Organization and Significant Accounting Policies - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) Rig JointVenture	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Apr. 30, 2015 Rig
Description Of Business And Basis Of Presentation [Line Items]
Number of drilling rigs | Rig	30
Number of jackups | Rig	14
Number of drillships | Rig	8
Number of semisubmersibles | Rig	8
Number of harsh environment jackup rigs under construction | Rig	1
Share exchanged for each ordinary shares	1
Number of joint ventures, where the company hold the variable interest | JointVenture	2
Percentage of variable interest in joint ventures	50.00%
Maturity period of highly liquid investments	Three months or less
Capital accruals	$ 44	$ 70
Period for incurring maintenance costs, Minimum	3 years
Period for incurring maintenance costs, Maximum	5 years
Deferred costs for major maintenance projects, net of accumulated depreciation	$ 202	179
Depreciation expense related to overhauls and asset replacement	75	77	$ 70
Deferred revenues under drilling contracts	180	263
Deferred expenses under drilling contracts	78	94
Loss reserves for personal injury and protection claims	21	$ 21
Aramco [Member]
Description Of Business And Basis Of Presentation [Line Items]
Number of rigs | Rig				5
Aramco [Member] | Prepaid Expenses and Other Current Assets [Member]
Description Of Business And Basis Of Presentation [Line Items]
Revenues recorded in excess of billings	$ 53
Minimum [Member] | Drilling Equipment [Member]
Description Of Business And Basis Of Presentation [Line Items]
Maximum useful life of property plant and equipment	3 years
Minimum [Member] | Other [Member]
Description Of Business And Basis Of Presentation [Line Items]
Maximum useful life of property plant and equipment	2 years
Maximum [Member] | Drilling Equipment [Member]
Description Of Business And Basis Of Presentation [Line Items]
Maximum useful life of property plant and equipment	30 years
Maximum [Member] | Other [Member]
Description Of Business And Basis Of Presentation [Line Items]
Maximum useful life of property plant and equipment	40 years