FAIR VALUE MEASUREMENTS - Fair Value Hierarchy Levels of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions		Dec. 31, 2018		Dec. 31, 2017
Assets:
Available for sale, fixed maturity securities	[2],[3]	$ 82,895	[1],[4]	$ 84,313	[5]
Equity securities	[2],[3],[6]	987
Equity securities, available-for-sale				1,023
Other investments		152		57
Cash and cash equivalents		4,337		3,491
Asset derivatives		417		331
Total assets		88,788		89,215
Liabilities:
Liability derivatives		387		474
Total liabilities		387		474
Foreign currency swaps
Assets:
Asset derivatives		285		296
Liabilities:
Liability derivatives		234		197
Foreign currency forwards
Assets:
Asset derivatives		126		22
Liabilities:
Liability derivatives		151		274
Foreign currency options
Assets:
Asset derivatives		3		12
Liabilities:
Liability derivatives		1		3
Interest rate swaptions
Liabilities:
Liability derivatives		1
Interest rate swaps
Assets:
Asset derivatives		3
Credit default swaps
Assets:
Asset derivatives				1
Government and agencies
Assets:
Available for sale, fixed maturity securities		34,342		31,230
Municipalities
Assets:
Available for sale, fixed maturity securities		1,863		1,370
Mortgage- and asset-backed securities
Assets:
Available for sale, fixed maturity securities		339		444
Public utilities
Assets:
Available for sale, fixed maturity securities		7,171		7,954
Sovereign and supranational
Assets:
Available for sale, fixed maturity securities		1,260		1,909
Banks/financial institutions
Assets:
Available for sale, fixed maturity securities		8,918		8,933
Other corporate
Assets:
Available for sale, fixed maturity securities		29,002		32,473
Level 1
Assets:
Available for sale, fixed maturity securities		32,993		30,109
Equity securities		874
Equity securities, available-for-sale				1,001
Other investments		152		57
Cash and cash equivalents		4,337		3,491
Asset derivatives		0		0
Total assets		38,356		34,658
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		0
Level 1 | Interest rate swaptions
Liabilities:
Liability derivatives		0
Level 1 | Interest rate swaps
Assets:
Asset derivatives		0
Level 1 | Credit default swaps
Assets:
Asset derivatives				0
Level 1 | Government and agencies
Assets:
Available for sale, fixed maturity securities		32,993		30,109
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		49,380		53,790
Equity securities		67
Equity securities, available-for-sale				6
Other investments		0		0
Cash and cash equivalents		0		0
Asset derivatives		235		180
Total assets		49,682		53,976
Liabilities:
Total liabilities		285		346
Level 2 | Foreign currency swaps
Assets:
Asset derivatives		103		146
Liabilities:
Liability derivatives		132		69
Level 2 | Foreign currency forwards
Assets:
Asset derivatives		126		22
Liabilities:
Liability derivatives		151		274
Level 2 | Foreign currency options
Assets:
Asset derivatives		3		12
Liabilities:
Liability derivatives		1		3
Level 2 | Interest rate swaptions
Liabilities:
Liability derivatives		1
Level 2 | Interest rate swaps
Assets:
Asset derivatives		3
Level 2 | Credit default swaps
Assets:
Asset derivatives				0
Level 2 | Government and agencies
Assets:
Available for sale, fixed maturity securities		1,349		1,121
Level 2 | Municipalities
Assets:
Available for sale, fixed maturity securities		1,863		1,370
Level 2 | Mortgage- and asset-backed securities
Assets:
Available for sale, fixed maturity securities		162		269
Level 2 | Public utilities
Assets:
Available for sale, fixed maturity securities		7,062		7,886
Level 2 | Sovereign and supranational
Assets:
Available for sale, fixed maturity securities		1,260		1,909
Level 2 | Banks/financial institutions
Assets:
Available for sale, fixed maturity securities		8,895		8,908
Level 2 | Other corporate
Assets:
Available for sale, fixed maturity securities		28,789		32,327
Level 3
Assets:
Available for sale, fixed maturity securities		522		414
Equity securities		46
Equity securities, available-for-sale				16
Other investments		0		0
Cash and cash equivalents		0		0
Asset derivatives		182		151
Total assets		750		581
Liabilities:
Total liabilities		102		128
Level 3 | Foreign currency swaps
Assets:
Asset derivatives		182		150
Liabilities:
Liability derivatives		102		128
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		0
Level 3 | Interest rate swaptions
Liabilities:
Liability derivatives		0
Level 3 | Interest rate swaps
Assets:
Asset derivatives		0
Level 3 | Credit default swaps
Assets:
Asset derivatives				1
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		177		175
Level 3 | Public utilities
Assets:
Available for sale, fixed maturity securities		109		68
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		25
Level 3 | Other corporate
Assets:
Available for sale, fixed maturity securities		$ 213		$ 146

[1] Includes perpetual securities ($1,139 at amortized cost and $1,140 at fair value)

[2] Includes perpetual securities

[3] Includes perpetual securities

[4] Includes perpetual securities, categorized in accordance with their respective economic maturities (the expected maturity date created by the combination of features in the financial instrument)

[5] Includes perpetual securities ($1,462 at amortized cost and $1,789 at fair value)

[6] Includes perpetual securities ($62 at fair value)