INVESTMENTS - Components of Net Investment Income (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									$ 3,755	$ 3,590	$ 3,334
Less investment expenses									177	148	114
Net investment income	$ 886	$ 936	$ 878	$ 878	$ 874	$ 870	$ 862	$ 837	3,578	3,442	3,220
Fixed maturity securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									3,141	3,142	3,173
Equity securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									37	38	42
Commercial mortgage and other loans
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									468	333	86
Other investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									53	36	8
Short-term investments and cash equivalents
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									$ 56	$ 41	$ 25