Drilling Fleet (Disposal) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Dispositions
Net cash proceeds from sale of assets			$ 7	$ 3
Gain (loss) on the sale of assets	$ 1	$ 1	(58)
Assets sold, not discontinued operations | Rig sales
Dispositions
Net cash proceeds from sale of assets			4	$ 2
Gain (loss) on the sale of assets			$ (60)
Gain (loss) on the sale of assets per diluted share			$ (0.10)
Gain (loss) on disposal of assets, tax effect			$ 0