Accumulated Other Comprehensive (Loss) Income - Changes in components of AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accumulated Other Comprehensive (Loss) Income
Balance at the beginning of the period	$ (677,088)
Net comprehensive income (loss)	94,552	$ (655,942)	$ (68,735)
Balance at the end of the period	(582,536)	(677,088)
Benefit Plans
Accumulated Other Comprehensive (Loss) Income
Balance at the beginning of the period	(673)	57	(151)
Other comprehensive income (loss) before reclassifications	1,086	(838)	75
Amounts reclassified from accumulated other comprehensive loss	214	108	133
Net comprehensive income (loss)	1,300	(730)	208
Balance at the end of the period	627	(673)	57
Unrealized Gains and (Losses) on Securities Available for Sale
Accumulated Other Comprehensive (Loss) Income
Balance at the beginning of the period	(676,415)	(21,203)	47,740
Other comprehensive income (loss) before reclassifications	93,285	(655,189)	(68,865)
Amounts reclassified from accumulated other comprehensive loss	(33)	(23)	(78)
Net comprehensive income (loss)	93,252	(655,212)	(68,943)
Balance at the end of the period	(583,163)	(676,415)	(21,203)
Accumulated Other Comprehensive (Loss) Income
Accumulated Other Comprehensive (Loss) Income
Balance at the beginning of the period	(677,088)	(21,146)	47,589
Other comprehensive income (loss) before reclassifications	94,371	(656,027)	(68,790)
Amounts reclassified from accumulated other comprehensive loss	181	85	55
Net comprehensive income (loss)	94,552	(655,942)	(68,735)
Balance at the end of the period	$ (582,536)	$ (677,088)	$ (21,146)