Drilling Fleet (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Changes in construction work in progress, including capital expenditures and other capital additions, such as capitalized interest
Total capital expenditures	$ 100	$ 153
Construction in Progress
Changes in construction work in progress, including capital expenditures and other capital additions, such as capitalized interest
Construction work in progress, at beginning of period	828	753
Total capital expenditures	100	153
Changes in accrued capital additions	(9)	(31)
Property and equipment placed into service	(18)	(98)
Construction work in progress, at end of period	901	777
New builds
Changes in construction work in progress, including capital expenditures and other capital additions, such as capitalized interest
Total capital expenditures	77	70
Other equipment and construction projects
Changes in construction work in progress, including capital expenditures and other capital additions, such as capitalized interest
Total capital expenditures	$ 23	$ 83