Debt (Long Term Debt Instruments) (Detail) (USD $)	3 Months Ended
Mar. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Total debt	$ 734,700,000	$ 598,900,000
Less current maturities	(49,284,000)	(52,596,000)
Long-term debt	685,390,000	546,323,000
Line of Credit [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, expiration date	Aug. 22, 2016
Credit facility, amount outstanding	0	134,000,000
Convertible Debt [Member] \| New 4.0% Notes [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Jun. 15, 2014
Carrying value of debt	101,600,000	100,900,000
Convertible Debt [Member] \| New 4.25% Notes [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Dec. 15, 2014
Carrying value of debt	92,700,000	92,100,000
Convertible Debt [Member] \| Original 4.0% Notes [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] \| Original 4.25% Notes [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]
Lease expiration date	Jan. 31, 2020
Capital lease obligations	94,300,000	79,000,000
Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Jun. 30, 2018
Carrying value of debt	33,400,000	30,200,000
Unsecured Debt [Member] \| Senior Notes [Member] \| 4.875% Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Mar. 15, 2023
Carrying value of debt	400,000,000	0
Unsecured Debt [Member] \| Senior Notes [Member] \| 7.625% Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	Feb. 01, 2017
Carrying value of debt	$ 0	$ 150,000,000

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.

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 840

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (b)

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- 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

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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

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

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

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-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.

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- Definition

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

+ References

No definition available.

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- Definition

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

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-Name Regulation S-X (SX)

-Number 210

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- Definition

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

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

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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.

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- Definition

Sum of the carrying values as of the balance sheet date of all long-term debt, which is debt initially having maturities due after one year from the balance sheet date or beyond the operating cycle, if longer, but excluding the portions thereof scheduled to be repaid within one year or the normal operating cycle, if longer plus capital lease obligations due to be paid more than one year after the balance sheet date.

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Obligation related to long-term debt (excluding convertible debt) and capital leases, the portion which is due in one year or less in the future.

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