INVESTMENTS - Components of Net Investment Income (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									$ 3,850	$ 3,755	$ 3,590
Less investment expenses									212	177	148
Net investment income	$ 968	$ 896	$ 870	$ 904	$ 886	$ 936	$ 878	$ 878	3,638	3,578	3,442
Fixed maturity securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									3,113	3,141	3,142
Equity securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									29	37	38
Commercial mortgage and other loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									545	468	333
Other investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									145	53	36
Short-term investments and cash equivalents
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									$ 18	$ 56	$ 41