Debt - 2010 Convertible Notes (Details Textual)	6 Months Ended
Jun. 30, 2015 USD ($) Tradingday $ / shares	Jun. 30, 2014 USD ($) $ / shares	Dec. 31, 2014 USD ($)
Debt Instrument [Line Items]
Debt, carrying amount	$ 285,144,000		$ 255,831,000
2010 Convertible Notes
Debt Instrument [Line Items]
Initial conversion rate of common stock	43.1307	42.8889
Convertible Notes, initial conversion of Par Value Convertible Notes to common stock	$ 1,000	$ 1,000
Initial conversion price \| $ / shares	$ 23.19	$ 23.32
Debt instrument, convertible, terms of conversion feature	Prior to September 1, 2016, holders of the 2010 Convertible Notes can convert their securities at any time in the fiscal quarter following the period in which the price of our common stock trades over 130% of the conversion price for at least 20 consecutive trading days in the last 30 trading days of a fiscal quarter.
Rate of conversion price	130.00%
Debt instrument, convertible, threshold consecutive trading days	20 days
Debt instrument, convertible, threshold trading days \| Tradingday	30
Conversion obligation settlement in cash	100.00%
Stock price \| $ / shares	$ 31.66
Debt instrument convertible, settlement value	$ 205,000,000
Debt, carrying amount	$ 138,900,000

The value of the financial instrument(s) that the original debt is being converted into in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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-Publisher FASB

-Name Accounting Standards Codification

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Dividend or interest rate associated with the financial instrument issued in exchange for the original debt being converted in a noncash or part noncash transaction. Noncash are transactions that affect recognized assets or liabilities but that do not result in cash receipts or cash payments. Part noncash refers to that portion of the transaction not resulting in cash receipts or cash payments.

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The amount of the original debt being converted in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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The price per share of the conversion feature embedded in the debt instrument.

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- Definition

Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

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Description of the conversion terms of a debt instrument which may include the conversion ratio (including all potential conversion ratios if contingently adjustable), type of debt or equity security into which the debt is convertible, the dollars of debt or the number of shares into which the instrument is convertible (or potentially convertible into), the conversion period, any contingencies associated with the conversion terms, and the existence and amount of a beneficial conversion feature.

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Threshold period of specified consecutive trading days within which common stock price to conversion price of convertible debt instruments must exceed threshold percentage for a specified number of trading days to trigger conversion feature, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Threshold number of specified trading days that common stock price to conversion price of convertible debt instruments must exceed threshold percentage within a specified consecutive trading period to trigger conversion feature.

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- Definition

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

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

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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.

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Price of a single share of a number of saleable stocks of a company.

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