Segment Information (Financial information by segment) (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Segment Reporting Information      
Equipment rentals $ 1,125 $ 1,005  
Sales of rental equipment 116 110  
Sales of new equipment 33 26  
Contractor supplies sales 18 19  
Service and other revenues 23 18  
Total revenues 1,315 1,178  
Gross profit 524 448  
Assets 12,282   12,467
Operating Segments      
Segment Reporting Information      
Equipment rentals 1,125 1,005  
Sales of rental equipment 116 110  
Sales of new equipment 33 26  
Contractor supplies sales 18 19  
Service and other revenues 23 18  
Total revenues 1,315 1,178  
Depreciation and amortization expense 304 277  
Capital expenditures 345 351  
Assets 12,282   12,467
Operating Segments | General rentals      
Segment Reporting Information      
Number of geographic regions entity operates in (locations) 12    
Equipment rentals 976 924  
Sales of rental equipment 108 106  
Sales of new equipment 26 24  
Contractor supplies sales 15 17  
Service and other revenues 19 17  
Total revenues 1,144 1,088  
Depreciation and amortization expense 262 259  
Capital expenditures 311 331  
Assets 10,788   10,935
Operating Segments | Trench, power and pump      
Segment Reporting Information      
Equipment rentals 149 81  
Sales of rental equipment 8 4  
Sales of new equipment 7 2  
Contractor supplies sales 3 2  
Service and other revenues 4 1  
Total revenues 171 90  
Depreciation and amortization expense 42 18  
Capital expenditures 34 20  
Assets 1,494   1,532
Equipment rentals      
Segment Reporting Information      
Gross profit 446 379  
Equipment rentals | Operating Segments      
Segment Reporting Information      
Gross profit 446 379  
Equipment rentals | Operating Segments | General rentals      
Segment Reporting Information      
Gross profit 383 344  
Equipment rentals | Operating Segments | Trench, power and pump      
Segment Reporting Information      
Gross profit $ 63 $ 35