Income Taxes - Summary of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Property and casualty claim and claim adjustment expense reserves	$ 129	$ 108
Unearned premium reserves	153	108
Receivables	11	13
Employee benefits	212	222
Deferred retroactive reinsurance benefit	82	79
Net operating loss carryforwards	275	251
Tax credit carryforwards	47	101
Net unrealized losses		24
Basis differential in investment in subsidiary	8	8
Disallowed interest deduction	41	16
Other	179	181
Total deferred tax assets	1,137	1,111
Valuation allowance	(187)	(175)
Net deferred tax assets	950	936
Deferred tax liabilities:
Deferred acquisition costs	(83)	(78)
Net unrealized gains	(263)
Property, plant and equipment	(848)	(840)
Basis differential in investment in subsidiary	(679)	(586)
Other liabilities	(208)	(236)
Total deferred tax liabilities	(2,081)	(1,740)
Net deferred tax liabilities	$ (1,131)	$ (804)