Shareholders' Equity (Roll Forward of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 1,275,250	$ 1,132,428	$ 1,201,749	$ 1,111,980
OCI, before reclassifications, net of tax	25,284	79,686	78,996	77,695
Amounts reclassified from AOCI, net of tax	431	1,243	2,554	1,686
Net OCI, current period	25,715	80,929	81,550	79,381
Ending balance	1,304,252	1,231,226	1,304,252	1,231,226
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(116,556)	(206,037)	(172,391)	(204,489)
Ending balance	(90,841)	(125,108)	(90,841)	(125,108)
Unrealized Investment Gains (Losses)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(116,675)	(211,070)	(176,053)	(206,327)
OCI, before reclassifications, net of tax	25,604	84,305	81,855	77,369
Amounts reclassified from AOCI, net of tax	966	2,311	4,093	4,504
Net OCI, current period	26,570	86,616	85,948	81,873
Ending balance	(90,105)	(124,454)	(90,105)	(124,454)
Cash Flow Hedging Gains (Losses)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	952	6,302	4,576	3,026
OCI, before reclassifications, net of tax	158	(4,619)	(2,381)	781
Amounts reclassified from AOCI, net of tax	(535)	(1,068)	(1,620)	(3,192)
Net OCI, current period	(377)	(5,687)	(4,001)	(2,411)
Ending balance	575	615	575	615
Non-credit Impairments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(11)	(92)	(92)	(11)
OCI, before reclassifications, net of tax	(478)	0	(478)	(455)
Amounts reclassified from AOCI, net of tax	0	0	81	374
Net OCI, current period	(478)	0	(397)	(81)
Ending balance	(489)	(92)	(489)	(92)
Unrecognized Change in Defined Benefit Plan Liabilities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(822)	(1,177)	(822)	(1,177)
OCI, before reclassifications, net of tax	0	0	0	0
Amounts reclassified from AOCI, net of tax	0	0	0	0
Net OCI, current period	0	0	0	0
Ending balance	$ (822)	$ (1,177)	$ (822)	$ (1,177)