Postemployment Benefit Plans (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net periodic benefit costs, before tax
Service cost	$ 65	$ 63
Interest cost	83	77
Special termination benefits		3
Net periodic benefit costs	88	91	87
Unrecognized accumulated other comprehensive income, before tax
Actuarial loss, net	564	378
Prior service (credit), net	(12)	(8)
Transition obligation, net	(2)	1
Total	550	371
Accumulated other comprehensive income expected to be recognized during the next fiscal year
Actuarial loss, net	43
Prior service cost (credit), net	(2)
Total amount expected to be recognized	41
Pension and Other Postretirement Benefit Contributions [Abstract]
Defined benefit plan contributions funded by cash flows from operations	103	118	73
Projected pension benefits payments
2012	54
2013	57
2014	60
2015	63
2016	67
2017-2021	401
Transocean Plans
Net periodic benefit costs, before tax
Service cost	64	62	62
Interest cost	80	74	67
Expected return on plan assets	(86)	(75)	(71)
Settlements and curtailments	3	8	6
Special termination benefits		(3)
Actuarial losses, net	27	17	20
Prior service cost (credit), net	(1)	(1)
Transition obligation, net		1
Net periodic benefit costs	87	89	84
Pension and Other Postretirement Benefit Contributions [Abstract]
Expected defined plan contributions in 2012	145
U.S. Plans
Net periodic benefit costs, before tax
Service cost	43	42	44
Interest cost	58	54	50
Expected return on plan assets	(63)	(58)	(55)
Settlements and curtailments	2	5	4
Special termination benefits		(3)
Actuarial losses, net	23	13	18
Prior service cost (credit), net	(1)	(1)	(1)
Net periodic benefit costs	62	58	60
Unrecognized accumulated other comprehensive income, before tax
Actuarial loss, net	447	319
Prior service (credit), net	(10)	(11)
Total	437	308
Accumulated other comprehensive income expected to be recognized during the next fiscal year
Actuarial loss, net	39
Prior service cost (credit), net	(1)
Total amount expected to be recognized	38
Projected pension benefits payments
2012	41
2013	44
2014	47
2015	50
2016	54
2017-2021	319
Non-U.S. Plans
Net periodic benefit costs, before tax
Service cost	21	20	18
Interest cost	22	20	17
Expected return on plan assets	(23)	(17)	(16)
Settlements and curtailments	1	3	2
Actuarial losses, net	4	4	2
Prior service cost (credit), net			1
Transition obligation, net		1
Net periodic benefit costs	25	31	24
Unrecognized accumulated other comprehensive income, before tax
Actuarial loss, net	113	52
Prior service (credit), net		8
Transition obligation, net	(2)	1
Total	111	61
Accumulated other comprehensive income expected to be recognized during the next fiscal year
Actuarial loss, net	4
Total amount expected to be recognized	4
Projected pension benefits payments
2012	10
2013	10
2014	10
2015	9
2016	9
2017-2021	62
OPEB Plans
Net periodic benefit costs, before tax
Service cost	1	1
Interest cost	3	3
Net periodic benefit costs	1	2	3
Unrecognized accumulated other comprehensive income, before tax
Actuarial loss, net	4	7
Prior service (credit), net	(2)	(5)
Total	2	2
Accumulated other comprehensive income expected to be recognized during the next fiscal year
Prior service cost (credit), net	(1)
Total amount expected to be recognized	(1)
Pension and Other Postretirement Benefit Contributions [Abstract]
Expected defined plan contributions in 2012	3
Projected pension benefits payments
2012	3
2013	3
2014	3
2015	4
2016	4
2017-2021	$ 20