Debt - 2015 Credit Agreement (Details Textual) - USD ($)	6 Months Ended
Jun. 30, 2015	Jun. 30, 2014
Debt Instrument [Line Items]
Cash used for repayment of debt	$ 123,750,000	$ 7,500,000
Deferred financing costs related to convertible notes	5,900,000
Amortization expenses of deferred financing costs included in Interest expense	900,000
2015 Credit Agreement
Debt Instrument [Line Items]
Credit Agreement	350,000,000
Cash used for repayment of debt	120,000,000
Increase (decrease) in available cash	30,000,000
Financing cost	2,700,000
2015 Credit Agreement \| Revolving Loan
Debt Instrument [Line Items]
Credit Agreement	200,000,000
2015 Credit Agreement \| Term Loan
Debt Instrument [Line Items]
Credit Agreement	$ 150,000,000

Amount of noncash expense included in interest expense to issue debt and obtain financing associated with the related debt instruments. Alternate captions include noncash interest expense.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.8)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 8

-Article 9

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Amount of increase (decrease) in cash. Cash is the amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Includes effect from exchange rate changes.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 830

-SubTopic 230

-Section 45

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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

Amount of debt issuance costs (for example, but not limited to, legal, accounting, broker, and regulatory fees).

+ References

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For an unclassified balance sheet, the carrying amount (net of accumulated amortization) as of the balance sheet date of capitalized costs associated with the issuance of debt instruments (for example, legal, accounting, underwriting, printing, and registration costs) that will be charged against earnings over the life of the debt instruments to which such costs pertain.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 3

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-Topic 210

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-Paragraph 1

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- 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.

+ 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))

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The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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