Credit Facilities (Details) (USD $)	0 Months Ended		12 Months Ended	3 Months Ended	12 Months Ended
	Dec. 10, 2013	Dec. 03, 2013	Dec. 31, 2013	Mar. 31, 2015	Dec. 31, 2014
Line of Credit Facility [Line Items]
Convertible notes				$ 71,270,000	$ 70,407,000
Deferred Finance Costs, Noncurrent, Net				2,300,000
Payments of Derivative Issuance Costs	7,400,000
Revolving Credit Facility | Wells Fargo Bank
Line of Credit Facility [Line Items]
Aggregate maximum borrowing capacity		20,000,000
Debt Covenant, Minimum Current Ratio		2.0
Revolving Credit Facility | Wells Fargo Bank | Debt Instrument, Measurement Period One
Line of Credit Facility [Line Items]
Debt Covenant, Maximum Operating Loss		13,500,000
Revolving Credit Facility | Wells Fargo Bank | Debt Instrument, Measurement Period Two
Line of Credit Facility [Line Items]
Debt Covenant, Maximum Operating Loss		23,000,000
Revolving Credit Facility | Wells Fargo Bank | Debt Instrument, Measurement Period Three
Line of Credit Facility [Line Items]
Debt Covenant, Maximum Operating Loss		35,000,000
Debt Covenant, Maximum Annual Capital Expenditures			6,000,000
Revolving Credit Facility | Wells Fargo Bank | Debt Instrument, Measurement Period Four
Line of Credit Facility [Line Items]
Debt Covenant, Maximum Annual Capital Expenditures				3,000,000
Letter of Credit | Wells Fargo Bank
Line of Credit Facility [Line Items]
Aggregate maximum borrowing capacity		7,500,000.0
Convertible Senior Notes Issued December, 2013 | Convertible Debt
Line of Credit Facility [Line Items]
Debt Instrument, Face Amount	86,300,000
Stated interest rate	2.25%
Proceeds from Convertible Debt	82,600,000
Stock Issued During Period, Shares, Conversion of Convertible Securities	41.6051
Redemption Price, Percentage	100.00%
Debt Default, Violation Or Event Of Default, Declaration By Note Holders, Percentage	25.00%
Fair Value Disclosure	66,900,000
Beneficial Conversion Feature	19,300,000
Unamortized Discount	3,700,000
Debt Instrument, Convertible, Conversion Price	$ 24.04
Derivative, Cap Price	29.02
Debt Instrument, Redemption, Period One | Convertible Senior Notes Issued December, 2013 | Convertible Debt
Line of Credit Facility [Line Items]
Threshold Trading Days	20
Threshold Consecutive Trading Days	30 days
Threshold Percentage of Stock Price Trigger	130.00%
Redemption Price, Percentage	100.00%
Debt Instrument, Redemption, Period Two | Convertible Senior Notes Issued December, 2013 | Convertible Debt
Line of Credit Facility [Line Items]
Threshold Trading Days	20
Threshold Consecutive Trading Days	30 days
Threshold Percentage of Stock Price Trigger	98.00%
Threshold Business Days	5
Threshold Consecutive Business Days	5 years
Other Assets | Convertible Senior Notes Issued December, 2013 | Convertible Debt
Line of Credit Facility [Line Items]
Unamortized Discount	2,900,000
Additional Paid-in Capital | Convertible Senior Notes Issued December, 2013 | Convertible Debt
Line of Credit Facility [Line Items]
Unamortized Discount	800,000
Minimum | Convertible Senior Notes Issued December, 2013 | Convertible Debt
Line of Credit Facility [Line Items]
Debt Instrument, Periodic Payment, Interest					5,700,000
Maximum | Convertible Senior Notes Issued December, 2013 | Convertible Debt
Line of Credit Facility [Line Items]
Debt Instrument, Periodic Payment, Interest					$ 6,900,000