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Business Developments (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
	Feb. 02, 2026	Jun. 30, 2026	Mar. 31, 2026	Dec. 31, 2026	Jun. 30, 2026	Dec. 31, 2025	Dec. 31, 2024
Business Combination [Line Items]
Goodwill		$ 2,898,463			$ 2,898,463	$ 2,897,522	$ 2,868,068
Transaction Agreement, Webster Virginia Corporation And Webster Financial Corporation \| Banco Santander
Business Combination [Line Items]
Aggregate transaction value expected	$ 12,300,000
Transaction Agreement, Webster Financial Corporation
Business Combination [Line Items]
Merger-related expenses		$ 8,700			$ 17,900
Transaction Agreement, Webster Financial Corporation \| Banco Santander \| Forecast \| Subsequent Event
Business Combination [Line Items]
Price per share (in dollars per share)				$ 48.75
American depository receipts transferred (in shares)				2.0548
SecureSave
Business Combination [Line Items]
Measurement period adjustment			$ 900
SecureSave \| Healthcare Financial Services
Business Combination [Line Items]
Goodwill			$ 30,400