Convertible Subordinated Notes Convertible Subordinated Notes (Narrative) (Details) (Details) $ / shares in Units, $ in Thousands			3 Months Ended
Mar. 31, 2017 USD ($) $ / shares	Mar. 19, 2014 $ / shares	Mar. 31, 2017 USD ($) $ / shares	Mar. 31, 2016 USD ($)
Debt Instrument [Line Items]
Amortization of Debt Issuance Costs			$ 203	$ 221
Convertible Subordinated Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Conversion Ratio	44.4530	44.3169
Long-term Debt, Fair Value	$ 187,400		187,400
Interest Expense, Debt			1,000
Amortization of Debt Issuance Costs			100
Accretion of discount, convertible subordinated notes			$ 1,000	$ 900
Debt instrument, convertible, conversion price (in dollars per share) \| $ / shares	$ 22.50	$ 22.56	$ 22.50
Effective interest rate percentage	2.75%		2.75%	6.75%

Amount of amortization expense attributable to debt issuance costs.

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

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

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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

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The fair value amount of long-term debt 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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Amount of accretion of discount for the standardized measure of discounted future net cash flow related to proved oil and gas reserves.

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