Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Nov. 30, 2022
Selected Quarterly Financial Information [Abstract]
Revenues	$ 3,728	$ 3,765	$ 3,554	$ 3,285	$ 3,296	$ 3,051	$ 2,771	$ 2,524	$ 14,332	$ 11,642	$ 9,716
Gross profit	1,562	1,585	1,425	1,241	1,488	1,366	1,150	992	5,813	4,996	3,853
Operating income	1,063	1,099	925	740	1,024	921	715	572	3,827	3,232	2,277
Net income	$ 679	$ 703	$ 591	$ 451	$ 639	$ 606	$ 493	$ 367	$ 2,424	$ 2,105	$ 1,386
Earnings per share - basic (in dollars per share)	$ 10.04	$ 10.30	$ 8.60	$ 6.50	$ 9.20	$ 8.69	$ 6.91	$ 5.07	$ 35.40	$ 29.77	$ 19.14
Earnings per share - diluted (in dollars per share)	10.01	10.29	8.58	6.47	9.15	8.66	6.90	5.05	35.28	29.65	$ 19.04
Effect of Fourth Quarter Events [Line Items]
Merger related intangible asset amortization (in dollars per share)	(0.52)	(0.57)	(0.55)	(0.70)	(0.39)	(0.44)	(0.45)	(0.52)	(2.33)	(1.79)
Impact on depreciation related to acquired fleet and property and equipment (in dollars per share)	(0.44)	(0.59)	(0.30)	(0.32)	(0.08)	(0.12)	(0.26)	(0.10)	(1.65)	(0.56)
Impact of the fair value mark-up of acquired fleet (in dollars per share)	(0.25)	(0.23)	(0.25)	(0.44)	(0.12)	(0.05)	(0.05)	(0.06)	(1.17)	(0.29)
Restructuring charge (in dollars per share)	$ (0.04)	$ (0.05)	$ (0.20)	$ (0.02)	0	0.01	0	0	$ (0.31)	0
Asset impairment charge (in dollars per share)					0	(0.01)	(0.02)	0		(0.03)
Loss on repurchase/redemption of debt securities (in dollars per share)					$ 0	$ 0	$ (0.18)	$ 0		$ (0.18)
Acquisition company revenue prior to acquisition	$ 200								$ 200
Senior notes | 6 percent Senior Secured Notes due 2029
Effect of Fourth Quarter Events [Line Items]
Debt instrument, face amount					$ 1,500					$ 1,500		$ 1,500
Stated interest rate	600.00%								600.00%			6.00%