Use of Collateral (Details) - USD ($) $ in Millions		Jun. 30, 2020	Dec. 31, 2019
Financial Instruments Owned and Pledged as Collateral [Line Items]
Margin deposits	[1]	$ 290	$ 432
Natural gas and power prepayments		31	29
Total margin deposits and natural gas and power prepayments with our counterparties	[2]	321	461
Letters of credit issued		877	906
First priority liens under power and natural gas agreements		20	42
First priority liens under interest rate hedging instruments		168	31
Total letters of credit and first priority liens with our counterparties		1,065	979
Margin deposits held by us posted by our counterparties	[1],[3]	23	127
Letters of credit posted with us by our counterparties		212	25
Total margin deposits and letters of credit posted with us by our counterparties		235	152
Current and Non-current Derivative Assets and Liabilities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total margin deposits and natural gas and power prepayments with our counterparties	[2]	19	117
Margin deposits held by us posted by our counterparties		12	3
Other Current Liabilities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Margin deposits held by us posted by our counterparties		11	93
Prepaid Expenses and Other Current Assets
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total margin deposits and natural gas and power prepayments with our counterparties	[2]	294	336
Other Assets
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total margin deposits and natural gas and power prepayments with our counterparties	[2]	8	8
Other Noncurrent Liabilities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Margin deposits held by us posted by our counterparties		$ 0	$ 31

[1] We offset fair value amounts recognized for derivative instruments executed with the same counterparty under a master netting arrangement for financial statement presentation; therefore, amounts recognized for the right to reclaim, or the obligation to return, cash collateral are presented net with the corresponding derivative instrument fair values. See Note 6 for further discussion of our derivative instruments subject to master netting arrangements.

[2] At June 30, 2020 and December 31, 2019, $19 million and $117 million, respectively, were included in current and long-term derivative assets and liabilities, $294 million and $336 million, respectively, were included in margin deposits and other prepaid expense and $8 million and $8 million, respectively, were included in other assets on our Consolidated Condensed Balance Sheets.

[3] At June 30, 2020 and December 31, 2019, $12 million and $3 million, respectively, were included in current and long-term derivative assets and liabilities, $11 million and $93 million, respectively, were included in other current liabilities and nil and $31 million, respectively, were included in other long-term liabilities on our Consolidated Condensed Balance Sheets.