INVESTMENTS - Components of Net Investment Income (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									$ 3,334	$ 3,385	$ 3,230
Less investment expenses									114	107	95
Net investment income	$ 812	$ 811	$ 802	$ 794	$ 813	$ 842	$ 822	$ 801	3,220	3,278	3,135
Fixed-maturity securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									3,094	3,214	3,094
Perpetual securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									79	94	114
Equity securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									42	35	3
Other Investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									94	31	15
Short term investments and cash equivalents
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income									$ 25	$ 11	$ 4