Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 19,782	$ 14,495	$ 33,605	$ 7,484
Other comprehensive income, before tax:
Accumulated postretirement benefit obligation adjustment	0	0	0	(41)
Net unrealized gain (loss) on investments arising during the period	59	1,423	(691)	1,032
Reclassification adjustment for sale of securities included in net income	53	0	30	(30)
Reclassification adjustment for write-down of securities included in net income	0	0	0	482
Other comprehensive income (loss), before tax	112	1,423	(661)	1,443
Income tax benefit related to postretirement health benefits	0	0	0	(9)
Income tax expense (benefit) related to net unrealized gain (loss) on investments arising during the period	12	305	(146)	218
Income tax expense (benefit) related to reclassification adjustment for sale of securities included in net income	11	0	6	(6)
Income tax expense related to reclassification adjustment for write-down of securities included in net income	0	0	0	110
Net income tax expense (benefit) on other comprehensive income (loss)	23	305	(140)	313
Other comprehensive income (loss)	89	1,118	(521)	1,130
Comprehensive Income	$ 19,871	$ 15,613	$ 33,084	$ 8,614