Fair Value Measurements - Fair Value of Other Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair value disclosures
Current maturities	$ (20,000)	$ 0
Long-term debt, excluding current maturities	2,017,000	1,752,000
Carrying amount
Fair value disclosures
Debt	2,037,000	1,752,000
Current maturities	(20,000)	0
Long-term debt, excluding current maturities	2,017,000	1,752,000
Estimated fair value
Fair value disclosures
Debt	2,007,444	1,850,867
Current maturities	(20,775)	0
Long-term debt, excluding current maturities	$ 1,986,669	$ 1,850,867

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. 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 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

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-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

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-Publisher FASB

-Name Accounting Standards Codification

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-Section S99

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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20, 22

-Article 5

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Amount of long-term debt, after unamortized discount or premium, scheduled to be repaid within one year or the normal operating cycle, if longer. 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

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