Statements of Condensed Consolidated Equity (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Stockholders' Equity [Abstract]
Natural gas, tax		$ 10
Other post-retirement benefits liability adjustments, tax	$ 24	$ 26
Dividends declared per common share (in dollars per share)	$ 0.03	$ 0.03
Common stock, authorized shares (in shares)	320,000,000
Preferred stock authorized (in shares)	3,000,000
Preferred stock issued (in shares)	0
Preferred stock outstanding (in shares)	0