Investments (Details 47) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Real Estate Investment Property at Cost
Traditional, Carrying Value	$ 5,845	$ 4,871
Real estate joint ventures and funds, Carrying Value	2,340	2,707
Real estate and real estate joint ventures, Carrying Value	8,185	7,578
Foreclosed, Carrying Value	264	152
Real estate held-for-investment, Carrying Value	8,449	7,730
Real estate held-for-sale, Carrying Value	114	300
Total real estate and real estate joint ventures, Carrying Value	$ 8,563	$ 8,030
Traditional, % of Total	68.30%	60.70%
Real estate joint ventures and funds, % of Total	27.30%	33.70%
Real estate and real estate joint ventures, % of Total	95.60%	94.40%
Foreclosed, % of Total	3.10%	1.90%
Real estate held-for-investment, % of Total	98.70%	96.30%
Real estate held-for-sale, % of Total	1.30%	3.70%
Total real estate and real estate joint ventures, % of Total	100.00%	100.00%

The subtotal of net real estate and real estate joint ventures.

No definition available.

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The percentageof the Subtotal net real estate and real estate joint ventures.

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No definition available.

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- Definition

The percentage of carrying amount as of the balance sheet date of land and buildings obtained through foreclosure proceedings or defeasance in full or partial satisfaction of a debt arrangement.

+ References

No definition available.

+ Details

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- Definition

The percentage of carrying amount as of the balance sheet date of investments in land and buildings held for sale, excluding real estate considered to be inventory of the entity.

+ References

No definition available.

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- Definition

The percentage of total investments in real estate held solely for investment purposes.

+ References

No definition available.

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Represents a percentage of total which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

+ References

No definition available.

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The percentage of investments in real estate held solely for investment purposes (income production and capital appreciation).

+ References

No definition available.

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- Definition

The percentage of carrying amount of investments in unconsolidated real estate and other joint ventures not separately presented. This includes direct and indirect investments.

+ References

No definition available.

+ Details

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- Definition

Carrying amount as of the balance sheet date of land and buildings obtained through foreclosure proceedings or defeasance in full or partial satisfaction of a debt arrangement.

+ References

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

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-DEP

-Chapter 11

-Paragraph 2, 9, 10, 11

-IssueDate 2006-05-01

-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 Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 45

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6375948&loc=d3e4437-111522

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph c

-Subparagraph Schedule III

-Article 5

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 28

-Article 12

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

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 01-6

-Paragraph 13

-Subparagraph f

-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.

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Carrying amount as of the balance sheet date of investments in land and buildings held for sale, excluding real estate considered to be inventory of the entity.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.1(f))

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Represents a total which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

+ References

Reference 1: 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(d))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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- Definition

The net book value of real estate property held for investment purposes.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

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-Subparagraph (SX 210.7-03.1(d))

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Investments in real estate held solely for investment purposes (income production and capital appreciation).

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 7

-Section 03

-Paragraph 1

-Subparagraph d

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

-Publisher FASB

-Name Accounting Standards Codification

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The carrying amount of investments in unconsolidated real estate and other joint ventures not separately presented. This includes direct and indirect investments.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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-Subparagraph (SX 210.7-03.1(d))

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