Drilling Fleet (Disposal) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) item	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) item	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Dispositions
Number of mobile offshore drilling units | item	38		38
Net cash proceeds from sale of assets			$ 15	$ 52
Gain (loss) on the sale of assets	$ (64)	$ (4)	(64)	(7)
Assets held for sale, included in other current assets	$ 9		9		$ 0
Assets sold, not discontinued operations | Rig sales
Dispositions
Net cash proceeds from sale of assets			11	47
Gain (loss) on the sale of assets			(61)	2
Gain (loss) on disposal of assets, tax effect			$ 0	0
Assets sold, not discontinued operations | Other property and equipment
Dispositions
Net cash proceeds from sale of assets				5
Gain (loss) on the sale of assets				$ (9)