Segment Information (Financial information by segment) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013 Locations	Sep. 30, 2012	Sep. 30, 2013 Locations	Sep. 30, 2012	Dec. 31, 2012
Segment Reporting, Measurement Disclosures [Abstract]
Number of geographic regions entity operates in (in locations)	12		12
Segment Reporting Information [Line Items]
Equipment rentals	$ 1,138	$ 1,051	$ 3,063	$ 2,419
Sales of rental equipment	102	101	356	258
Sales of new equipment	29	24	74	64
Contractor supplies sales	23	23	66	64
Service and other revenues	19	20	58	63
Total revenues	1,311	1,219	3,617	2,868
Depreciation and amortization expense			814	625
Equipment rentals gross profit	497	452	1,220	937
Assets	11,563		11,563		11,026
Operating Segments [Member]
Segment Reporting Information [Line Items]
Equipment rentals	1,138	1,051	3,063	2,419
Sales of rental equipment	102	101	356	258
Sales of new equipment	29	24	74	64
Contractor supplies sales	23	23	66	64
Service and other revenues	19	20	58	63
Total revenues	1,311	1,219	3,617	2,868
Depreciation and amortization expense	278	275	814	625
Equipment rentals gross profit	497	452	1,220	937
Capital expenditures			1,570	1,185
Assets	11,563		11,563		11,026
Operating Segments [Member] | General rentals [Member]
Segment Reporting Information [Line Items]
Equipment rentals	1,038	971	2,824	2,227
Sales of rental equipment	98	98	343	250
Sales of new equipment	27	22	69	59
Contractor supplies sales	21	21	60	58
Service and other revenues	18	19	54	60
Total revenues	1,202	1,131	3,350	2,654
Depreciation and amortization expense	261	264	771	592
Equipment rentals gross profit	445	410	1,106	847
Capital expenditures			1,461	1,112
Assets	11,004		11,004		10,545
Operating Segments [Member] | Trench safety, power and HVAC [Member]
Segment Reporting Information [Line Items]
Equipment rentals	100	80	239	192
Sales of rental equipment	4	3	13	8
Sales of new equipment	2	2	5	5
Contractor supplies sales	2	2	6	6
Service and other revenues	1	1	4	3
Total revenues	109	88	267	214
Depreciation and amortization expense	17	11	43	33
Equipment rentals gross profit	52	42	114	90
Capital expenditures			109	73
Assets	$ 559		$ 559		$ 481