Significant Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based compensation expense
Share-based compensation expense	$ 42	$ 64	$ 98
Income tax benefit on share-based compensation expense	7	11	15
Capitalized interest
Capitalized interest costs on construction work in progress	176	140	133
Foreign currency
Net foreign currency exchange gain (loss)	(2)		$ 18
Cash and cash equivalents
Restricted cash investments	510	467
Restricted cash investments classified in other current assets	466	340
Restricted cash investments classified in other assets	44	127
Accounts receivable
Allowance for doubtful accounts	1	1
Materials and supplies
Materials and supplies, allowance for obsolescence	153	148
Assets held for sale
Assets held for sale, included in other current assets	$ 6	8
Property and equipment
Property and equipment as a percentage of total assets	78.00%
Maximum
Foreign currency
Net foreign currency exchange gain (loss)		$ 1
Drilling rig units | Minimum
Property and equipment
Estimated original useful life	20 years
Drilling rig units | Maximum
Property and equipment
Estimated original useful life	35 years
Buildings and improvements | Minimum
Property and equipment
Estimated original useful life	2 years
Buildings and improvements | Maximum
Property and equipment
Estimated original useful life	30 years
Machinery and equipment | Minimum
Property and equipment
Estimated original useful life	4 years
Machinery and equipment | Maximum
Property and equipment
Estimated original useful life	20 years