Income taxes - Deferred income taxes (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Deferred income tax liabilities:
Investments, including unrealized appreciation	$ 47,158	$ 56,766
Deferred charges retroactive reinsurance	1,847	1,994
Property, plant and equipment and equipment held for lease	33,590	32,991
Goodwill and other intangible assets	7,498	7,546
Other	5,043	4,452
Deferred income tax liabilities	95,136	103,749
Deferred income tax assets:
Unpaid losses and loss adjustment expenses	1,226	1,255
Unearned premiums	1,284	1,285
Accrued liabilities	2,713	2,626
Regulatory liabilities	1,364	1,248
Deferred revenue	2,539	2,282
Other	2,447	2,709
Deferred income tax assets	11,573	11,405
Net deferred income tax liability	$ 83,563	$ 92,344