Business Combinations (Details) In Millions, except Share data in Billions, unless otherwise specified	3 Months Ended
	Jun. 30, 2012 ERA Mining Machinery Limited USD ($) types	Oct. 31, 2012 ERA Mining Machinery Limited USD ($)	Sep. 30, 2012 ERA Mining Machinery Limited USD ($)	May 31, 2012 ERA Mining Machinery Limited	Jun. 30, 2012 ERA Mining Machinery Limited Cash Consideration HKD	Jun. 30, 2012 ERA Mining Machinery Limited Loan note consideration HKD	Sep. 30, 2012 Caterpillar Tohoku Limited USD ($)	Jul. 31, 2012 Caterpillar Tohoku Limited USD ($)	Mar. 31, 2012 Caterpillar Tohoku Limited USD ($)
Business Acquisition
Percentage of equity acquired (as a percent)		1.00%		99.00%					100.00%
Percentage of issued shares outstanding and unacquired (as a percent)			1.00%
Purchase price of acquired entity	$ 690								$ 206
Cost of acquisition, net cash paid	453
Cost of acquisition paid in cash	475	7						22	59
Cash acquired	22								18
Far value of loan notes issued for shares	169
Third party liabilities assumed	155								77
Loan and interest payable to Caterpillar	51
Restricted cash acquired	138
Fair value of noncontrolling interest	7
Loan notes debt component, minimum redemption amount	152
Loan notes, fair value of contingent consideration	17
Trade payables acquired due to Caterpillar									64
Estimated consideration payable							3
Business Combination, Alternate considerations to acquiree
Number of consideration alternatives	2
Value of Consideration to be paid (in HKD/share)					0.88	1.00
Contingent consideration arrangement, value minimum (in HKD/share)						0.75
Contingent consideration arrangement, value maximum (HKD/share)						1.15
Number of shares tendered (in shares)					4.0	1.6
Assets Acquired
Tangible assets acquired	659								252
Cash	22								18
Restricted cash	138
Receivables	213								34
Inventory	94								26
Property, plant and equipment	112								157
Finite-lived intangible assets	194								8
Goodwill	476		476				19		19
Finite-lived intangible assets, weighted average useful life (in years)	15 years
Liabilities Acquired
Total liabilities assumed	592								132
Accounts payable	342								39
Third party liabilities	155								77
Accrued expenses	50
Deferred tax liabilities	$ 36