Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands		3 Months Ended				6 Months Ended
		Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Unrealized holding gains (losses) on available-for-sale securities during the period		$ (105,497)		$ 8,698		$ (217,894)	$ (6,236)
Reclassification adjustment for (gains) losses included in net income, pre-tax	[1]	31		(1)		31	(384)
Net unrealized holding (losses) gains		(105,466)		8,697		(217,863)	(6,620)
Change in funded status of post-retirement health plan, pre-tax		(2)				(3)
Net other comprehensive income (loss), pre-tax		(105,468)		8,697		(217,866)	(6,620)
Unrealized holding gains (losses) on available-for-sale securities during the period		22,154		(1,825)		45,758	1,311
Tax provision related to net realized gain	[1]	(6)		0		(7)	81
Net unrealized losses on available-for-sale securities		22,148		(1,825)		45,751	1,392
Change in funded status of post-retirement health plan, tax		0				0
Net other comprehensive income (loss), tax		22,148		(1,825)		45,751	1,392
Unrealized holding gains (losses) on available-for-sale securities during the period		(83,343)		6,873		(172,136)	(4,925)
Reclassification adjustment for (gains) losses included in net income, after-tax	[1]	25		(1)		24	(303)
Unrealized holding (losses) gains, net of reclassification and tax		(83,318)		6,872		(172,112)	(5,228)
Change in funded status of post-retirement plan, net of tax		(2)		0		(3)	0
Other comprehensive (loss) gain, net of tax		$ (83,320)	$ (88,795)	$ 6,872	$ (12,100)	$ (172,115)	$ (5,228)

[1] Pre-tax reclassification adjustments relating to available-for-sale securities are reported in security gains and the tax impact is included in income tax expense on the consolidated statements of income.