Leased Facilities (Leased Facilities) (Details) $ in Millions	Dec. 31, 2015 USD ($)
Lease Payments Under Minimum Commitments, 2016	$ 1,653
Lease Payments Under Minimum Commitments, 2017	1,003
Lease Payments Under Minimum Commitments, 2018	555
Lease Payments Under Minimum Commitments, 2019	344
Lease Payments Under Minimum Commitments, 2020	265
Lease Payments Under Minimum Commitments, 2021 and beyond	1,057
Lease Payments Under Minimum Commitments, Total	4,877
Related Sublease Rental Income, 2016	7
Related Sublease Rental Income, 2017	6
Related Sublease Rental Income, 2018	2
Related Sublease Rental Income, 2019	2
Related Sublease Rental Income, 2020	2
Related Sublease Rental Income, 2021 and beyond	13
Related Sublease Rental Income, Total	32
Drilling Rigs and Related Equipment [Member]
Lease Payments Under Minimum Commitments, 2016	827
Lease Payments Under Minimum Commitments, 2017	408
Lease Payments Under Minimum Commitments, 2018	134
Lease Payments Under Minimum Commitments, 2019	89
Lease Payments Under Minimum Commitments, 2020	77
Lease Payments Under Minimum Commitments, 2021 and beyond	86
Lease Payments Under Minimum Commitments, Total	1,621
Other [Member]
Lease Payments Under Minimum Commitments, 2016	826
Lease Payments Under Minimum Commitments, 2017	595
Lease Payments Under Minimum Commitments, 2018	421
Lease Payments Under Minimum Commitments, 2019	255
Lease Payments Under Minimum Commitments, 2020	188
Lease Payments Under Minimum Commitments, 2021 and beyond	971
Lease Payments Under Minimum Commitments, Total	$ 3,256

Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 55
-Paragraph 40
-Subparagraph (Note 3)
-URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41502-112717

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41502-112717

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 55
-Paragraph 40
-Subparagraph (Note 3)
-URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Future minimum rental payments in aggregate as of the balance sheet date under operating leases.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6454179&loc=d3e41551-112718

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Future rental payments receivable within one year of the balance sheet date under an operating lease.

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Future rental payments receivable within the fifth year from the balance sheet date under an operating lease.

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Future rental payments receivable within the third year from the balance sheet date under an operating lease.

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Future minimum lease payments receivable under operating leases for periods greater than five years following the balance sheet date.

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