Restructuring Charges (Restructuring Liability) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges	$ 59	$ 96	$ 232	$ 331	$ 0
North America [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				76
Middle East/North Africa/Asia [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				133
Europe/Sub-Sahara Africa/Russia [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				35
Latin America [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				48
Corporate and Research and Development [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				30
Drilling Rigs [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				9
Severance and Other Restructuring Liabilities [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				331
Restructuring and Related Cost, Incurred Cost			168
Restructuring Reserve [Roll Forward]
Accrued balance at beginning of period	79		79
Cash Payments			(193)	(106)
Other			3
Accrued balance at end of period			51	79
Severance and Other Restructuring Liabilities [Member] | Operating Segments [Member] | North America [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			8
Severance and Other Restructuring Liabilities [Member] | Operating Segments [Member] | Middle East/North Africa/Asia [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			11
Severance and Other Restructuring Liabilities [Member] | Operating Segments [Member] | Europe/Sub-Sahara Africa/Russia [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			18
Severance and Other Restructuring Liabilities [Member] | Operating Segments [Member] | Latin America [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			1
Severance and Other Restructuring Liabilities [Member] | Corporate and Research and Development [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			13
Severance and Other Restructuring Liabilities [Member] | Core Regional Segments [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			38
Severance and Other Restructuring Liabilities [Member] | Drilling Rigs [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			0
2015 Plan [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				58
Restructuring and Related Cost, Incurred Cost			149
Restructuring Reserve [Roll Forward]
Accrued balance at beginning of period	53		53
Cash Payments			(168)
Other			2
Accrued balance at end of period			32	53
2015 Plan [Member] | Employee Severance [Member] | North America [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			7
2015 Plan [Member] | Employee Severance [Member] | Middle East/North Africa/Asia [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			7
2015 Plan [Member] | Employee Severance [Member] | Europe/Sub-Sahara Africa/Russia [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			9
2015 Plan [Member] | Employee Severance [Member] | Latin America [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			1
2015 Plan [Member] | Employee Severance [Member] | Corporate and Research and Development [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			8
2015 Plan [Member] | Employee Severance [Member] | Core Regional Segments [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			24
2015 Plan [Member] | Employee Severance [Member] | Drilling Rigs [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			0
2015 Plan [Member] | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges			19
Restructuring Reserve [Roll Forward]
Accrued balance at beginning of period	0		0
Cash Payments			(12)
Other			(1)
Accrued balance at end of period			8	0
2015 Plan [Member] | Other Restructuring [Member] | North America [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			0
2015 Plan [Member] | Other Restructuring [Member] | Middle East/North Africa/Asia [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			0
2015 Plan [Member] | Other Restructuring [Member] | Europe/Sub-Sahara Africa/Russia [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			8
2015 Plan [Member] | Other Restructuring [Member] | Latin America [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			0
2015 Plan [Member] | Other Restructuring [Member] | Corporate and Research and Development [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			0
2015 Plan [Member] | Other Restructuring [Member] | Core Regional Segments [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			8
2015 Plan [Member] | Other Restructuring [Member] | Drilling Rigs [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			0
2015 Plan [Member] | Severance and Other Restructuring Liabilities [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges			232	58
2015 Plan [Member] | Severance and Other Restructuring Liabilities [Member] | Operating Segments [Member] | North America [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges			52	32
2015 Plan [Member] | Severance and Other Restructuring Liabilities [Member] | Operating Segments [Member] | Middle East/North Africa/Asia [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges			56	8
2015 Plan [Member] | Severance and Other Restructuring Liabilities [Member] | Operating Segments [Member] | Europe/Sub-Sahara Africa/Russia [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges			56	5
2015 Plan [Member] | Severance and Other Restructuring Liabilities [Member] | Operating Segments [Member] | Latin America [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges			40	12
2015 Plan [Member] | Severance and Other Restructuring Liabilities [Member] | Corporate and Research and Development [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges			16	1
2015 Plan [Member] | Severance and Other Restructuring Liabilities [Member] | Core Regional Segments [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges			204	57
2015 Plan [Member] | Severance and Other Restructuring Liabilities [Member] | Drilling Rigs [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges			12	0
2014 Plan [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost			0
Restructuring Reserve [Roll Forward]
Accrued balance at beginning of period	14		14
Cash Payments			(7)
Other			2
Accrued balance at end of period			5	14
2014 Plan [Member] | Employee Severance [Member] | North America [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			0
2014 Plan [Member] | Employee Severance [Member] | Middle East/North Africa/Asia [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			0
2014 Plan [Member] | Employee Severance [Member] | Europe/Sub-Sahara Africa/Russia [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			0
2014 Plan [Member] | Employee Severance [Member] | Latin America [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			0
2014 Plan [Member] | Employee Severance [Member] | Corporate and Research and Development [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			5
2014 Plan [Member] | Employee Severance [Member] | Core Regional Segments [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			0
2014 Plan [Member] | Employee Severance [Member] | Drilling Rigs [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			0
2014 Plan [Member] | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				24
Restructuring and Related Cost, Incurred Cost			0
Restructuring Reserve [Roll Forward]
Accrued balance at beginning of period	$ 12		12
Cash Payments			(6)
Other			0
Accrued balance at end of period			6	12
2014 Plan [Member] | Other Restructuring [Member] | North America [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			1
2014 Plan [Member] | Other Restructuring [Member] | Middle East/North Africa/Asia [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			4
2014 Plan [Member] | Other Restructuring [Member] | Europe/Sub-Sahara Africa/Russia [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			1
2014 Plan [Member] | Other Restructuring [Member] | Latin America [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			0
2014 Plan [Member] | Other Restructuring [Member] | Corporate and Research and Development [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			0
2014 Plan [Member] | Other Restructuring [Member] | Core Regional Segments [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			6
2014 Plan [Member] | Other Restructuring [Member] | Drilling Rigs [Member]
Restructuring Reserve [Roll Forward]
Accrued balance at end of period			$ 0
2014 Plan [Member] | Severance and Other Restructuring Liabilities [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				273
2014 Plan [Member] | Severance and Other Restructuring Liabilities [Member] | Operating Segments [Member] | North America [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				44
2014 Plan [Member] | Severance and Other Restructuring Liabilities [Member] | Operating Segments [Member] | Middle East/North Africa/Asia [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				125
2014 Plan [Member] | Severance and Other Restructuring Liabilities [Member] | Operating Segments [Member] | Europe/Sub-Sahara Africa/Russia [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				30
2014 Plan [Member] | Severance and Other Restructuring Liabilities [Member] | Operating Segments [Member] | Latin America [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				36
2014 Plan [Member] | Severance and Other Restructuring Liabilities [Member] | Corporate and Research and Development [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				29
2014 Plan [Member] | Severance and Other Restructuring Liabilities [Member] | Core Regional Segments [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				235
2014 Plan [Member] | Severance and Other Restructuring Liabilities [Member] | Drilling Rigs [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				$ 9