FAIR VALUE MEASUREMENTS - Fair Value Hierarchy Levels of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions		Mar. 31, 2018		Dec. 31, 2017
Assets:
Available-for-sale securities	[1]	$ 89,033	[2]	$ 84,313	[3]
Equity securities	[1],[4]	1,108
Asset derivatives		797		331
Other Investments				57
Cash and cash equivalents		4,080		3,491
Total assets		95,018		89,215
Liabilities:
Liability derivatives		353		474
Total liabilities		353		474
Foreign currency swaps
Assets:
Asset derivatives		370		296
Liabilities:
Liability derivatives		265		197
Foreign currency forwards
Assets:
Asset derivatives		426		22
Liabilities:
Liability derivatives		85		274
Foreign currency options
Assets:
Asset derivatives				12
Liabilities:
Liability derivatives		3		3
Credit default swaps
Assets:
Asset derivatives		1		1
Fixed maturities
Assets:
Available-for-sale securities	[1]	89,033		84,313
Fixed maturities | Government and agencies
Assets:
Available-for-sale securities		36,736		31,230
Fixed maturities | Municipalities
Assets:
Available-for-sale securities		1,373		1,370
Fixed maturities | Mortgage- and asset-backed securities
Assets:
Available-for-sale securities		455		444
Fixed maturities | Public utilities
Assets:
Available-for-sale securities		7,807		7,954
Fixed maturities | Sovereign and supranational
Assets:
Available-for-sale securities		1,866		1,909
Fixed maturities | Banks/financial institutions
Assets:
Available-for-sale securities		9,144		8,933
Fixed maturities | Other corporate
Assets:
Available-for-sale securities		31,652		32,473
Equity securities
Assets:
Available-for-sale securities				1,023
Level 1
Assets:
Available-for-sale securities		35,325		30,109
Equity securities		1,015
Asset derivatives		0		0
Other Investments				57
Cash and cash equivalents		4,080		3,491
Total assets		40,420		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
Liabilities:
Liability derivatives		0		0
Level 1 | Credit default swaps
Assets:
Asset derivatives		0		0
Level 1 | Fixed maturities
Assets:
Available-for-sale securities		35,325		30,109
Level 1 | Fixed maturities | Government and agencies
Assets:
Available-for-sale securities		35,325		30,109
Level 1 | Fixed maturities | Municipalities
Assets:
Available-for-sale securities		0		0
Level 1 | Fixed maturities | Mortgage- and asset-backed securities
Assets:
Available-for-sale securities		0		0
Level 1 | Fixed maturities | Public utilities
Assets:
Available-for-sale securities		0		0
Level 1 | Fixed maturities | Sovereign and supranational
Assets:
Available-for-sale securities		0		0
Level 1 | Fixed maturities | Banks/financial institutions
Assets:
Available-for-sale securities		0		0
Level 1 | Fixed maturities | Other corporate
Assets:
Available-for-sale securities		0		0
Level 1 | Equity securities
Assets:
Available-for-sale securities				1,001
Level 2
Assets:
Available-for-sale securities		53,272		53,790
Equity securities		77
Asset derivatives		556		180
Other Investments				0
Cash and cash equivalents		0		0
Total assets		53,905		53,976
Liabilities:
Total liabilities		267		346
Level 2 | Foreign currency swaps
Assets:
Asset derivatives		130		146
Liabilities:
Liability derivatives		179		69
Level 2 | Foreign currency forwards
Assets:
Asset derivatives		426		22
Liabilities:
Liability derivatives		85		274
Level 2 | Foreign currency options
Assets:
Asset derivatives				12
Liabilities:
Liability derivatives		3		3
Level 2 | Credit default swaps
Assets:
Asset derivatives		0		0
Level 2 | Fixed maturities
Assets:
Available-for-sale securities		53,272		53,790
Level 2 | Fixed maturities | Government and agencies
Assets:
Available-for-sale securities		1,411		1,121
Level 2 | Fixed maturities | Municipalities
Assets:
Available-for-sale securities		1,373		1,370
Level 2 | Fixed maturities | Mortgage- and asset-backed securities
Assets:
Available-for-sale securities		269		269
Level 2 | Fixed maturities | Public utilities
Assets:
Available-for-sale securities		7,724		7,886
Level 2 | Fixed maturities | Sovereign and supranational
Assets:
Available-for-sale securities		1,866		1,909
Level 2 | Fixed maturities | Banks/financial institutions
Assets:
Available-for-sale securities		9,120		8,908
Level 2 | Fixed maturities | Other corporate
Assets:
Available-for-sale securities		31,509		32,327
Level 2 | Equity securities
Assets:
Available-for-sale securities				6
Level 3
Assets:
Available-for-sale securities		436		414
Equity securities		16
Asset derivatives		241		151
Other Investments				0
Cash and cash equivalents		0		0
Total assets		693		581
Liabilities:
Total liabilities		86		128
Level 3 | Foreign currency swaps
Assets:
Asset derivatives		240		150
Liabilities:
Liability derivatives		86		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
Liabilities:
Liability derivatives		0		0
Level 3 | Credit default swaps
Assets:
Asset derivatives		1		1
Level 3 | Fixed maturities
Assets:
Available-for-sale securities		436		414
Level 3 | Fixed maturities | Government and agencies
Assets:
Available-for-sale securities		0		0
Level 3 | Fixed maturities | Municipalities
Assets:
Available-for-sale securities		0		0
Level 3 | Fixed maturities | Mortgage- and asset-backed securities
Assets:
Available-for-sale securities		186		175
Level 3 | Fixed maturities | Public utilities
Assets:
Available-for-sale securities		83		68
Level 3 | Fixed maturities | Sovereign and supranational
Assets:
Available-for-sale securities		0		0
Level 3 | Fixed maturities | Banks/financial institutions
Assets:
Available-for-sale securities		24		25
Level 3 | Fixed maturities | Other corporate
Assets:
Available-for-sale securities		$ 143		146
Level 3 | Equity securities
Assets:
Available-for-sale securities				$ 16

[1] Includes perpetual securities

[2] Includes perpetual securities ($1,506 at amortized cost and $1,774 at fair value)

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

[4] Includes perpetual securities ($71 at fair value)