Consolidated Statements Of Cash Flows (Parenthetical) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Statement of Cash Flows [Abstract]
Deferred tax provision related to unrealized gain (loss) on investments	$ (333)	$ (601)
Adjustments to postretirement benefits obligation, net of deferred tax benefit provision	$ 9	$ 0