Discontinued Operations (Details) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	May 31, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($) $ / shares	Nov. 30, 2012 item
Summarized results of discontinued operations
Income (loss) from discontinued operations, net of tax		$ 2	$ (20)
Proceeds from repayment of loans receivable		$ 15	101
Shelf Drilling Holdings, Ltd | Discontinued Operations, Disposed of by Sale
Summarized results of discontinued operations
Number of Drilling Units Sold | item				38
Operating revenues			166
Operating costs and related losses			160
Income (loss) from discontinued operations, net of tax			$ 8
Gain (loss) on the sale of assets, per diluted share | $ / shares			$ (0.02)
Income tax expense, discontinued operations			$ 14
ADTI | Discontinued Operations, Disposed of by Sale
Summarized results of discontinued operations
Proceeds from disposal of discontinued operations, net			10
Loss on disposal of assets in discontinued operations, net			$ (12)
Net loss on sale of assets per diluted share (in dollars per share) | $ / shares			$ (0.03)
(Gain) loss on disposal of assets in discontinued operations, tax effect			$ 0
Borrowings outstanding under working capital line of credit to buyer			$ 15
Proceeds from repayment of loans receivable	$ 15