INVESTMENTS - Held-to-Maturity Investments in Debt Securities (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	$ 33,350	$ 33,459
Gross Unrealized Gains	6,735	4,278
Gross Unrealized Losses	64	217
Fair Value	40,021	37,520
Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Fair Value	40,021	37,520
Yen-denominated \| Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	33,350	33,459
Gross Unrealized Gains	6,735	4,278
Gross Unrealized Losses	64	217
Fair Value	40,021	37,520
Japan government and agencies \| Yen-denominated \| Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	20,702
Gross Unrealized Gains	5,338	3,387
Gross Unrealized Losses	0	0
Fair Value	26,040	23,391
Municipalities \| Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	350	341
Fair Value	457	415
Municipalities \| Yen-denominated \| Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	350
Gross Unrealized Gains	107	74
Gross Unrealized Losses	0	0
Fair Value	457	415
Mortgage- and asset-backed securities \| Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	30	36
Fair Value	32	38
Mortgage- and asset-backed securities \| Yen-denominated \| Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	30
Gross Unrealized Gains	2	2
Gross Unrealized Losses	0	0
Fair Value	32	38
Public utilities \| Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,201	3,092
Fair Value	3,536	3,203
Public utilities \| Yen-denominated \| Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,201
Gross Unrealized Gains	358	205
Gross Unrealized Losses	23	94
Fair Value	3,536	3,203
Sovereign and supranational \| Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	2,602	2,555
Fair Value	2,877	2,711
Sovereign and supranational \| Yen-denominated \| Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	2,602
Gross Unrealized Gains	283	182
Gross Unrealized Losses	8	26
Fair Value	2,877	2,711
Banks/financial institutions \| Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,731	4,431
Fair Value	3,900	4,546
Banks/financial institutions \| Yen-denominated \| Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,731
Gross Unrealized Gains	195	168
Gross Unrealized Losses	26	53
Fair Value	3,900	4,546
Other corporate \| Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	2,734	3,000
Fair Value	3,179	3,216
Other corporate \| Yen-denominated \| Fixed maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	2,734
Gross Unrealized Gains	452	260
Gross Unrealized Losses	7	44
Fair Value	$ 3,179	$ 3,216

Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27232-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27232-111563

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.6)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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