Applicable Margin Rate

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Balance Type:	na
Period Type:	instant

- Definition

Debt Disclosure [Line Items]

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- Definition

Debt Instrument, Acceptance Terms

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- Definition

Debt Instrument, Interest Rate, Payment Date

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- Definition

Debt Instrument Offer Price Percentage

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- Definition

Debt Instrument, Prepayment Terms

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- Definition

Debt Redemption Price Percent Of Principal Amount

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Period Type:	instant

- Definition

Debt To Capitalization Ratio

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Balance Type:	na
Period Type:	instant

- Definition

Interest Coverage ratio

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Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Line of Credit Facility, Additional Borrowing Capacity

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Balance Type:	credit
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Number of Covenants

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- Definition

Percentage of repurchase price to principal debt amount

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Balance Type:	na
Period Type:	instant

- Definition

Principal payments, percentage

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- Definition

The component of interest expense comprised of the periodic charge against earnings over the life of the financing arrangement to which such costs relate. Alternate captions include Noncash Interest Expense.

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-SubTopic 10

-Section 45

-Paragraph 28

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Description of minimum financial levels (for example, tangible net worth and working capital) and achievement of certain financial ratios (for example, working capital ratio and debt service coverage ratio), and adherence to certain clauses which generally require or restrict certain actions (for example, entering into a debt arrangement with equal or greater seniority, and selling or discontinuing a certain business segment or material subsidiary) to be in compliance with the covenant clauses of the debt agreement. May also include a discussion of the adverse consequences that would result if the entity violates or fails to satisfy the covenants.

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-Publisher FASB

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-Paragraph 2, 4

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-SubTopic 470

-Section 50

-Paragraph 3

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

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Date that the debt agreement requires the first payment to be made, which may be presented in a variety of ways (year, month and year, day, month and year, quarter, etc.).

+ References

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

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-Name Accounting Standards Codification

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-Subparagraph (SX 210.5-02.22)

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-SubTopic 470

-Section 50

-Paragraph 3

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

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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.

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-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

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-Paragraph 16, 20

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-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 30

-Section 45

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-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

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

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Balance Type:	credit
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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

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-Topic 825

-SubTopic 10

-Section 50

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13476-108611

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- Definition

Interest rate stated in the contractual debt agreement.

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Date when the debt instrument was issued, which may be presented in a variety of ways (year, month and year, day, month and year, quarter, etc.).

+ References

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Date when the debt instrument is scheduled to be fully repaid, which may be presented in a variety of ways (year, month and year, day, month and year, quarter, etc.).

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(2))

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

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- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

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-Name Accounting Standards Codification

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-Section S99

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-Subparagraph (SX 210.9-03.16)

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-Name Accounting Standards Codification

-Topic 944

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-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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Balance Type:	credit
Period Type:	instant

- Definition

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

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Description of the conditions for borrowing under the credit facility including the nature of any restrictions.

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

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-Publisher SEC

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-Number 210

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-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

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- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

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-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

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Balance Type:	credit
Period Type:	instant

- Definition

Description of the frequency of the required periodic payments of interest, principal, or both, and the amount, if set, or a description of a formula upon which payment is based.

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

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-Publisher SEC

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-Number 210

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-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

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Description of the frequency of periodic payments, which may be presented in a variety of ways (for example, monthly, quarterly, annually).

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

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-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

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- Definition

Reflects when the credit facility first became available, which may be presented in a variety of ways (year, month and year, day, month and year, quarter).

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

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-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

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Data Type:	us-types:dateStringItemType
Balance Type:	na
Period Type:	duration

- Definition

The effective interest rate at the end of the reporting period.

+ References

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

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-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

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ Details

Name:	us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	us-gaap
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt.

+ References

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

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 95-13

-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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-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3291-108585

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Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow to pay off an obligation from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with either short term or long term maturity.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (b)

