Statements of Condensed Consolidated Comprehensive (Loss) Income (Unaudited) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net (loss) income		$ (167,139)	$ 190,691
Other comprehensive income (loss), net of tax:
Net change in interest rate cash flow hedges, net of tax expense: $10 in 2019		0	42
Other post-retirement benefits liability adjustment, net of tax expense: $24 and $26		12	76
Change in accounting principle	[1]	0	(496)
Other comprehensive income (loss)		12	(378)
Comprehensive (loss) income		$ (167,127)	$ 190,313

[1] Related to adoption of Accounting Standards Update (ASU) 2018-02.