v2.4.0.8

Debt Obligations (Changes in Debt Obligations Additional Information) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended						1 Months Ended		9 Months Ended
	Mar. 31, 2008 2.50% convertible senior notes due August 15, 2013 [Member]	Sep. 30, 2013 2.50% convertible senior notes due August 15, 2013 [Member]	Sep. 30, 2013 4.00% senior unsecured notes due January 15, 2015 [Member]	Sep. 30, 2013 5.55% senior unsecured notes due January 15, 2020 [Member]	Sep. 30, 2013 5.25% senior unsecured notes due January 16, 2018 [Member]	Sep. 30, 2013 $450 million senior unsecured term loan facility credit agreement due September 19, 2016 [Member]	Sep. 30, 2013 $750 million revolving credit commitment due September 19, 2016 [Member]	Sep. 30, 2011 2011 Credit Facility [Member]	Sep. 30, 2013 2011 Credit Facility [Member]	Sep. 30, 2013 3.875% senior unsecured notes due June 7, 2021 [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	2.50%	2.50%	4.00%	5.55%	5.25%					3.875%
Debt instrument, maturity date	Aug. 15, 2013	Aug. 15, 2013	Jan. 15, 2015	Jan. 15, 2020	Jan. 16, 2018	Sep. 19, 2016	Sep. 19, 2016	Sep. 19, 2016		Jun. 07, 2021
Debt instrument, principal outstanding	$ 475.0					$ 450.0
Debt Instrument, interest rate during period						1.57%	1.37%
Credit facility, borrowing capacity							$ 750	$ 1,200	$ 1,200

X

- Definition

Amount of long-term debt before deduction of unamortized discount or premium. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, with initial maturities beyond one year or 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 02

-Paragraph 20

-Article 5



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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5



Reference 3: 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 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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-Paragraph 16

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X

- Definition

The average effective interest rate during the reporting period.

+ 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 SEC

-Name Regulation S-X (SX)

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

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-Topic 210

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X

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

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-Article 5



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

-Publisher FASB

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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

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X

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ 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 210.5-02.19(b),22(b))

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