Income Taxes, Reconciliation (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Reconciliation of the benefit from (provision for) income taxes [Abstract]
Pre-Tax Net Book Income ("NBI")		$ 1,457	$ 1,177	$ 2,807	$ 2,550
Texas Margin Tax	[1]	(7)	(24)	(19)	(27)
State income tax provision, net of federal benefit		(1)	0	(1)	(1)
Federal income tax provision computed by applying the federal statutory rate to NBI of corporate entities		(4)	(4)	(7)	(7)
Valuation allowance	[2]	(3)	(3)	(7)	(6)
Other		(2)	0	(2)	0
Total provision for income taxes		$ (17)	$ (31)	$ (36)	$ (41)
Effective income tax rate		(1.20%)	(2.60%)	(1.30%)	(1.60%)

[1] Although the Texas Margin Tax is not considered a state income tax, it has the characteristics of an income tax since it is determined by applying a tax rate to a base that considers our Texas-sourced revenues and expenses.

[2] Management believes that it is more likely than not that the net deferred tax assets attributable to OTA will not be fully realizable.  Accordingly, we provided for a valuation allowance against OTA’s net deferred tax assets.