Accumulated Other Comprehensive Loss - Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Accumulated Other Comprehensive Income (Loss)
Beginning balance	$ 6,400,802	$ 5,084,066
Other comprehensive gain before reclassification	19,968
Amounts reclassified from other comprehensive income	387
Other comprehensive income, net	20,355	(38,166)
Ending balance	6,511,581	5,096,384
Total Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss)
Beginning balance	(164,002)	(17,932)
Ending balance	(143,647)	$ (56,098)
Unrealized Gains and Losses on Available for Sale (AFS) Securities
Accumulated Other Comprehensive Income (Loss)
Beginning balance	(127,818)
Other comprehensive gain before reclassification	17,170
Amounts reclassified from other comprehensive income	0
Other comprehensive income, net	17,170
Ending balance	(110,648)
Unrealized Gains and Losses on Derivatives
Accumulated Other Comprehensive Income (Loss)
Beginning balance	2,233
Other comprehensive gain before reclassification	2,798
Amounts reclassified from other comprehensive income	379
Other comprehensive income, net	3,177
Ending balance	5,410
Defined Benefit Pension and Postretirement Benefit Plans
Accumulated Other Comprehensive Income (Loss)
Beginning balance	(38,417)
Other comprehensive gain before reclassification	0
Amounts reclassified from other comprehensive income	8
Other comprehensive income, net	8
Ending balance	$ (38,409)