Revenue from Contracts with Customers - Narratives (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2018	Dec. 31, 2019
Disaggregation of Revenue
Amounts due from contracts with customers	$ 197.7		$ 384.0
Accounting Standards Update [Extensible List]		us-gaap:AccountingStandardsUpdate201802Member
Natural Gas, Oil, and NGLs Sales
Disaggregation of Revenue
Number of days in which payment is required	25 days