Segment Information (Financial information by segment) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012 Locations	Jun. 30, 2011	Jun. 30, 2012 Locations	Jun. 30, 2011	Dec. 31, 2011
Segment Reporting Information [Line Items]
Number of geographic regions entity operates in (in locations)	12		12
Equipment rentals	$ 845	$ 524	$ 1,368	$ 958
Sales of rental equipment	81	41	157	73
Sales of new equipment	22	21	40	36
Contractor supplies sales	23	22	41	43
Service and other revenues	22	21	43	42
Total revenues	993	629	1,649	1,152
Depreciation and amortization expense	221	117	350	228
Equipment rentals gross profit	323	175	485	277
Capital expenditures			898	425
Assets	10,942		10,942		4,143
General Rentals [Member]
Segment Reporting Information [Line Items]
Equipment rentals	781	479	1,256	879
Sales of rental equipment	78	40	152	70
Sales of new equipment	20	18	37	32
Contractor supplies sales	21	20	37	40
Service and other revenues	21	20	41	40
Total revenues	921	577	1,523	1,061
Depreciation and amortization expense	209	109	328	214
Equipment rentals gross profit	293	156	437	244
Capital expenditures			853	391
Assets	10,485		10,485		3,776
Trench Safety, Power and HVAC [Member]
Segment Reporting Information [Line Items]
Equipment rentals	64	45	112	79
Sales of rental equipment	3	1	5	3
Sales of new equipment	2	3	3	4
Contractor supplies sales	2	2	4	3
Service and other revenues	1	1	2	2
Total revenues	72	52	126	91
Depreciation and amortization expense	12	8	22	14
Equipment rentals gross profit	30	19	48	33
Capital expenditures			45	34
Assets	$ 457		$ 457		$ 367