Acquisition and Divestitures - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands			9 Months Ended	12 Months Ended
	Oct. 30, 2022	Apr. 01, 2022	Dec. 31, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Oct. 31, 2022	Dec. 31, 2019
Business Acquisition [Line Items]
ACL for non-PCD loan and leases		$ 242,000
Initial estimate of expected credit losses		99,000
Goodwill			$ 8,490,089	$ 8,490,089	$ 4,593,112
Revenues				8,178,559	5,991,772	$ 5,954,761
Net income (loss)				1,991,663	1,858,746	1,353,152
Assets			200,729,841	200,729,841	155,107,160
Shareholders’ equity			25,317,990	25,317,990	17,903,405	16,187,283		$ 15,716,649
Trust Income [Member]
Business Acquisition [Line Items]
Revenue from contract with customer				740,717	644,716	601,884
Collective Investment Trust [Member] | Trust Income [Member]
Business Acquisition [Line Items]
Revenue from contract with customer				165,000	151,000	105,000
Common Stock [Member]
Business Acquisition [Line Items]
Shareholders’ equity			89,718	$ 89,718	79,871	79,871		$ 79,871
Minimum [Member]
Business Acquisition [Line Items]
Amortization period				3 years
Maximum [Member]
Business Acquisition [Line Items]
Amortization period				7 years
Peoples United Financial Inc [Member]
Business Acquisition [Line Items]
Business combination, market value		$ 8,400,000
Common stock, price per share		$ 164.66
ACL for non-PCD loan and leases		$ 242,000
Goodwill		3,908,245
Core deposit and other intangible assets		$ 261,000
Revenues			1,600,000
Net income (loss)			$ 165,000
Peoples United Financial Inc [Member] | Common Stock [Member]
Business Acquisition [Line Items]
Common stock issued in transaction		50,325,004
Peoples United Financial Inc [Member] | Core Deposit and Other Intangible Assets [Member] | Minimum [Member]
Business Acquisition [Line Items]
Amortization period		3 years
Peoples United Financial Inc [Member] | Core Deposit and Other Intangible Assets [Member] | Maximum [Member]
Business Acquisition [Line Items]
Amortization period		7 years
M T [Member]
Business Acquisition [Line Items]
Common stock, price per share		$ 0.118
M&T Insurance Agency, Inc [Member]
Business Acquisition [Line Items]
Revenues	$ 34,000				$ 37,000	$ 37,000
Gain (loss) on sale of subsidiary, pre-tax				$ 136,000
Gain (loss) on sale of subsidiary after-tax				$ 98,000
Assets							$ 18,000
Shareholders’ equity							$ 6,000