Fair Value of Financial Instruments (The Waha JVs) (Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Equity method investments, equity in earnings (losses)	$ 7,346,000	$ 7,834,000
Equity method investments, net investment	242,000,000		$ 220,000,000
Unrealized gains (losses) on equity investee activity, net of tax	13,839,000	(22,961,000)
Waha JVs [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Equity method investments, equity in earnings (losses)	7,700,000	7,600,000
Equity method investments, distributions of earnings received, operating cash flows	0	2,600,000
Equity method investments, cumulative undistributed earnings	75,000,000.0
Equity method investments, net investment	196,000,000		$ 175,000,000
Unrealized gains (losses) on equity investee activity, before tax	17,300,000	(30,300,000)
Unrealized gains (losses) on equity investee activity, net of tax	$ 13,100,000	$ (23,000,000.0)