Acquisition - Summary Of Merger Related Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Accounts Notes And Loans Receivable [Line Items]
Outside data processing software	$ 93,820	$ 74,492	$ 173,539	$ 140,243
Advertising and marketing	20,635	13,364	36,659	27,992
Peoples United Financial Inc [Member]
Accounts Notes And Loans Receivable [Line Items]
Salaries and employee benefits	85,299	4	85,386	4
Equipment and net occupancy	502		2,309
Outside data processing software	716	244	968	244
Advertising and marketing	1,199	24	1,827	24
Printing, postage and supplies	2,460	2,049	3,182	2,049
Other cost of operations	132,633	1,572	146,509	11,523
Other expenses	$ 222,809	$ 3,893	$ 240,181	$ 13,844