INVESTMENTS - Held-to-Maturity Investments in Debt Securities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	$ 34,242us-gaap_HeldToMaturitySecurities	$ 44,415us-gaap_HeldToMaturitySecurities
Gross Unrealized Gains	4,379	2,041
Gross Unrealized Losses	124	610
Fair Value	38,497	45,846
Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	34,242	44,415
Fair Value	38,497	45,846
Yen-denominated \| Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	34,242
Gross Unrealized Gains	4,379	2,041
Gross Unrealized Losses	124	610
Fair Value	38,497	45,846
Japan government and agencies \| Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	20,023	27,362
Fair Value	23,218	28,708
Japan government and agencies \| Yen-denominated \| Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	20,023
Gross Unrealized Gains	3,195	1,347
Gross Unrealized Losses	0	1
Fair Value	23,218	28,708
Municipalities \| Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	346	399
Fair Value	417	440
Municipalities \| Yen-denominated \| Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	346
Gross Unrealized Gains	71	41
Gross Unrealized Losses	0	0
Fair Value	417	440
Mortgage- and asset-backed securities \| Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	43	58
Fair Value	46	61
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	43
Gross Unrealized Gains	3	3
Gross Unrealized Losses	0	0
Fair Value	46	61
Public utilities \| Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,342	3,900
Fair Value	3,603	3,928
Public utilities \| Yen-denominated \| Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,342
Gross Unrealized Gains	281	150
Gross Unrealized Losses	20	122
Fair Value	3,603	3,928
Sovereign and supranational \| Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	2,556	2,941
Fair Value	2,814	3,040
Sovereign and supranational \| Yen-denominated \| Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	2,556
Gross Unrealized Gains	272	171
Gross Unrealized Losses	14	72
Fair Value	2,814	3,040
Banks/financial Institutions \| Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	4,932	6,310
Fair Value	5,085	6,128
Banks/financial Institutions \| Yen-denominated \| Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	4,932
Gross Unrealized Gains	231	146
Gross Unrealized Losses	78	328
Fair Value	5,085	6,128
Other corporate \| Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,000	3,445
Fair Value	3,314	3,541
Other corporate \| Yen-denominated \| Fixed Maturities
Schedule of Held-to-maturity Securities [Line Items]
Securities held to maturity, fixed maturities, amortized cost	3,000
Gross Unrealized Gains	326	183
Gross Unrealized Losses	12	87
Fair Value	$ 3,314	$ 3,541

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 (f)

-URI http://asc.fasb.org/extlink&oid=27724398&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=28360136&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 (a)

-URI http://asc.fasb.org/extlink&oid=27724398&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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