Convertible 3.75% Senior Notes (Details Textual) - USD ($)					12 Months Ended
	May 20, 2015	Dec. 31, 2014	Dec. 22, 2014	Dec. 16, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Proceeds from convertible 3.75% senior notes					$ 0	$ 0	$ 138,985,000
Accrued interest					240,000	240,000
Change in the fair value of derivative liability					0	23,144,000	2,300,000
Reclassification of derivative liability to equity	$ 18,300,000				0	18,256,000	0
Deferred financing costs					$ 3,200,000	4,000,000
Convertible debt
Debt Instrument [Line Items]
Face amount of the Notes	$ 143,750,000.00	$ 143,750,000.00		$ 143,750,000.00			$ 143,750,000.00
Stated interest rate	3.75%	3.75%		3.75%	3.75%		3.75%
Conversion price (in dollars per share)	$ 11.29	$ 11.29		$ 11.29	$ 11.29		$ 11.29
Initial conversion rate per $1,000 principal (in shares)	88.572	88.572		88.572	88.5716
Conversion conditions, stock price (greater than)					130.00%
Conversion conditions, trading price (less than)					98.00%
Proceeds from convertible 3.75% senior notes			$ 139,000,000
Payment of debt issuance costs			4,800,000
Accrued interest			200,000
Derivative liability				$ 43,700,000
Effective interest rate				12.94%
Change in the fair value of derivative liability						$ 23,100,000
Reclassification of derivative liability to equity	$ 18,256,000
Remaining discount amortization period					3 years
Initial Issuance | Convertible debt
Debt Instrument [Line Items]
Face amount of the Notes				$ 125,000,000
Additional Principal | Convertible debt
Debt Instrument [Line Items]
Face amount of the Notes			$ 18,750,000.00