Segment Information (Financial information by segment) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) location	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) location	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Segment Reporting Information
Equipment rentals	$ 1,326	$ 1,315	$ 3,671	$ 3,499
Sales of rental equipment	141	140	381	388
Sales of new equipment	38	42	110	105
Contractor supplies sales	21	23	60	64
Service and other revenues	24	24	72	65
Total revenues	1,550	1,544	4,294	4,121
Gross profit	690	688	1,832	1,725
Assets	12,598		12,598		$ 12,467
Operating Segments
Segment Reporting Information
Equipment rentals	1,326	1,315	3,671	3,499
Sales of rental equipment	141	140	381	388
Sales of new equipment	38	42	110	105
Contractor supplies sales	21	23	60	64
Service and other revenues	24	24	72	65
Total revenues	1,550	1,544	4,294	4,121
Depreciation and amortization expense	315	306	926	882
Capital expenditures			1,501	1,568
Assets	$ 12,598		$ 12,598		12,467
Operating Segments | General rentals
Segment Reporting Information
Number of geographic regions entity operates in (locations) | location	11		11
Equipment rentals	$ 1,120	1,127	$ 3,144	3,079
Sales of rental equipment	132	133	356	371
Sales of new equipment	33	31	94	80
Contractor supplies sales	18	19	51	55
Service and other revenues	23	21	65	55
Total revenues	1,326	1,331	3,710	3,640
Depreciation and amortization expense	272	267	798	789
Capital expenditures			1,325	1,391
Assets	11,019		11,019		10,935
Operating Segments | Trench, power and pump
Segment Reporting Information
Equipment rentals	206	188	527	420
Sales of rental equipment	9	7	25	17
Sales of new equipment	5	11	16	25
Contractor supplies sales	3	4	9	9
Service and other revenues	1	3	7	10
Total revenues	224	213	584	481
Depreciation and amortization expense	43	39	128	93
Capital expenditures			176	177
Assets	1,579		1,579		$ 1,532
Equipment rentals
Segment Reporting Information
Gross profit	607	599	1,588	1,481
Equipment rentals | Operating Segments
Segment Reporting Information
Gross profit	607	599	1,588	1,481
Equipment rentals | Operating Segments | General rentals
Segment Reporting Information
Gross profit	500	496	1,339	1,266
Equipment rentals | Operating Segments | Trench, power and pump
Segment Reporting Information
Gross profit	$ 107	$ 103	$ 249	$ 215