FAIR VALUE MEASUREMENTS - Fair Value Hierarchy Levels of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Assets:
Available for sale, fixed maturity securities	$ 102,284	$ 105,882
Equity securities	1,475	1,283
Other investments	1,667	1,139
Cash and cash equivalents	5,469	5,141
Asset derivatives	739	583
Total assets	111,634	114,028
Liabilities:
Liability derivatives	1,096	697
Total liabilities	1,096	697
Foreign currency swaps
Assets:
Asset derivatives	169	180
Liabilities:
Liability derivatives	332	312
Foreign currency forwards
Assets:
Asset derivatives	567	402
Liabilities:
Liability derivatives	762	385
Foreign currency options
Assets:
Asset derivatives	1	1
Liabilities:
Liability derivatives	1
Interest rate swaps
Assets:
Asset derivatives	1
Liabilities:
Liability derivatives	1
Forward bond purchase commitment
Assets:
Asset derivatives	1
Government and agencies
Assets:
Available for sale, fixed maturity securities	35,682	37,350
Municipalities
Assets:
Available for sale, fixed maturity securities	2,965	3,018
Mortgage- and asset-backed securities
Assets:
Available for sale, fixed maturity securities	1,284	1,038
Public utilities
Assets:
Available for sale, fixed maturity securities	10,393	10,817
Sovereign and supranational
Assets:
Available for sale, fixed maturity securities	1,258	1,382
Banks/financial institutions
Assets:
Available for sale, fixed maturity securities	11,904	12,060
Other corporate
Assets:
Available for sale, fixed maturity securities	38,798	40,217
Level 1
Assets:
Available for sale, fixed maturity securities	34,344	36,032
Equity securities	1,231	1,095
Other investments	1,667	1,139
Cash and cash equivalents	5,469	5,141
Asset derivatives	0	0
Total assets	42,711	43,407
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	0
Liabilities:
Liability derivatives	0
Level 1 | Interest rate swaps
Assets:
Asset derivatives	0
Liabilities:
Liability derivatives	0
Level 1 | Forward bond purchase commitment
Assets:
Asset derivatives	0
Level 1 | Government and agencies
Assets:
Available for sale, fixed maturity securities	34,344	36,032
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	66,803	68,833
Equity securities	86	86
Other investments	0	0
Cash and cash equivalents	0	0
Asset derivatives	629	450
Total assets	67,518	69,369
Liabilities:
Total liabilities	786	466
Level 2 | Foreign currency swaps
Assets:
Asset derivatives	59	47
Liabilities:
Liability derivatives	22	81
Level 2 | Foreign currency forwards
Assets:
Asset derivatives	567	402
Liabilities:
Liability derivatives	762	385
Level 2 | Foreign currency options
Assets:
Asset derivatives	1	1
Liabilities:
Liability derivatives	1
Level 2 | Interest rate swaps
Assets:
Asset derivatives	1
Liabilities:
Liability derivatives	1
Level 2 | Forward bond purchase commitment
Assets:
Asset derivatives	1
Level 2 | Government and agencies
Assets:
Available for sale, fixed maturity securities	1,338	1,318
Level 2 | Municipalities
Assets:
Available for sale, fixed maturity securities	2,965	3,018
Level 2 | Mortgage- and asset-backed securities
Assets:
Available for sale, fixed maturity securities	1,026	814
Level 2 | Public utilities
Assets:
Available for sale, fixed maturity securities	9,913	10,395
Level 2 | Sovereign and supranational
Assets:
Available for sale, fixed maturity securities	1,213	1,334
Level 2 | Banks/financial institutions
Assets:
Available for sale, fixed maturity securities	11,866	12,036
Level 2 | Other corporate
Assets:
Available for sale, fixed maturity securities	38,482	39,918
Level 3
Assets:
Available for sale, fixed maturity securities	1,137	1,017
Equity securities	158	102
Other investments	0	0
Cash and cash equivalents	0	0
Asset derivatives	110	133
Total assets	1,405	1,252
Liabilities:
Total liabilities	310	231
Level 3 | Foreign currency swaps
Assets:
Asset derivatives	110	133
Liabilities:
Liability derivatives	310	231
Level 3 | Foreign currency forwards
Assets:
Asset derivatives	0	0
Liabilities:
Liability derivatives	0	0
Level 3 | Foreign currency options
Assets:
Asset derivatives	0	0
Liabilities:
Liability derivatives	0
Level 3 | Interest rate swaps
Assets:
Asset derivatives	0
Liabilities:
Liability derivatives	0
Level 3 | Forward bond purchase commitment
Assets:
Asset derivatives	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	258	224
Level 3 | Public utilities
Assets:
Available for sale, fixed maturity securities	480	422
Level 3 | Sovereign and supranational
Assets:
Available for sale, fixed maturity securities	45	48
Level 3 | Banks/financial institutions
Assets:
Available for sale, fixed maturity securities	38	24
Level 3 | Other corporate
Assets:
Available for sale, fixed maturity securities	$ 316	$ 299