Revenues and Accounts Receivable - Narrative (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Minimum Volume Commitments [Line Items]
Counterparty deficiencies billed	$ 302	$ 354
General payment terms	30 days
Substantially all trade accounts receivable, net, maximum age of balances past their scheduled invoice date	30 days	30 days
Minimum Volume Commitments
Minimum Volume Commitments [Line Items]
Counterparty deficiencies	$ 50	$ 42
Counterparty deficiencies billed	19	22
Counterparty deficiencies unbilled and uncollected	$ 31	$ 20