Debt (Long Term Debt Instruments) (Detail) (USD $)	9 Months Ended
Sep. 30, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Total debt	$ 833,200,000	$ 598,900,000
Less current maturities	(53,343,000)	(52,596,000)
Long-term debt	779,920,000	546,323,000
Senior Notes [Member] \| 4.875% Senior Notes [Member] \| Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Mar. 15, 2023
Carrying value of debt	400,000,000	0
Senior Notes [Member] \| 7.625% Senior Notes [Member] \| Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Feb. 01, 2017
Carrying value of debt	0	150,000,000
Convertible Debt [Member] \| 2011 4.0% Notes [Member] \| Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Jun. 15, 2014
Carrying value of debt	103,100,000	100,900,000
Convertible Debt [Member] \| 2011 4.25% Notes [Member] \| Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Dec. 15, 2014
Carrying value of debt	93,900,000	92,100,000
Convertible Debt [Member] \| 2009 4.0% Notes [Member] \| Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Jun. 15, 2014
Carrying value of debt	9,600,000	9,700,000
Convertible Debt [Member] \| 2009 4.25% Notes [Member] \| Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Dec. 15, 2014
Carrying value of debt	3,000,000	3,000,000
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Capital lease obligations	133,300,000	79,000,000
Capital Lease Obligations [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Lease expiration date	Mar. 31, 2020
Loans Payable [Member]
Debt Instrument [Line Items]
Carrying value of debt	53,900,000	30,200,000
Loans Payable [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	May 31, 2018
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, expiration date	Aug. 22, 2016
Revolving Credit Facility [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Line of credit facility, expiration date	Aug. 22, 2016
Credit facility, amount outstanding	$ 36,400,000	$ 134,000,000

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

+ 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 210.7-03.16)

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

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.13,16)

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

+ Details

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Period Type:	instant

- Details

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Balance Type:	na
Period Type:	duration

- 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

+ Details

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Period Type:	duration

- Definition

Date which lease or group of leases is set to expire, in CCYY-MM-DD format.

+ References

No definition available.

+ Details

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- Definition

Amount borrowed under the credit facility as of the balance sheet date.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ 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))

-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 19, 22

-Article 5

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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 SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 7

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)

-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 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 03

-Paragraph 16

-Article 9

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20, 22

-Article 5

Reference 6: 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

+ Details

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Period Type:	instant

- Definition

Amount of long-term debt and capital lease obligation due after 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 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)

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

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

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 6

-Section H

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- Definition

Amount of long-term debt and capital leases due within one year or the normal operating cycle, if longer.

+ References

+ Details

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