Statements of Condensed Consolidated Comprehensive (Loss) Income (Unaudited) (Parenthetical) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Other post-retirement benefits liability adjustments, tax			$ 10		$ 30
Other post-retirement benefits liability adjustments, tax		$ 23	$ 26	$ 71	$ 78
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201815Member			us-gaap:AccountingStandardsUpdate201802Member	us-gaap:AccountingStandardsUpdate201802Member