Fair Value of Financial Instruments (The Waha JVs) (Narrative) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) pipeline	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Equity method investments, equity in earnings (losses)	$ 7,834	$ 6,260
Equity method investments, net investment	195,000		$ 196,000
Unrealized gains (losses) on equity investee activity, net of tax	$ (22,961)	(5,462)
Waha JVs [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Number of pipelines in operation | pipeline	2
Equity method investments, equity in earnings (losses)	$ 7,600	6,300
Equity method investments, cumulative undistributed earnings	53,100
Equity method investments, distributions of earnings received, operating cash flows	2,600	3,900
Equity method investments, net investment	156,000		$ 174,000
Unrealized gains (losses) on equity investee activity, before tax	(30,300)	(7,200)
Unrealized gains (losses) on equity investee activity, net of tax	$ (23,000)	$ (5,500)