Segment Information (Financial information by segment) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Equipment rentals									$ 4,949	$ 4,819	$ 4,196
Sales of rental equipment									538	544	490
Sales of new equipment									157	149	104
Contractor supplies sales									79	85	87
Service and other revenues									94	88	78
Total revenues	$ 1,523	$ 1,550	$ 1,429	$ 1,315	$ 1,564	$ 1,544	$ 1,399	$ 1,178	5,817	5,685	4,955
Depreciation and amortization expense									1,244	1,194	1,098
Gross profit	648	$ 690	$ 618	$ 524	707	$ 688	$ 589	$ 448	2,480	2,432	1,987
Capital expenditures									1,636	1,821	1,684
Total assets	12,083				12,129				12,083	12,129	10,876
Operating segments | General rentals
Segment Reporting Information [Line Items]
Equipment rentals									4,241	4,222	3,869
Sales of rental equipment									504	519	474
Sales of new equipment									137	113	97
Contractor supplies sales									67	73	79
Service and other revenues									83	75	72
Total revenues									5,032	5,002	4,591
Depreciation and amortization expense									1,071	1,060	1,038
Capital expenditures									1,439	1,594	1,556
Total assets	10,561				10,597				10,561	10,597	10,322
Operating segments | Trench, power and pump
Segment Reporting Information [Line Items]
Equipment rentals									708	597	327
Sales of rental equipment									34	25	16
Sales of new equipment									20	36	7
Contractor supplies sales									12	12	8
Service and other revenues									11	13	6
Total revenues									785	683	364
Depreciation and amortization expense									173	134	60
Capital expenditures									197	227	128
Total assets	$ 1,522				$ 1,532				1,522	1,532	554
Equipment rentals
Segment Reporting Information [Line Items]
Gross profit									2,147	2,092	1,710
Equipment rentals | Operating segments | General rentals
Segment Reporting Information [Line Items]
Gross profit									1,819	1,790	1,557
Equipment rentals | Operating segments | Trench, power and pump
Segment Reporting Information [Line Items]
Gross profit									$ 328	$ 302	$ 153