Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Accumulated other comprehensive income (loss), net of tax
AOCI (loss), beginning of period	$ (7,414)
Change in unrealized holding gains (losses) on available-for-sale securities	10,494	$ (26,919)
Pension and other postretirement plans, OCI	(2,742)	1,730
OCI (loss)	7,752	(25,189)
AOCI (loss), end of period	338
Investment securities:
Accumulated other comprehensive income (loss), before tax
AOCI (loss), beginning of period	(66,571)	7,722
OCI (loss) before reclassifications	10,032	(36,371)
Realized investment losses	1,619	2,080
Impairment losses	1,633	216
Investment securities, OCI (loss)	13,284	(34,075)
AOCI (loss), end of period	(53,287)	(26,353)
Accumulated other comprehensive income (loss), tax
AOCI (loss), beginning of period	(13,980)	1,621
OCI (loss) before reclassifications	2,107	(7,638)
Realized investment losses	340	437
Impairment losses	343	45
Investment securities, OCI (loss)	2,790	(7,156)
AOCI (loss), end of period	(11,190)	(5,535)
Accumulated other comprehensive income (loss), net of tax
AOCI (loss), beginning of period	(52,591)	6,101
OCI (loss) before reclassifications	7,925	(28,733)
Realized investment losses	1,279	1,643
Impairment losses	1,290	171
Change in unrealized holding gains (losses) on available-for-sale securities	10,494	(26,919)
AOCI (loss), end of period	(42,097)	(20,818)
Pension and other postretirement plans:
Accumulated other comprehensive income (loss), before tax
AOCI (loss), beginning of period	57,186	(39,734)
Amortization of prior service costs	362	361
Amortization of net actuarial (gain) loss	(3,833)	1,830
Pension and other postretirement plans, OCI	(3,471)	2,191
AOCI (loss), end of period	53,715	(37,543)
Accumulated other comprehensive income (loss), tax
AOCI (loss), beginning of period	12,009	(8,345)
Amortization of prior service costs	76	76
Amortization of net actuarial (gain) loss	(805)	385
Pension and other postretirement plans, OCI	(729)	461
AOCI (loss), end of period	11,280	(7,884)
Accumulated other comprehensive income (loss), net of tax
AOCI (loss), beginning of period	45,177	(31,389)
Amortization of prior service costs	286	285
Amortization of net actuarial (gain) loss	(3,028)	1,445
Pension and other postretirement plans, OCI	(2,742)	1,730
AOCI (loss), end of period	42,435	(29,659)
Total
Accumulated other comprehensive income (loss), before tax
AOCI (loss), beginning of period	(9,385)	(32,012)
Investment securities, OCI (loss)	13,284	(34,075)
Pension and other postretirement plans, OCI	(3,471)	2,191
OCI (loss)	9,813	(31,884)
AOCI (loss), end of period	428	(63,896)
Accumulated other comprehensive income (loss), tax
AOCI (loss), beginning of period	(1,971)	(6,724)
Investment securities, OCI (loss)	2,790	(7,156)
Pension and other postretirement plans, OCI	(729)	461
OCI (loss)	2,061	(6,695)
AOCI (loss), end of period	90	(13,419)
Accumulated other comprehensive income (loss), net of tax
AOCI (loss), beginning of period	(7,414)	(25,288)
Change in unrealized holding gains (losses) on available-for-sale securities	10,494	(26,919)
Pension and other postretirement plans, OCI	(2,742)	1,730
OCI (loss)	7,752	(25,189)
AOCI (loss), end of period	$ 338	$ (50,477)