Carrying Values and Estimated Fair Values of Financial Instruments (Detail) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Assets:
Equity securities	$ 24	$ 23
Investments other than Consolidated Variable Interest Entities \| Carrying Value
Assets:
Fixed-maturity securities	86,209	72,570
Perpetual securities	5,215	5,974
Variable Interest Entity, Consolidated \| Carrying Value
Assets:
Fixed-maturity securities	6,017	5,869
Perpetual securities	1,315	1,538
Carrying Value
Assets:
Equity securities	24	23
Interest rate, foreign currency, and credit default swaps	407	564
Liabilities:
Notes payable (excluding capitalized leases)	3,293	3,032
Interest rate, foreign currency, and credit default swaps	608	741
Obligation to Japanese policyholder protection corporation	72	108
Investments other than Consolidated Variable Interest Entities \| Fair Value
Assets:
Fixed-maturity securities	85,087	72,999
Perpetual securities	5,215	5,974
Variable Interest Entity, Consolidated \| Fair Value
Assets:
Fixed-maturity securities	5,899	5,825
Perpetual securities	1,315	1,538
Fair Value
Assets:
Equity securities	24	23
Interest rate, foreign currency, and credit default swaps	407	564
Liabilities:
Notes payable (excluding capitalized leases)	3,423	3,248
Interest rate, foreign currency, and credit default swaps	608	741
Obligation to Japanese policyholder protection corporation	72	108
Investments other than Consolidated Variable Interest Entities
Assets:
Perpetual securities	5,215	5,974
Variable Interest Entity, Consolidated
Assets:
Interest rate, foreign currency, and credit default swaps	407	564
Perpetual securities	$ 1,315	$ 1,538

For an unclassified balance sheet, this item represents equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 3

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 19

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 320

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6379932&loc=d3e22054-111558

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 16

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 22

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 86-40

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

- Definition

Fair values as of the balance sheet date of all assets resulting from contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements.

+ References+ Details