Description of Business, Basis of Presentation, and Significant Accounting Policies - Consolidated Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended								6 Months Ended		9 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	Jun. 30, 2024	Jun. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Operating activities
Net income	$ 108	$ 198	$ 219	$ 143	$ 62	$ 285	$ 311	$ 299	$ 362	$ 610	$ 560	$ 895	$ 668	$ 957	$ 1,714
Reconciliation of net income to net cash provided by operating activities
Depreciation and amortization				310				316	582	608	864	912	1,199	1,227	1,327
Net change in
Deferred income taxes				50				(26)	117	(51)	218	73	436	81	(553)
Net cash provided by operating activities				1,266				1,413	2,720	2,975	3,577	4,609	4,528	4,557	6,247
Investing activities
Disposals of operating lease assets				964				725	2,164	1,625	3,113	2,455	3,808	3,228	3,023
Net cash provided by (used in) investing activities				3,576				(363)	2,590	(2,435)	3,785	(4,144)	$ 4,991	(7,182)	$ (17,263)
As Originally Reported
Operating activities
Net income		$ 357	$ 294	157	$ 76	$ 296	$ 329	319	451	648	808	944		1,020
Reconciliation of net income to net cash provided by operating activities
Depreciation and amortization				322				317	616	613	930	923		1,247
Net change in
Deferred income taxes				1				(24)	44	(53)	201	62		58
Net cash provided by operating activities				1,341				1,432	2,916	3,020	3,908	4,680		4,663
Investing activities
Disposals of operating lease assets				889				706	1,968	1,580	2,782	2,384		3,122
Net cash provided by (used in) investing activities				$ 3,501				$ (382)	$ 2,394	$ (2,480)	$ 3,454	$ (4,215)		(7,288)
Adjustments
Operating activities
Net income														(63)
Reconciliation of net income to net cash provided by operating activities
Depreciation and amortization														(20)
Net change in
Deferred income taxes														23
Net cash provided by operating activities														(106)
Investing activities
Disposals of operating lease assets														106
Net cash provided by (used in) investing activities														$ 106