Quarterly Financial Information (Unaudited) (Details) - USD ($)	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
Selected Quarterly Financial Information [Abstract]
Total revenues	$ 1,922,000,000	$ 1,766,000,000	$ 1,597,000,000	$ 1,356,000,000	$ 1,523,000,000	$ 1,508,000,000	$ 1,421,000,000	$ 1,310,000,000	$ 6,641,000,000	$ 5,762,000,000	$ 5,817,000,000
Gross profit	827,000,000	773,000,000	655,000,000	514,000,000	657,000,000	656,000,000	590,000,000	500,000,000	2,769,000,000	2,403,000,000	2,480,000,000
Operating income	462,000,000	448,000,000	340,000,000	257,000,000	402,000,000	412,000,000	347,000,000	254,000,000	1,507,000,000	1,415,000,000	1,518,000,000
Net income	$ 897,000,000	$ 199,000,000	$ 141,000,000	$ 109,000,000	$ 153,000,000	$ 187,000,000	$ 134,000,000	$ 92,000,000	$ 1,346,000,000	$ 566,000,000	$ 585,000,000
Earnings per share - basic (in dollars per share)	$ 10.60	$ 2.36	$ 1.67	$ 1.29	$ 1.82	$ 2.18	$ 1.52	$ 1.01	$ 15.91	$ 6.49	$ 6.14
Earnings per share - diluted (in dollars per share)	$ 10.45	2.33	1.65	1.27	1.80	2.16	1.52	1.01	$ 15.73	$ 6.45	$ 6.07
Effect of Fourth Quarter Events [Line Items]
Benefit of Tax Cuts and Jobs Act of 2017	$ 689,000,000								$ 689,000,000
Effect on Tax Cuts and Jobs Act of 2017 on diluted earnings per share (in dollars per share)	$ 8.03								$ 8.05
Merger related costs	$ 18,000,000								$ 50,000,000	$ 0	$ (26,000,000)
Restructuring charge	22,000,000								50,000,000	14,000,000	6,000,000
Loss on extinguishment of debt									$ 54,000,000	$ 101,000,000	123,000,000
Increase in stock compensation, net	$ 11,000,000
Earnings Per Share, Diluted, Other Disclosures [Abstract]
Merger related costs (in dollars per share)	$ (0.13)	(0.12)	(0.09)	(0.02)					$ (0.36)
Merger related intangible asset amortization (in dollars per share)	(0.32)	(0.27)	(0.30)	(0.28)	(0.29)	(0.28)	(0.28)	(0.30)	(1.15)	$ (1.12)
Impact on depreciation related to acquired fleet and property and equipment (in dollars per share)	(0.01)	(0.07)	0.03	0.00					(0.05)
Impact of the fair value mark-up of acquired fleet (in dollars per share)	(0.23)	(0.17)	(0.13)	(0.06)	(0.06)	(0.05)	(0.06)	(0.06)	(0.59)	(0.25)
Impact on interest expense related to fair value adjustment of acquired RSC indebtedness (in dollars per share)					0.00	0.00	0.00	0.00		0.01
Restructuring charge (in dollars per share)	(0.15)	(0.07)	(0.14)	0.00	(0.05)	(0.02)	(0.02)	(0.01)	(0.36)	(0.11)
Asset impairment charge (in dollars per share)	0.00	0.00	0.00	0.00	0.00	0.00	0.00	(0.02)	(0.01)	(0.03)
Loss on extinguishment of debt securities and amendment of ABL facility (in dollars per share)	$ (0.08)	$ (0.22)	$ (0.09)	$ 0.00	$ (0.47)	$ (0.07)	$ (0.18)	$ 0.00	$ (0.39)	$ (0.70)
Senior notes | 7 5/8 percent Senior Notes
Effect of Fourth Quarter Events [Line Items]
Redemption of principal amount of debt	$ 225,000,000				$ 850,000,000				$ 225,000,000	$ 850,000,000
Stated interest rate	7.625%				7.625%				7.625%	7.625%
Loss on extinguishment of debt	$ 11,000,000				$ 65,000,000
Senior notes | 5 1/2 percent Senior Notes due 2025
Effect of Fourth Quarter Events [Line Items]
Debt instrument, face amount					$ 750,000,000					$ 750,000,000
Stated interest rate	5.50%				5.50%				5.50%	5.50%
Closed Restructuring Programs
Effect of Fourth Quarter Events [Line Items]
Restructuring charge					$ 6,000,000				$ 2,000,000	$ 14,000,000	$ 6,000,000