Convertible 3.75% Senior Notes (Details Textual) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended		12 Months Ended
	May. 20, 2015	Dec. 22, 2014	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 16, 2014
Debt Instrument [Line Items]
Payments of Debt Issuance Costs			$ 0	$ 9
Deferred Tax Liabilities, Deferred Expense, Deferred Financing Costs			3,800	4,600
Unrealized Gain (Loss) on Derivatives			0	8,625
Qualified Institutional Buyers [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 18,750					$ 125,000
Convertible Notes Payable [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 143,750					$ 143,750	143,750
Proceeds from Issuance of Senior Long-term Debt		139,000
Payments of Debt Issuance Costs		$ 4,800
Interest Payable			$ 1,600
Debt Instrument, Convertible, Terms of Conversion Feature			The Notes are convertible at an initial conversion price of approximately $11.29 per share, which is equivalent to an initial conversion rate of 88.5716 shares per $1,000 principal amount of Notes, subject to adjustment in certain events, such as distributions of dividends or stock splits. Holders may convert their Notes at their option prior to September 15, 2019, when or if certain conditions have been met or circumstances have occurred, such as if the Company’s stock price exceeds 130% of the conversion price under the Notes for a designated period of time, or if the trading price of the Notes is, for a designated period of time, less than 98% of the closing sale price of the Company’s common stock multiplied by the then-current conversion rate of the Notes, or if  the Company calls Notes for redemption, or if certain specified corporate events occur. Holders may also convert their Notes at their option at any time on or after September 15, 2019 and prior to the close of business on the business day immediately preceding the stated maturity date. In addition, following the occurrence of certain changes of control of the Company described in the Indenture governing the Notes or termination of trading of the Company’s common stock or other securities into which the Notes are convertible (a “make-whole fundamental change”) or the delivery by the Company of a notice of redemption, the conversion rate for a holder who elects to convert its Notes in connection with such make-whole fundamental change or such notice of redemption will increase in certain circumstances. Additionally, subject to certain conditions, the Company may redeem for cash any or all outstanding Notes on or after December 19, 2017 in an amount equal to the outstanding principal amount of such Notes, plus accrued and unpaid interest.
Derivative Liability				$ 8,600			$ 43,700
Debt Instrument, Interest Rate, Effective Percentage							12.94%
Debt Instrument, Interest Rate, Stated Percentage	3.75%					3.75%	3.75%
Embedded Derivative, No Longer Bifurcated, Amount Reclassified to Stockholders' Equity	$ 18,300
Unrealized Gain (Loss) on Derivatives					$ 23,100
Debt Instrument, Convertible, Remaining Discount Amortization Period			3 years 9 months