Goodwill and Other Intangible Assets - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Goodwill		$ 1,868,936,000	$ 1,868,936,000	$ 1,459,008,000
Goodwill impairment		0	0	0
Impairment of core deposits and intangibles		0	0	0
Net impairment (recovery of impairment) on loan servicing rights		0	0	865,000
Amortization expense - other intangible assets		39,800,000	37,800,000	21,800,000
Consumer Banking
Finite-Lived Intangible Assets [Line Items]
Goodwill		349,646,000	349,646,000	349,557,000
Goodwill from business combinations, as adjusted	$ 41,300,000
Commercial Lending
Finite-Lived Intangible Assets [Line Items]
Goodwill from business combinations, as adjusted	179,200,000
Investment Management
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 220,500,000
Residential mortgage
Finite-Lived Intangible Assets [Line Items]
Aggregate principal balances of mortgage loans serviced		$ 3,300,000,000	3,500,000,000	$ 3,600,000,000
Bank Leumi USA
Finite-Lived Intangible Assets [Line Items]
Goodwill from business combinations, as adjusted			400,600,000
Assets acquired and liabilities assumed other than goodwill			39,000,000
Landmark
Finite-Lived Intangible Assets [Line Items]
Goodwill from business combinations, as adjusted			4,400,000
Assets acquired and liabilities assumed other than goodwill			6,200,000
Westchester Bank Holding Corporation
Finite-Lived Intangible Assets [Line Items]
Goodwill from business combinations, as adjusted			$ 4,900,000
Core deposits
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period, years			10 years
Core deposits | Bank Leumi USA
Finite-Lived Intangible Assets [Line Items]
Intangible assets			$ 114,400,000
Other
Finite-Lived Intangible Assets [Line Items]
Weighted average amortization period, years			13 years 4 months 24 days