Represents the information about aggregate additional principal amount that may increase.

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Represents the amount of amortization of principal in the fifth year of the credit facility under the credit agreement.

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Represents the amount of amortization of principal in the fourth year of the credit facility under the credit agreement.

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No definition available.

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Represents the amount of amortization of principal in the first year of the credit facility under the credit agreement.

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Represents the amount of amortization of principal in the sixth year of the credit facility under the credit agreement.

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Represents the amount of amortization of principal in the third year of the credit facility under the credit agreement.

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Represents the amount of amortization of principal in the second year of the credit facility under the credit agreement.

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No definition available.

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Represents the total debt to EBITDA ratio that is required to be maintained by the entity under the credit agreement.

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Represents the period after the end of each fiscal year repayment of mandatory periodic principal is required to be made as defined under the credit agreement.

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No definition available.

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Obligations related to long-term debt and capital lease obligations.

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No definition available.

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Represents the obligations related to long-term debt and capital lease obligations, excluding debt discount.

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No definition available.

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Amount of noncash expense included in interest expense to allocate debt discount and premium, and the costs to issue debt and obtain financing over the related debt instruments. Alternate captions include noncash interest expense.

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Amount of the total principal payments made during the annual reporting period.

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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No definition available.

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The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

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Amount of the cost of borrowed funds accounted for as interest expense.

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

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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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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.

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

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Amount of long-term debt and capital lease obligation due after one year or beyond the normal operating cycle, if longer.

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

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Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

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Borrowing Arrangements (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Feb. 20, 2015	Dec. 31, 2014
Borrowing arrangements
Total debt	$ 267,171			$ 253,400
Less current portion	15,943			15,567
Long-term borrowings, excluding current portion	251,228			237,833
Senior Credit Facility
Interest Expense	4,043us-gaap_InterestExpense	4,809us-gaap_InterestExpense
Amortization of debt discount and issuance costs	634	115
Senior Credit Facility, net of discount
Borrowing arrangements
Total debt	264,927			251,010
Senior Credit Facility
Maximum borrowing capacity	450,000
Current borrowing capacity	75,701
Letters of credit outstanding	53,449
Borrowings excluding debt discount	267,100
Less: Discount on debt	2,173
Available borrowing capacity	75,701
Credit facility outstanding			147,299
Period after end of each fiscal year mandatory repayment of principal required to be made	90 days
Repayment of mandatory principal		7,940
Senior Credit Facility, net of discount \| Maximum
Senior Credit Facility
Total debt to EBITDA ratio that is required to be maintained	4.0
Senior Credit Facility, net of discount \| Maximum \| Period End of Each Fiscal Quarter Ending after 1st July 2014 Through 30th June 2015
Senior Credit Facility
Total debt to EBITDA ratio that is required to be maintained	3.75
Senior Credit Facility, net of discount \| Maximum \| End of each fiscal quarter ending after July 1, 2014 through and including June 30, 2016
Senior Credit Facility
Total debt to EBITDA ratio that is required to be maintained	3.5
Senior Credit Facility, net of discount \| Base rate loans \| Base Rate
Senior Credit Facility
Interest rate margin on variable rate basis (as a percent)	0.50%
Senior Credit Facility, net of discount \| Base rate loans \| LIBOR
Senior Credit Facility
Interest rate margin on variable rate basis (as a percent)	1.00%
Revolving credit facility
Senior Credit Facility
Maximum borrowing capacity	200,000		200,000
Aggregate additional principal amount			100,000
Letter of credit facility
Senior Credit Facility
Maximum borrowing capacity	100,000		100,000
Credit facility outstanding			53,449
Swing-Line Loan Facility
Senior Credit Facility
Maximum borrowing capacity			20,000
Term loan facility
Senior Credit Facility
Maximum borrowing capacity			200,000	250,000
Restated Secured Credit Facility
Senior Credit Facility
Maximum borrowing capacity			400,000
Amount borrowed			10,400
Amortization of principal in the first year			15,000
Amortization of principal in the second year			15,000
Amortization of principal in the third year			20,000
Amortization of principal in the fourth year			20,000
Amortization of principal in the fifth year			20,000
Amortization of principal in the sixth year			110,000
Other obligations
Borrowing arrangements
Total debt	$ 2,244			$ 2,390