Income taxes - Deferred taxes (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred tax liabilities:
Investments – unrealized appreciation and cost basis differences	$ 32,134	$ 17,765
Deferred charges reinsurance assumed	2,890	2,970
Property, plant and equipment and equipment held for lease	29,388	28,279
Goodwill and other intangible assets	7,293	7,199
Other	3,144	3,187
Deferred tax liabilities	74,849	59,400
Deferred tax assets:
Unpaid losses and loss adjustment expenses	(1,086)	(1,238)
Unearned premiums	(853)	(767)
Accrued liabilities	(1,981)	(1,956)
Regulatory liabilities	(1,610)	(1,673)
Other	(3,496)	(3,263)
Deferred tax assets	(9,026)	(8,897)
Net deferred tax liability	$ 65,823	$ 50,503