INVESTMENTS - Components of Net Investment Income (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									$ 3,590	$ 3,334	$ 3,385
Less investment expenses									148	114	107
Net investment income	$ 874	$ 870	$ 862	$ 837	$ 812	$ 811	$ 802	$ 794	3,442	3,220	3,278
Fixed maturity securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									3,142	3,173	3,308
Equity securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									38	42	35
Other investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									369	94	31
Short-term investments and cash equivalents
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									$ 41	$ 25	$ 11