Credit Facilities (5.00% Notes) (Details)			3 Months Ended		6 Months Ended
	Feb. 24, 2020 USD ($) $ / shares	Apr. 03, 2019 USD ($) day $ / shares	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Mar. 04, 2020	Dec. 31, 2019 USD ($)	Mar. 31, 2019	Aug. 09, 2018 USD ($)	Nov. 02, 2015 USD ($)
Line of Credit Facility [Line Items]
Maximum equity owned by Investor			9.50%		9.50%
Gain (loss) on extinguishment of debt			$ 0	$ (11,756,000)	$ (730,000)	$ (11,756,000)
Carrying value			192,687,000		192,687,000			$ 182,666,000
Stock trigger price (usd per share) | $ / shares		$ 6.61
Convertible notes
Line of Credit Facility [Line Items]
Debt, conversion option			3,600,000		3,600,000
5% Note | Convertible notes
Line of Credit Facility [Line Items]
Debt instrument, stated interest rate		5.00%		5.00%		5.00%			5.00%
Limit on conversion		30.00%					30.00%
Convertible debt, conversion ratio		0.15129
Debt instrument, convertible, face amount of each note that is convertible		$ 1.00
Carrying value			67,200,000		67,200,000
Debt, conversion option			41,200,000		41,200,000
Debt issuance costs, line of credit arrangements, gross			1,200,000		1,200,000
Deferred financing cost			500,000		500,000
Reduction in equity		700,000
Convertible notes payable			30,400,000		30,400,000
Debt issuance costs, gross			400,000		400,000
Debt instrument face amount		25,000,000.0
Mandatory conversion of shares		$ 1,666,666
Convertible debt redemption, consecutive trading days threshold | day		5
Maximum conversion amount		30.00%
5% Note | Convertible notes | Minimum
Line of Credit Facility [Line Items]
Periodic payment, interest					14,700,000
5% Note | Convertible notes | Maximum
Line of Credit Facility [Line Items]
Periodic payment, interest					4,300,000
5% Note | Convertible notes | Two Investors
Line of Credit Facility [Line Items]
Debt instrument face amount		$ 42,000,000.0
5% Note | Face Value Per Note | Two Investors
Line of Credit Facility [Line Items]
Debt instrument face amount		900
Convertible Senior Notes Due 2020
Line of Credit Facility [Line Items]
Debt instrument, stated interest rate										3.25%
Debt instrument face amount										$ 40,500,000
Convertible Senior Notes Due 2020 | Convertible notes
Line of Credit Facility [Line Items]
Debt instrument, stated interest rate											3.25%
Convertible notes payable			100,000		100,000
Debt instrument face amount											$ 125,000,000.0
Convertible Senior Notes Due 2020 | Convertible notes | Three Investors
Line of Credit Facility [Line Items]
Original debt	$ 11,000,000.0
Convertible Senior Notes Due 2020 | Face Value Per Note | Two Investors
Line of Credit Facility [Line Items]
Debt instrument face amount		$ 1,000
New 5.00% Note | Convertible notes
Line of Credit Facility [Line Items]
Debt instrument, stated interest rate		5.00%
Gain (loss) on extinguishment of debt					2,700,000
Carrying value			8,000,000		8,000,000
Debt issuance costs, line of credit arrangements, gross			120,000		120,000
Deferred financing cost			66,000		66,000
Reduction in equity					53,000
Convertible notes payable			4,700,000		4,700,000
Debt issuance costs, gross			$ 100,000		100,000
Periodic payment, principal					0
New 5.00% Note | Convertible notes | Minimum
Line of Credit Facility [Line Items]
Periodic payment, interest					800,000
New 5.00% Note | Convertible notes | Maximum
Line of Credit Facility [Line Items]
Periodic payment, interest					$ 2,900,000
New 5.00% Note | Convertible notes | Three Investors
Line of Credit Facility [Line Items]
Debt instrument face amount	$ 11,000,000.0
Voluntary Conversion
Line of Credit Facility [Line Items]
Stock trigger price (usd per share) | $ / shares		$ 7.271
Voluntary Conversion | Convertible notes
Line of Credit Facility [Line Items]
Convertible debt, conversion ratio	0.4445	0.12103
Debt instrument, convertible, face amount of each note that is convertible	$ 1.00	$ 1.00
Conversion price (USD per share) | $ / shares	$ 2.25	$ 8.2624
Conversion price	110.00%