Fair Value of Financial Instruments (The Waha JVs) (Narrative) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Equity method investments, equity in earnings (losses)	$ 7,525,000	$ 6,813,000	$ 14,871,000	$ 14,647,000
Equity method investments, net investment	248,000,000		248,000,000		$ 220,000,000
Unrealized gains (losses) on equity investee activity, net of tax	(3,465,000)	(1,325,000)	10,374,000	(24,286,000)
Waha JVs
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Equity method investments, equity in earnings (losses)	8,600,000	7,600,000	16,300,000	15,300,000
Equity method investments, distributions of earnings received, operating cash flows	0	5,200,000	0	7,900,000
Equity method investments, cumulative undistributed earnings	83,600,000		83,600,000
Equity method investments, net investment	201,000,000		201,000,000		$ 175,000,000
Unrealized gains (losses) on equity investee activity, before tax	(4,900,000)	(1,700,000)	12,300,000	(32,000,000.0)
Unrealized gains (losses) on equity investee activity, net of tax	$ (3,700,000)	$ (1,300,000)	$ 9,400,000	$ (24,300,000)