Commitments and Contingencies (Details 2) (USD $) In Millions, unless otherwise specified					3 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 South America Africa the Middle East and Asia Excluding Colombia	Dec. 31, 2012 Colombia	Dec. 31, 2010 Mexico	Dec. 31, 2012 Mexico	Dec. 31, 2012 Mexico Minimum	Dec. 31, 2012 Mexico Maximum
Income tax contingencies
Assessed income tax amount of NDIL's Mexico branch						$ 19.8
Aggregate potential tax assessments range							90	95
Income tax examination range of possible losses per year							6	26
Unrecognized tax benefits reductions resulting from lapse of applicable statute of limitations					7.4
Self-Insurance disclosures
Workers automobile claims	1.0
Employer's liability claims subject to per-occurrence deductible	2.0
General liability claims subject to per-occurrence deductible	5.0
Deductions in land rigs and for offshore rigs	5.0
Political risk insurance losses deductible			0.25
Political risk insurance deductible for foreign operation				0.5
Self-insurance accruals	171.2	157.8
Self-insurance recoveries/receivables	$ 24.6	$ 18.7