Segment Information (Financial information by segment) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Equipment rentals									$ 5,715	$ 4,941	$ 4,949
Service and other revenues									118	102	94
Total revenues	$ 1,922	$ 1,766	$ 1,597	$ 1,356	$ 1,523	$ 1,508	$ 1,421	$ 1,310	6,641	5,762	5,817
Depreciation and amortization									1,383	1,245	1,244
Gross profit	827	$ 773	$ 655	$ 514	657	$ 656	$ 590	$ 500	2,769	2,403	2,480
Capital expenditures									1,889	1,339	1,636
Total assets	15,030				11,988				15,030	11,988	12,083
General rentals
Segment Reporting Information [Line Items]
Equipment rentals									4,727	4,166	4,241
Service and other revenues									105	91	83
Total revenues									5,565	4,908	5,032
Depreciation and amortization									1,188	1,066	1,071
Capital expenditures									1,675	1,189	1,439
Total assets	13,351				10,496				13,351	10,496	10,561
Trench, power and pump
Segment Reporting Information [Line Items]
Equipment rentals									988	775	708
Service and other revenues									13	11	11
Total revenues									1,076	854	785
Depreciation and amortization									195	179	173
Capital expenditures									214	150	197
Total assets	$ 1,679				$ 1,492				1,679	1,492	1,522
Rental Equipment
Segment Reporting Information [Line Items]
Sales revenue									550	496	538
Rental Equipment | General rentals
Segment Reporting Information [Line Items]
Sales revenue									509	459	504
Rental Equipment | Trench, power and pump
Segment Reporting Information [Line Items]
Sales revenue									41	37	34
New Equipment
Segment Reporting Information [Line Items]
Sales revenue									178	144	157
New Equipment | General rentals
Segment Reporting Information [Line Items]
Sales revenue									159	128	137
New Equipment | Trench, power and pump
Segment Reporting Information [Line Items]
Sales revenue									19	16	20
Contractor Supplies
Segment Reporting Information [Line Items]
Sales revenue									80	79	79
Contractor Supplies | General rentals
Segment Reporting Information [Line Items]
Sales revenue									65	64	67
Contractor Supplies | Trench, power and pump
Segment Reporting Information [Line Items]
Sales revenue									15	15	12
Equipment Rentals, Operating Lease
Segment Reporting Information [Line Items]
Gross profit									2,440	2,089	2,147
Equipment Rentals, Operating Lease | General rentals
Segment Reporting Information [Line Items]
Gross profit									1,950	1,725	1,819
Equipment Rentals, Operating Lease | Trench, power and pump
Segment Reporting Information [Line Items]
Gross profit									$ 490	$ 364	$ 328