Fair Value (Carrying amount and estimated fair value of financial instrument assets and liabilities which are not measured at fair value) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Financial Assets [Abstract]
Notes receivable for the issuance of common stock	$ 1	$ 1
Mortgage loans	586	588
Financial Liabilities [Abstract]
Long term debt	2,560us-gaap_LongTermDebtNoncurrent	2,559us-gaap_LongTermDebtNoncurrent
Carrying Amount [Member]
Financial Assets [Abstract]
Notes receivable for the issuance of common stock	1	1
Mortgage loans	586	588
Financial Liabilities [Abstract]
Long term debt	2,560	2,559
Estimated Fair Value [Member]
Financial Assets [Abstract]
Notes receivable for the issuance of common stock	1	1
Mortgage loans	612	608
Financial Liabilities [Abstract]
Long term debt	2,908	2,883
Level 1 [Member] \| Estimated Fair Value [Member]
Financial Assets [Abstract]
Notes receivable for the issuance of common stock	0	0
Mortgage loans	0	0
Financial Liabilities [Abstract]
Long term debt	0	0
Level 2 [Member] \| Estimated Fair Value [Member]
Financial Assets [Abstract]
Notes receivable for the issuance of common stock	0	0
Mortgage loans	0	0
Financial Liabilities [Abstract]
Long term debt	2,908	2,883
Level 3 [Member] \| Estimated Fair Value [Member]
Financial Assets [Abstract]
Notes receivable for the issuance of common stock	1	1
Mortgage loans	612	608
Financial Liabilities [Abstract]
Long term debt	$ 0	$ 0

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- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, excluding amounts to be repaid within one year or the normal operating cycle, if longer (current maturities). Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

+ Details

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- Definition

The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio.

+ 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(c))

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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Subparagraph c

-Article 7

+ Details

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- Definition

Amounts receivable from officers and directors resulting from the sale of stock to officers or directors before the cash payment is received.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 30

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.29,30)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SAB TOPIC 4.E)

-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74512-122707

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

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 4

-Section E

+ Details

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