FAIR VALUE MEASUREMENTS - Fair Value Hierarchy Levels of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Assets:
Available for sale, fixed maturity securities	$ 87,924	$ 82,895
Equity securities	1,041	987
Other investments	543	152
Cash and cash equivalents	3,892	4,337
Asset derivatives	401	417
Total assets	93,801	88,788
Liabilities:
Liability derivatives	365	387
Total liabilities	365	387
Foreign currency swaps
Assets:
Asset derivatives	274	285
Liabilities:
Liability derivatives	206	234
Foreign currency forwards
Assets:
Asset derivatives	119	126
Liabilities:
Liability derivatives	156	151
Foreign currency options
Assets:
Asset derivatives		3
Liabilities:
Liability derivatives	2	1
Interest rate swaps
Assets:
Asset derivatives	8	3
Interest rate swaptions
Liabilities:
Liability derivatives	1	1
Government and agencies
Assets:
Available for sale, fixed maturity securities	36,249	34,342
Municipalities
Assets:
Available for sale, fixed maturity securities	1,908	1,863
Mortgage- and asset-backed securities
Assets:
Available for sale, fixed maturity securities	414	339
Public utilities
Assets:
Available for sale, fixed maturity securities	6,497	7,171
Sovereign and supranational
Assets:
Available for sale, fixed maturity securities	1,154	1,260
Banks/financial institutions
Assets:
Available for sale, fixed maturity securities	9,391	8,918
Other corporate
Assets:
Available for sale, fixed maturity securities	32,311	29,002
Level 1
Assets:
Available for sale, fixed maturity securities	34,727	32,993
Equity securities	925	874
Other investments	543	152
Cash and cash equivalents	3,892	4,337
Asset derivatives	0	0
Total assets	40,087	38,356
Liabilities:
Total liabilities	0	0
Level 1 | Foreign currency swaps
Assets:
Asset derivatives	0	0
Liabilities:
Liability derivatives	0	0
Level 1 | Foreign currency forwards
Assets:
Asset derivatives	0	0
Liabilities:
Liability derivatives	0	0
Level 1 | Foreign currency options
Assets:
Asset derivatives		0
Liabilities:
Liability derivatives	0	0
Level 1 | Interest rate swaps
Assets:
Asset derivatives	0	0
Level 1 | Interest rate swaptions
Liabilities:
Liability derivatives	0	0
Level 1 | Government and agencies
Assets:
Available for sale, fixed maturity securities	34,727	32,993
Level 1 | Municipalities
Assets:
Available for sale, fixed maturity securities	0	0
Level 1 | Mortgage- and asset-backed securities
Assets:
Available for sale, fixed maturity securities	0	0
Level 1 | Public utilities
Assets:
Available for sale, fixed maturity securities	0	0
Level 1 | Sovereign and supranational
Assets:
Available for sale, fixed maturity securities	0	0
Level 1 | Banks/financial institutions
Assets:
Available for sale, fixed maturity securities	0	0
Level 1 | Other corporate
Assets:
Available for sale, fixed maturity securities	0	0
Level 2
Assets:
Available for sale, fixed maturity securities	52,627	49,380
Equity securities	70	67
Other investments	0	0
Cash and cash equivalents	0	0
Asset derivatives	223	235
Total assets	52,920	49,682
Liabilities:
Total liabilities	257	285
Level 2 | Foreign currency swaps
Assets:
Asset derivatives	96	103
Liabilities:
Liability derivatives	98	132
Level 2 | Foreign currency forwards
Assets:
Asset derivatives	119	126
Liabilities:
Liability derivatives	156	151
Level 2 | Foreign currency options
Assets:
Asset derivatives		3
Liabilities:
Liability derivatives	2	1
Level 2 | Interest rate swaps
Assets:
Asset derivatives	8	3
Level 2 | Interest rate swaptions
Liabilities:
Liability derivatives	1	1
Level 2 | Government and agencies
Assets:
Available for sale, fixed maturity securities	1,522	1,349
Level 2 | Municipalities
Assets:
Available for sale, fixed maturity securities	1,908	1,863
Level 2 | Mortgage- and asset-backed securities
Assets:
Available for sale, fixed maturity securities	236	162
Level 2 | Public utilities
Assets:
Available for sale, fixed maturity securities	6,412	7,062
Level 2 | Sovereign and supranational
Assets:
Available for sale, fixed maturity securities	1,154	1,260
Level 2 | Banks/financial institutions
Assets:
Available for sale, fixed maturity securities	9,368	8,895
Level 2 | Other corporate
Assets:
Available for sale, fixed maturity securities	32,027	28,789
Level 3
Assets:
Available for sale, fixed maturity securities	570	522
Equity securities	46	46
Other investments	0	0
Cash and cash equivalents	0	0
Asset derivatives	178	182
Total assets	794	750
Liabilities:
Total liabilities	108	102
Level 3 | Foreign currency swaps
Assets:
Asset derivatives	178	182
Liabilities:
Liability derivatives	108	102
Level 3 | Foreign currency forwards
Assets:
Asset derivatives	0	0
Liabilities:
Liability derivatives	0	0
Level 3 | Foreign currency options
Assets:
Asset derivatives		0
Liabilities:
Liability derivatives	0	0
Level 3 | Interest rate swaps
Assets:
Asset derivatives	0	0
Level 3 | Interest rate swaptions
Liabilities:
Liability derivatives	0	0
Level 3 | Government and agencies
Assets:
Available for sale, fixed maturity securities	0	0
Level 3 | Municipalities
Assets:
Available for sale, fixed maturity securities	0	0
Level 3 | Mortgage- and asset-backed securities
Assets:
Available for sale, fixed maturity securities	178	177
Level 3 | Public utilities
Assets:
Available for sale, fixed maturity securities	85	109
Level 3 | Sovereign and supranational
Assets:
Available for sale, fixed maturity securities	0	0
Level 3 | Banks/financial institutions
Assets:
Available for sale, fixed maturity securities	23	23
Level 3 | Other corporate
Assets:
Available for sale, fixed maturity securities	$ 284	$ 213