Drilling Fleet (Impairment held and used) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2017
Impairment of assets held and used
Loss associated with impairment, net of tax (per share)	$ 0.94
Midwater floaters
Impairment of assets held and used
Impairment of in use assets		$ 94
Loss associated with in use asset impairment, net of tax		$ 93
Loss associated with impairment, net of tax (per share)		$ 0.25

The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

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