Leases Summary of Lease Related Expenses (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017	[1]
Lessee, Lease, Description [Line Items]
Amortization of asset	$ 420
Interest on lease liabilities	202
Sublease income	1,419
Net lease expense	400,764
Variable lease expenses primarily related to additional volumes processed at gas processing plant		$ 28,700
Lease operating expenses		605,180	$ 353,832	[1]	$ 299,420
Selling and general expenses		232,736	205,192	[1]	$ 207,391
Property, plant and equipment, Net		9,969,743	8,432,133	[2]
Asset Retirement Obligation, Current		39,315	$ 47,598
Property, plant and equipment
Lessee, Lease, Description [Line Items]
Operating lease cost	133,837
Property, plant and equipment, Net		102,700
Asset retirement obligations
Lessee, Lease, Description [Line Items]
Operating lease cost	3,024
Asset Retirement Obligation, Current		3,000
Lease operating expenses
Lessee, Lease, Description [Line Items]
Operating lease cost	249,787
Lease operating expenses		56,300
Selling and general expense
Lessee, Lease, Description [Line Items]
Operating lease cost	12,325
Selling and general expenses		4,300
Other operating expense
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 2,588
Other expense (benefit)		$ 2,600

[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)