Credit Facilities (Details) (USD $)	0 Months Ended				0 Months Ended				12 Months Ended	0 Months Ended	9 Months Ended		0 Months Ended							12 Months Ended
	Dec. 10, 2013	Sep. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 03, 2013 Revolving Credit Facility Wells Fargo Bank	Dec. 03, 2013 Revolving Credit Facility Wells Fargo Bank Debt Instrument, Measurement Period One	Dec. 03, 2013 Revolving Credit Facility Wells Fargo Bank Debt Instrument, Measurement Period Two	Dec. 03, 2013 Revolving Credit Facility Wells Fargo Bank Debt Instrument, Measurement Period Three	Dec. 31, 2013 Revolving Credit Facility Wells Fargo Bank Debt Instrument, Measurement Period Three	Dec. 03, 2013 Revolving Credit Facility Wells Fargo Bank Debt Instrument, Measurement Period Four	Sep. 30, 2014 Revolving Credit Facility Wells Fargo Bank Debt Instrument, Measurement Period Five	Dec. 03, 2013 Letter of Credit Wells Fargo Bank	Dec. 10, 2013 Convertible Senior Notes Issued December, 2013 Convertible Debt	Dec. 10, 2013 Debt Instrument, Redemption, Period One Convertible Senior Notes Issued December, 2013 Convertible Debt D	Dec. 10, 2013 Debt Instrument, Redemption, Period Two Convertible Senior Notes Issued December, 2013 Convertible Debt D	Dec. 10, 2013 Other Assets Convertible Senior Notes Issued December, 2013 Convertible Debt	Dec. 10, 2013 Additional Paid-in Capital Convertible Senior Notes Issued December, 2013 Convertible Debt	Dec. 31, 2013 Minimum Convertible Senior Notes Issued December, 2013 Convertible Debt	Dec. 31, 2013 Maximum Convertible Senior Notes Issued December, 2013 Convertible Debt	Dec. 31, 2013 Prime Rate Revolving Credit Facility Wells Fargo Bank
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
Threshold Trading Days														20	20
Threshold Consecutive Trading Days														30 days	30 days
Threshold Percentage of Stock Price Trigger														130.00%	98.00%
Stock Issued During Period, Shares, Conversion of Convertible Securities													41.6051
Redemption Price, Percentage													100.00%	100.00%
Threshold Business Days															5
Threshold Consecutive Business Days															5 years
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			2,900,000	800,000
Convertible notes		69,554,000	67,101,000
Deferred Finance Costs, Noncurrent, Net		2,500,000
Estimated Annual Interest Expense, Debt																		5,700,000	6,900,000
Payments of Derivative Issuance Costs	7,400,000
Debt Instrument, Convertible, Conversion Price													$ 24.04
Derivative, Cap Price													29.02
Aggregate maximum borrowing capacity					20,000,000							7,500,000
Letters of credit outstanding, amount				6,400,000
Debt instrument, basis spread on variable rate																				1.00%
Debt Covenant, Minimum Current Ratio					2.0
Debt Covenant, Maximum Operating Loss						11,000,000	18,000,000	22,000,000		26,000,000
Debt Covenant, Maximum Annual Capital Expenditures									$ 6,000,000		$ 13,000,000