
Off-balance sheet, credit loss, liability, credit loss expense (reversal)		(65)		22	(229)	997
Charge-offs		0		0	(6,640)	0
(Benefit) provision for credit loss expense		0		1,363	6,330	4,082
Signature Bank
Financing Receivable, Allowance for Credit Loss [Line Items]
Charge-offs	$ (6,600)		$ (6,600)
(Benefit) provision for credit loss expense	$ 6,600		$ 6,600
Financial Asset, Other than Financial Asset Acquired with Credit Deterioration
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing receivable, allowance for credit losses, individually evaluated for impairment and acquired with deteriorated credit quality		2,500			2,500
Loans, individually evaluated for impairment		72,400			72,400
Charge-offs		$ 217		$ 56	$ 504	$ 595