Represents the weighted average interest rate on unsecured debt during the period.

No definition available.

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- Definition

The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 21

-Paragraph 16, 20

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

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- Definition

Interest rate stated in the contractual debt agreement.

+ References

+ Details

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- Definition

When presenting a range of interest rates, the highest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date.

+ References

+ Details

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- Definition

When presenting a range of interest rates, the lowest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date.

+ References

+ Details

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- Details

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-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 210.5-02.22(a)(2))

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

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-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

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Period Type:	duration

- Definition

Latest date the outstanding debt instruments are required to be repaid, in CCYY-MM-DD format.

+ References

+ Details

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Period Type:	duration

- Definition

Earliest date the outstanding debt instruments are required to be repaid, in CCYY-MM-DD format.

+ References

+ Details

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- Details

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- Definition

Including the current and noncurrent portions, aggregate carrying amount of all types of notes payable, as of the balance sheet date, with initial maturities beyond one year or beyond the normal operating cycle, if longer.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 13, 16

-Article 9

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

+ Details

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- Definition

Aggregate notional amount of interest rate derivatives, which relates to the currency amount specified in the interest rate derivative instruments.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5579245-113959

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Notional Amount

-URI http://asc.fasb.org/extlink&oid=6519104

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1B

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5580258-113959

+ Details

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Debt Notes (Details) (USD $)	12 Months Ended
Debt Notes (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Aug. 23, 2006
Debt Instrument [Line Items]
Notional Amount of Interest Rate Derivatives	$ 300,000,000
Debt Instrument, Face Amount		1,000,000,000	600,000,000
Debt Instrument, Interest Rate, Stated Percentage				3.85%
Summary of Company's unsecured note balances and certain interest rate and maturity date information
Notes, net	4,630,875,000	5,609,574,000
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum	0.11%	0.05%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum	11.25%	11.25%
Five Point Two Zero Percentage Fixed Rate Tax Exempt Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	400,000,000
Debt Instrument, Interest Rate, Stated Percentage	5.20%
Debt Instrument, Maturity Date	Apr. 01, 2013
Fixed Rate Public or Private Notes [Member]
Summary of Company's unsecured note balances and certain interest rate and maturity date information
Notes, net	4,329,352,000	4,803,191,000
Weighted Average Interest Rate	5.70%	5.84%
Floating Rate Public or Private Notes [Member]
Summary of Company's unsecured note balances and certain interest rate and maturity date information
Notes, net	$ 301,523,000	$ 806,383,000
Weighted Average Interest Rate	1.83%	1.67%
Floating Rate Public or Private Notes [Member]
Summary of Company's unsecured note balances and certain interest rate and maturity date information
Debt Instrument, Maturity Date Range, Start	Jan. 01, 2013	Jan. 01, 2012
Debt Instrument, Maturity Date Range, End	Jan. 01, 2013	Jan. 01, 2013
Fixed Rate Public or Private Notes [Member]
Summary of Company's unsecured note balances and certain interest rate and maturity date information
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum	4.625%	4.625%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum	7.57%	7.57%
Debt Instrument, Maturity Date Range, Start	Jan. 01, 2013	Jan. 01, 2012
Debt Instrument, Maturity Date Range, End	Jan. 01, 2026	Jan. 01, 2026