Credit Facilities (Details) (USD $)	0 Months Ended			0 Months Ended		0 Months Ended							12 Months Ended	0 Months Ended			12 Months Ended	0 Months Ended	6 Months Ended
	Dec. 10, 2013	Jun. 30, 2014	Dec. 31, 2013	Dec. 03, 2013 Revolving Credit Facility Wells Fargo Bank [Member]	Dec. 03, 2013 Letter of Credit [Member] Wells Fargo Bank [Member]	Dec. 10, 2013 Convertible Senior Notes Issued December, 2013 [Member] Convertible Debt [Member]	Dec. 10, 2013 Debt Instrument, Redemption, Period One [Member] Convertible Senior Notes Issued December, 2013 [Member] Convertible Debt [Member] D	Dec. 10, 2013 Debt Instrument, Redemption, Period Two [Member] Convertible Senior Notes Issued December, 2013 [Member] Convertible Debt [Member] D	Dec. 10, 2013 Other Assets [Member] Convertible Senior Notes Issued December, 2013 [Member] Convertible Debt [Member]	Dec. 10, 2013 Additional Paid-in Capital [Member] Convertible Senior Notes Issued December, 2013 [Member] Convertible Debt [Member]	Dec. 31, 2013 Minimum Convertible Senior Notes Issued December, 2013 [Member] Convertible Debt [Member]	Dec. 31, 2013 Maximum Convertible Senior Notes Issued December, 2013 [Member] Convertible Debt [Member]	Dec. 31, 2013 Prime Rate [Member] Revolving Credit Facility Wells Fargo Bank [Member]	Dec. 03, 2013 Debt Instrument, Measurement Period One [Member] Revolving Credit Facility Wells Fargo Bank [Member]	Dec. 03, 2013 Debt Instrument, Measurement Period Two [Member] Revolving Credit Facility Wells Fargo Bank [Member]	Dec. 03, 2013 Debt Instrument, Measurement Period Three [Member] Revolving Credit Facility Wells Fargo Bank [Member]	Dec. 31, 2013 Debt Instrument, Measurement Period Three [Member] Revolving Credit Facility Wells Fargo Bank [Member]	Dec. 03, 2013 Debt Instrument, Measurement Period Four [Member] Revolving Credit Facility Wells Fargo Bank [Member]	Jun. 30, 2014 Debt Instrument, Measurement Period Five [Member] Revolving Credit Facility Wells Fargo Bank [Member]
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		68,723,000	67,101,000
Deferred Finance Costs, Noncurrent, Net		2,600,000
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