Fair Value of Financial Instruments (The Waha JVs) (Narrative) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) pipeline	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) pipeline	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Equity method investments, equity in earnings (losses)	$ 6,813	$ 6,551	$ 14,647	$ 12,811
Equity method investments, net investment	197,000		197,000		$ 196,000
Unrealized gains (losses) on equity investee activity, net of tax	$ (1,325)	(8,732)	$ (24,286)	(14,194)
Waha JVs [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Number of pipelines in operation | pipeline	2		2
Equity method investments, equity in earnings (losses)	$ 7,600	6,600	$ 15,300	12,900
Equity method investments, cumulative undistributed earnings	55,400		55,400
Equity method investments, distributions of earnings received, operating cash flows	5,200	2,100	7,900	6,000
Equity method investments, net investment	157,000		157,000		$ 174,000
Unrealized gains (losses) on equity investee activity, before tax	(1,700)	(11,600)	(32,000)	(18,800)
Unrealized gains (losses) on equity investee activity, net of tax	$ (1,300)	$ (8,700)	$ (24,300)	$ (14,200)