Assets and Liabilities Measured at Fair Value - Narratives (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) OffsettingPosition	Dec. 31, 2018 USD ($)	[1],[2]	Dec. 31, 2017 USD ($)	[1],[2]
Expected life	3 years
Number of offsetting positions | OffsettingPosition	0
Impairment of assets | $	$ 0	$ 20,000,000		$ 0
Contingent consideration
Expected life	6 years
Fair value, expected volatility rate	30.00%
Risk-free interest rate	1.66%

[1] ¹ Reclassified to conform with current presentation (see Notes C and E). 2017 revenue is presented net of $58.9 million of transportation, gathering and processing costs as historically shown prior to the adoption of ASC 606 on January 1, 2018. See Notes to Consolidated Financial Statements, page 58.

[2] Reclassified to conform with current presentation (see Note E)