Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Selected Quarterly Financial Information [Abstract]
Total revenues	$ 4,095	$ 3,992	$ 3,773	$ 3,485	$ 3,728	$ 3,765	$ 3,554	$ 3,285	$ 15,345	$ 14,332	$ 11,642
Gross profit	1,638	1,648	1,518	1,346	1,562	1,585	1,425	1,241	6,150	5,813	4,996
Operating income	1,087	1,122	1,004	852	1,063	1,099	925	740	4,065	3,827	3,232
Net income	$ 689	$ 708	$ 636	$ 542	$ 679	$ 703	$ 591	$ 451	$ 2,575	$ 2,424	$ 2,105
Earnings per share - basic (in dollars per share)	$ 10.50	$ 10.73	$ 9.56	$ 8.06	$ 10.04	$ 10.30	$ 8.60	$ 6.50	$ 38.82	$ 35.40	$ 29.77
Earnings per share - diluted (in dollars per share)	10.47	10.70	9.54	8.04	10.01	10.29	8.58	6.47	38.69	35.28	$ 29.65
Merger related intangible asset amortization (in dollars per share)	(0.55)	(0.53)	(0.58)	(0.49)	(0.52)	(0.57)	(0.55)	(0.70)	(2.14)	(2.33)
Impact on depreciation related to acquired fleet and property and equipment (in dollars per share)	(0.36)	(0.38)	(0.39)	(0.40)	(0.44)	(0.59)	(0.30)	(0.32)	(1.53)	(1.65)
Impact of the fair value mark-up of acquired fleet (in dollars per share)	(0.19)	(0.15)	(0.18)	(0.19)	(0.25)	(0.23)	(0.25)	(0.44)	(0.71)	(1.17)
Restructuring charge (in dollars per share)	(0.01)	(0.01)	(0.01)	(0.01)	$ (0.04)	$ (0.05)	$ (0.20)	$ (0.02)	(0.04)	$ (0.31)
Asset impairment charge (in dollars per share)	(0.01)	(0.03)	0	(0.01)					(0.05)
Loss on repurchase/redemption/amendment of debt (in dollars per share)	$ 0	$ 0	$ 0	$ (0.01)					$ (0.01)
Acquisition company revenue prior to acquisition	$ 200								$ 200