Debt - Additional Information (Details)			1 Months Ended						12 Months Ended
		Jun. 14, 2017 USD ($)	Aug. 31, 2019 USD ($)	Jul. 31, 2019	May 31, 2019 USD ($)	Apr. 30, 2019	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jun. 30, 2020 USD ($) $ / shares	Jun. 30, 2019	Aug. 31, 2017 USD ($)	Apr. 30, 2014	Feb. 28, 2013
Debt
Principal amount of the Notes									$ 202,094,000
Unamortized debt costs									2,796,000
Debt discount costs									9,991,000
Revolving Credit Facility
Debt
Principal amount of the Notes	[1]								28,001,000
Initial borrowing capacity		$ 52,000,000.0
Minimum drawn balance (as a percent)		30.00%
Outstanding revolving credit facility									28,000,000.0
Revolving Credit Facility | Other Assets
Debt
Unamortized debt costs									$ 900,000
90-day LIBOR | Revolving Credit Facility
Debt
Interest rate determination basis									90-day LIBOR
Variable rate (as a percent)		4.50%			3.50%	4.50%
3.75% Convertible Senior Notes due 2022
Debt
Aggregate principal amount of debt issued											$ 85,000,000.0
Interest rate (as a percent)									3.75%	3.75%	3.75%
Conversion rate, number of shares to be issued per $1000 of principal amount (in shares)									174.8252
Principal amount used for debt instrument conversion ratio									$ 1,000
Conversion price (in dollars per share) | $ / shares									$ 5.72
Repurchase price, as a percentage of the principal amount, in the event of a fundamental change, as defined in Indenture									100.00%
Principal amount of the Notes									$ 85,000,000
Unamortized debt costs									1,922,000
Debt discount costs									6,680,000
3.50% Convertible Notes
Debt
Interest rate (as a percent)													3.50%
3.50% Series A Convertible Senior Notes
Debt
Interest rate (as a percent)												3.50%
Exchange | 3.75% Convertible Senior Notes due 2022
Debt
Aggregate principal amount of debt issued											$ 53,000,000.0
Exchange | 3.50% Convertible Notes due 2018 and 3.5% Series A Senior Notes due February 2018
Debt
Aggregate principal amount of debt issued											47,000,000.0
Repurchase
Debt
Repurchase/Retirement of existing notes											28,000,000.0
Repurchase | 3.75% Convertible Senior Notes due 2022
Debt
Aggregate principal amount of debt issued											$ 32,000,000.0
Revolving Credit Agreement | Revolving Credit Facility
Debt
Reduced borrowing capacity								$ 32,000,000.0
Term Loan Facility due December 2022
Debt
Principal amount of the Notes									89,093,000
Unamortized debt costs									874,000
Debt discount costs									$ 3,311,000
Term Loan Facility due December 2022 | Term loan
Debt
Initial term loan borrowing capacity								40,000,000.0
Additional term loan borrowing capacity								$ 20,000,000.0
Loan prepayment fees for first year (percentage)								3.00%
Loan prepayment fees for second year (percentage)								2.00%
Loan prepayment fees for third year (percentage)								1.00%
Term of loan (in months)								60 months
Term of interest payable (in months)								24 months
Administrative fee payable on term loan as a percentage								0.25%
Final payment of administrative fee payable on term loan as a percentage								4.00%
Debt instrument amount withdrawn							$ 5,000,000.0
Debt instrument scheduled commitment extended termination date							Jun. 30, 2019
Debt instrument remaining unfunded commitment amount							$ 15,000,000.0
Term Loan Facility due December 2022 | 90-day LIBOR | Term loan
Debt
Interest rate determination basis									90-day LIBOR
Variable rate (as a percent)								6.75%
Term Loan Facility Due May 2024 | Term loan
Debt
Principal amount of the Notes									$ 89,100,000
Debt instrument increased commitment amount			$ 25,000,000		$ 500,000
Debt discount costs			$ 1,600,000		$ 1,500,000
Term Loan Facility Due May 2024 | 90-day LIBOR | Term loan
Debt
Interest rate determination basis									90-day LIBOR
Variable rate (as a percent)			6.75%	5.50%	5.50%	6.75%

[1] Unamortized debt costs of $0.9 million recorded in other assets on the consolidated balance sheet.