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 18

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

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Period Type:	duration

Long Term Debt - Additional Information (Detail) (USD $)	1 Months Ended		3 Months Ended	9 Months Ended		1 Months Ended			1 Months Ended			1 Months Ended	9 Months Ended	1 Months Ended					1 Months Ended		1 Months Ended					1 Months Ended		1 Months Ended		1 Months Ended
	Oct. 31, 2010	Oct. 05, 2010	Sep. 30, 2011	Sep. 30, 2011	Sep. 30, 2010	Aug. 19, 2010 Minimum 2010 Credit Agreement Point	Aug. 19, 2010 Minimum 2010 Credit Agreement LIBOR	Aug. 19, 2010 Minimum 2010 Credit Agreement Base Rate	Aug. 19, 2010 Maximum 2010 Credit Agreement	Aug. 19, 2010 Maximum 2010 Credit Agreement LIBOR	Aug. 19, 2010 Maximum 2010 Credit Agreement Base Rate	Aug. 19, 2010 2010 Credit Agreement LegalMatter	Sep. 30, 2011 2010 Credit Agreement	Aug. 19, 2010 2010 Credit Agreement Revolving Credit Facility	Sep. 30, 2011 2010 Credit Agreement Revolving Credit Facility	Sep. 30, 2011 2010 Credit Agreement Revolving Credit Facility Letter of Credit	Aug. 19, 2010 2010 Credit Agreement Revolving Credit Facility Letter of Credit	Aug. 19, 2010 2010 Credit Agreement Revolving Credit Facility Swing Line Facility	Aug. 19, 2010 2010 Credit Agreement Term Loan Facility	Sep. 30, 2011 2010 Credit Agreement Term Loan Facility	Aug. 19, 2010 2010 Credit Agreement Term Loan Facility First Four Quarterly Installments	Aug. 19, 2010 2010 Credit Agreement Term Loan Facility Subsequent Eight Quarterly Installments	Aug. 19, 2010 2010 Credit Agreement Term Loan Facility Next Subsequent Three Quarterly Installments	Sep. 30, 2011 2010 Credit Agreement LIBOR	Sep. 30, 2011 2010 Credit Agreement Base Rate	Oct. 05, 2010 Minimum Series A, Senior Notes, 4.97 Percent, Due October 5th 2020 Point	Oct. 05, 2010 Maximum Series A, Senior Notes, 4.97 Percent, Due October 5th 2020	Oct. 05, 2010 Series A, Senior Notes, 4.97 Percent, Due October 5th 2020 LegalMatter	Sep. 30, 2011 Series A, Senior Notes, 4.97 Percent, Due October 5th 2020	Oct. 05, 2010 Series A, Senior Notes, 4.97 Percent, Due October 5th 2020 Semi Annual Payment, First Payment	Oct. 05, 2010 Series A, Senior Notes, 4.97 Percent, Due October 5th 2020 Semi Annual Payment, Second Payment
Debt Disclosure [Line Items]
Credit agreement date												2010-08-19
Current aggregate borrowing capacity														$ 400,000,000			$ 150,000,000	$ 40,000,000
Notes isuance date																												2010-10-05
Aggregate amount by which the revolving credit facility can be increased														100,000,000
Long-term debt, aggregate principal amount																												300,000,000
Debt interest rate																												4.97%
Debt maturity date														Aug. 19, 2013					Aug. 19, 2014									Oct. 05, 2020
Credit facility, maximum borrowing capacity														500,000,000
Line of credit																			100,000,000
Line of credit facility, frequency of payment and payment terms																			The term loan facility is payable in quarterly principal installments commencing November 19, 2010. The installment amounts vary from 1.25% of the original principal amount for each of the first four quarterly installments, 2.50% of the original principal amount for each of the subsequent eight quarterly installments, 5.00% of the original principal amount for the next subsequent three quarterly installments, with the remainder becoming due at maturity.
Line of credit facility, frequency of payments																			Quarterly
Commencement date of interest payments																			2010-11-19
Installment amounts percentage of the original principal amount																					1.25%	2.50%	5.00%			5.00%
Applicable margin							2.75%	1.75%		3.75%	2.75%													2.75%	1.75%
Commitment fee payable to the lenders for the unused portion of the revolving credit facility						0.50%			0.75%				0.50%
Financial covenant description																												The Company must not permit its debt to capitalization ratio to exceed 50% at any time. The note purchase agreement generally defines the debt to capitalization ratio as the ratio of (a) total borrowed money indebtedness to (b) the sum of such indebtedness plus consolidated net worth, with consolidated net worth determined as of the last day of the most recently ended fiscal quarter. The Company also must not permit the interest coverage ratio as of the last day of a fiscal quarter to be less than 2.50 to 1.00. The note purchase agreement generally defines the interest coverage ratio as the ratio for the four prior quarters of EBITDA to interest charges for that same period.
Financial covenant description												The Company must not permit its debt to capitalization ratio to exceed 45% at any time. The 2010 Credit Agreement generally defines the debt to capitalization ratio as the ratio of (a) total borrowed money indebtedness to (b) the sum of such indebtedness plus consolidated net worth, with consolidated net worth determined as of the last day of the most recently ended fiscal quarter. The Company also must not permit the interest coverage ratio as of the last day of a fiscal quarter to be less than 3.00 to 1.00. The 2010 Credit Agreement generally defines the interest coverage ratio as the ratio of earnings before interest, taxes, depreciation and amortization ("EBITDA") of the four prior fiscal quarters to interest charges for the same period.
Number of compliance covenants												2																2
Debt to capitalization ratio, percentage the Company must not exceed at any time									45.00%																		50.00%
Interest coverage ratio that the Company must exceed on the last day of the fiscal quarter						3.00																				2.50
Line of credit, amount outstanding															15,800,000					95,000,000
Line of credit, interest rate															5.00%					3.125%
Unfunded letters of credit, amount outstanding			40,600,000	40,600,000												40,600,000
Line of credit, available borrowing capacity															344,000,000
Repayment of revolving credit facility		200,000,000
Long-term debt, fair value																													321,000,000
Debt price as a percentage of principal amount																												100.00%
Description of the prepayment terms																												The Notes are prepayable at the Company's option, in whole or in part, provided that in the case of a partial prepayment, prepayment must be in an amount not less than 5% of the aggregate principal amount of the Notes then outstanding, at any time and from time to time at 100% of the principal amount prepaid, plus accrued and unpaid interest to the prepayment date
Prepayment terms, percent of principal before accrued and unpaid interest and "make-whole" premium																												100.00%
Description of the acceptance terms																												If any offer to prepay is accepted, the purchase price of each prepaid Note is 100% of the principal amount thereof, plus accrued and unpaid interest thereon to the prepayment date.
Acceptance terms, percent of principal before accrued and unpaid interest																												100.00%
Interest pay date																														April 5	October 5
Debt issuance costs	10,800,000				10,328,000
Interest expense related to amortization of debt issuance costs			$ 604,000	$ 1,800,000