FAIR VALUE MEASUREMENTS - Fair Value Hierarchy Levels of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Assets:
Available for sale, fixed maturity securities	$ 105,882	$ 91,262
Equity securities	1,283	802
Other investments	1,139	628
Cash and cash equivalents	5,141	4,896
Asset derivatives	583	482
Total assets	114,028	98,070
Liabilities:
Liability derivatives	697	586
Total liabilities	697	586
Foreign currency swaps
Assets:
Asset derivatives	180	241
Liabilities:
Liability derivatives	312	204
Foreign currency forwards
Assets:
Asset derivatives	402	238
Liabilities:
Liability derivatives	385	377
Foreign currency options
Assets:
Asset derivatives	1
Liabilities:
Liability derivatives		5
Interest rate swaps
Assets:
Asset derivatives		3
Government and agencies
Assets:
Available for sale, fixed maturity securities	37,350	36,400
Municipalities
Assets:
Available for sale, fixed maturity securities	3,018	1,847
Mortgage- and asset-backed securities
Assets:
Available for sale, fixed maturity securities	1,038	410
Public utilities
Assets:
Available for sale, fixed maturity securities	10,817	6,780
Sovereign and supranational
Assets:
Available for sale, fixed maturity securities	1,382	1,042
Banks/financial institutions
Assets:
Available for sale, fixed maturity securities	12,060	10,287
Other corporate
Assets:
Available for sale, fixed maturity securities	40,217	34,496
Level 1
Assets:
Available for sale, fixed maturity securities	36,032	34,878
Equity securities	1,095	642
Other investments	1,139	628
Cash and cash equivalents	5,141	4,896
Asset derivatives	0	0
Total assets	43,407	41,044
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
Level 1 \| Interest rate swaps
Assets:
Asset derivatives		0
Level 1 \| Government and agencies
Assets:
Available for sale, fixed maturity securities	36,032	34,878
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	68,833	55,697
Equity securities	86	80
Other investments	0	0
Cash and cash equivalents	0	0
Asset derivatives	450	313
Total assets	69,369	56,090
Liabilities:
Total liabilities	466	460
Level 2 \| Foreign currency swaps
Assets:
Asset derivatives	47	72
Liabilities:
Liability derivatives	81	78
Level 2 \| Foreign currency forwards
Assets:
Asset derivatives	402	238
Liabilities:
Liability derivatives	385	377
Level 2 \| Foreign currency options
Assets:
Asset derivatives	1
Liabilities:
Liability derivatives		5
Level 2 \| Interest rate swaps
Assets:
Asset derivatives		3
Level 2 \| Government and agencies
Assets:
Available for sale, fixed maturity securities	1,318	1,522
Level 2 \| Municipalities
Assets:
Available for sale, fixed maturity securities	3,018	1,847
Level 2 \| Mortgage- and asset-backed securities
Assets:
Available for sale, fixed maturity securities	814	232
Level 2 \| Public utilities
Assets:
Available for sale, fixed maturity securities	10,395	6,556
Level 2 \| Sovereign and supranational
Assets:
Available for sale, fixed maturity securities	1,334	1,042
Level 2 \| Banks/financial institutions
Assets:
Available for sale, fixed maturity securities	12,036	10,264
Level 2 \| Other corporate
Assets:
Available for sale, fixed maturity securities	39,918	34,234
Level 3
Assets:
Available for sale, fixed maturity securities	1,017	687
Equity securities	102	80
Other investments	0	0
Cash and cash equivalents	0	0
Asset derivatives	133	169
Total assets	1,252	936
Liabilities:
Total liabilities	231	126
Level 3 \| Foreign currency swaps
Assets:
Asset derivatives	133	169
Liabilities:
Liability derivatives	231	126
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
Level 3 \| Interest rate swaps
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	224	178
Level 3 \| Public utilities
Assets:
Available for sale, fixed maturity securities	422	224
Level 3 \| Sovereign and supranational
Assets:
Available for sale, fixed maturity securities	48	0
Level 3 \| Banks/financial institutions
Assets:
Available for sale, fixed maturity securities	24	23
Level 3 \| Other corporate
Assets:
Available for sale, fixed maturity securities	$ 299	$ 262

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