Fair Value of Financial Instruments (The Waha JVs) (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) pipeline	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Equity method investments, equity in earnings	$ 27,367	$ 23,855	$ 21,328
Unrealized gains (losses) on equity investee activity, net of tax	(15,023)	5,863	475
Equity Investee [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Equity method investments, net investment	$ 196,000	197,000
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 contributions	$ 1,000	28,000	73,000
Equity method investments, equity in earnings	27,300	23,900	21,300
Equity method investments, cumulative undistributed earnings	48,000
Equity method investments, distributions of earnings received, operating cash flows	9,100	10,900
Revenue, related parties			256,100
Unrealized gains (losses) on equity investee activity, before tax	(19,900)	7,700	800
Unrealized gains (losses) on equity investee activity, net of tax	(15,000)	5,900	$ 500
Waha JVs [Member] | Equity Investee [Member]
Fair Value, Financial Instruments Measured on a Non-Recurring Basis [Line Items]
Equity method investments, net investment	$ 174,000	$ 168,000