FAIR VALUE MEASUREMENTS - Fair Value Hierarchy Levels of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Assets:
Available for sale, fixed maturity securities	$ 100,722	$ 105,882
Equity securities	1,461	1,283
Other investments	1,833	1,139
Cash and cash equivalents	6,208	5,141
Asset derivatives	745	583
Total assets	110,969	114,028
Liabilities:
Liability derivatives	1,270	697
Total liabilities	1,270	697
Foreign currency swaps
Assets:
Asset derivatives	151	180
Liabilities:
Liability derivatives	378	312
Foreign currency forwards
Assets:
Asset derivatives	593	402
Liabilities:
Liability derivatives	875	385
Foreign currency options
Assets:
Asset derivatives	1	1
Interest rate swaps
Liabilities:
Liability derivatives	16
Forward bond purchase commitment
Liabilities:
Liability derivatives	1
Government and agencies
Assets:
Available for sale, fixed maturity securities	35,226	37,350
Municipalities
Assets:
Available for sale, fixed maturity securities	2,937	3,018
Mortgage- and asset-backed securities
Assets:
Available for sale, fixed maturity securities	1,292	1,038
Public utilities
Assets:
Available for sale, fixed maturity securities	10,315	10,817
Sovereign and supranational
Assets:
Available for sale, fixed maturity securities	1,142	1,382
Banks/financial institutions
Assets:
Available for sale, fixed maturity securities	11,742	12,060
Other corporate
Assets:
Available for sale, fixed maturity securities	38,068	40,217
Level 1
Assets:
Available for sale, fixed maturity securities	33,903	36,032
Equity securities	1,210	1,095
Other investments	1,833	1,139
Cash and cash equivalents	6,208	5,141
Asset derivatives	0	0
Total assets	43,154	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
Level 1 | Interest rate swaps
Liabilities:
Liability derivatives	0
Level 1 | Forward bond purchase commitment
Liabilities:
Liability derivatives	0
Level 1 | Government and agencies
Assets:
Available for sale, fixed maturity securities	33,903	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	65,649	68,833
Equity securities	90	86
Other investments	0	0
Cash and cash equivalents	0	0
Asset derivatives	646	450
Total assets	66,385	69,369
Liabilities:
Total liabilities	914	466
Level 2 | Foreign currency swaps
Assets:
Asset derivatives	52	47
Liabilities:
Liability derivatives	22	81
Level 2 | Foreign currency forwards
Assets:
Asset derivatives	593	402
Liabilities:
Liability derivatives	875	385
Level 2 | Foreign currency options
Assets:
Asset derivatives	1	1
Level 2 | Interest rate swaps
Liabilities:
Liability derivatives	16
Level 2 | Forward bond purchase commitment
Liabilities:
Liability derivatives	1
Level 2 | Government and agencies
Assets:
Available for sale, fixed maturity securities	1,323	1,318
Level 2 | Municipalities
Assets:
Available for sale, fixed maturity securities	2,937	3,018
Level 2 | Mortgage- and asset-backed securities
Assets:
Available for sale, fixed maturity securities	1,042	814
Level 2 | Public utilities
Assets:
Available for sale, fixed maturity securities	9,792	10,395
Level 2 | Sovereign and supranational
Assets:
Available for sale, fixed maturity securities	1,097	1,334
Level 2 | Banks/financial institutions
Assets:
Available for sale, fixed maturity securities	11,696	12,036
Level 2 | Other corporate
Assets:
Available for sale, fixed maturity securities	37,762	39,918
Level 3
Assets:
Available for sale, fixed maturity securities	1,170	1,017
Equity securities	161	102
Other investments	0	0
Cash and cash equivalents	0	0
Asset derivatives	99	133
Total assets	1,430	1,252
Liabilities:
Total liabilities	356	231
Level 3 | Foreign currency swaps
Assets:
Asset derivatives	99	133
Liabilities:
Liability derivatives	356	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
Level 3 | Interest rate swaps
Liabilities:
Liability derivatives	0
Level 3 | Forward bond purchase commitment
Liabilities:
Liability 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	250	224
Level 3 | Public utilities
Assets:
Available for sale, fixed maturity securities	523	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	46	24
Level 3 | Other corporate
Assets:
Available for sale, fixed maturity securities	$ 306	$ 299