Fair Value of Financial Instruments (The Waha JVs) (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Equity method investments, equity in earnings (losses)	$ 7,445	$ 6,966	$ 22,092	$ 19,778
Equity method investments, net investment	205,000		205,000		$ 196,000
Unrealized gains (losses) on equity investee activity, net of tax	2,839	(7,108)	(21,447)	(21,302)
Waha JVs [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Equity method investments, equity in earnings (losses)	7,700	6,900	22,900	19,800
Equity method investments, cumulative undistributed earnings	60,700		60,700
Equity method investments, distributions of earnings received, operating cash flows	2,400	1,500	10,200	7,500
Equity method investments, net investment	165,000		165,000		$ 174,000
Unrealized gains (losses) on equity investee activity, before tax	2,500	(9,400)	(29,500)	(28,200)
Unrealized gains (losses) on equity investee activity, net of tax	$ 1,900	$ (7,100)	$ (22,400)	$ (21,300)