Debt - Additional Information (Details)					1 Months Ended				3 Months Ended		6 Months Ended
	Feb. 07, 2018 shares	Feb. 01, 2018 USD ($) shares	Jan. 30, 2018 USD ($)	Jun. 14, 2017 USD ($)	Dec. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($)	Apr. 30, 2014 USD ($) $ / shares	Feb. 28, 2013 USD ($) $ / shares	Dec. 31, 2018 USD ($) $ / shares	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) $ / shares	Aug. 31, 2017 USD ($)
Debt
Common stock value					$ 88,000				$ 88,000	$ 86,000	$ 88,000
Principal amount of the Notes					152,539,000				$ 152,539,000	$ 148,685,000	152,539,000
Minimum
Debt
Fixed Charge Coverage Ratio									50.00%	75.00%
Revolving Credit Facility
Debt
Principal amount of the Notes					22,539,000				$ 22,539,000	$ 23,685,000	22,539,000
Initial borrowing capacity				$ 52,000,000
Minimum drawn balance (as a percent)				30.00%
Outstanding revolving credit facility					22,500,000				22,500,000		$ 22,500,000
90-day LIBOR | Revolving Credit Facility
Debt
Interest rate determination basis											90-day LIBOR
Variable rate (as a percent)				4.50%
Repurchase
Debt
Repurchase/Retirement of existing notes												$ 28,000,000
Revolving Credit Agreement | Revolving Credit Facility
Debt
Reduced borrowing capacity						$ 32,000,000
Combined Term Loan and Credit Agreement Member
Debt
Debt agreement Amendment date											Jul. 31, 2018
Term Loan Facility due December 2022
Debt
Principal amount of the Notes					45,000,000				45,000,000	$ 40,000,000	$ 45,000,000
Term Loan Facility due December 2022 | Term loan
Debt
Principal amount of the Notes					45,000,000				$ 45,000,000		$ 45,000,000
Initial term loan borrowing capacity						40,000,000
Additional term loan borrowing capacity						$ 20,000,000
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Debt instrument amount withdrawn					$ 5,000,000
Debt instrument scheduled commitment extended termination date					Jun. 30, 2019
Debt instrument remaining unfunded commitment amount					$ 15,000,000
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%
3.50% Convertible Senior Notes
Debt
Interest rate (as a percent)					3.50%			3.50%	3.50%		3.50%
Conversion rate, number of shares to be issued per $1000 of principal amount (in shares)								187.6877
Principal amount used for debt instrument conversion ratio								$ 1,000
Conversion price (in dollars per share) | $ / shares								$ 5.33
Repayment of convertible debt and accrued interest		$ 13,200,000	$ 13,000,000
Common stock value			300,000
Period of volume weighted averaging price which is used to determine total number of shares	3 days
3.50% Convertible Senior Notes | Other expense, net
Debt
Extinguishment of debt			$ 300,000
3.50% Convertible Senior Notes | Common Stock
Debt
Common stock shares issued to note holders | shares	253,000
3.50% Series A Convertible Senior Notes
Debt
Interest rate (as a percent)							3.50%
Conversion rate, number of shares to be issued per $1000 of principal amount (in shares)							187.6877
Principal amount used for debt instrument conversion ratio							$ 1,000
Conversion price (in dollars per share) | $ / shares							$ 5.33
Repayment of convertible debt and accrued interest		$ 27,000,000
3.50% Series A Convertible Senior Notes | Common Stock
Debt
Common stock shares issued to settle Convertible Notes | shares		1,252
3.75% Convertible Senior Notes due 2022
Debt
Interest rate (as a percent)					3.75%				3.75%	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				$ 1,000		$ 1,000
Conversion price (in dollars per share) | $ / shares					$ 5.72				$ 5.72		$ 5.72
Aggregate principal amount of debt issued												$ 85,000,000
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				$ 85,000,000	$ 85,000,000	$ 85,000,000
3.75% Convertible Senior Notes due 2022 | Exchange
Debt
Aggregate principal amount of debt issued												53,000,000
3.75% Convertible Senior Notes due 2022 | Repurchase
Debt
Aggregate principal amount of debt issued												32,000,000
3.50% Convertible Notes due 2018 and 3.5% Series A Senior Notes due February 2018
Debt
Interest rate (as a percent)					3.50%				3.50%		3.50%
3.50% Convertible Notes due 2018 and 3.5% Series A Senior Notes due February 2018 | Exchange
Debt
Aggregate principal amount of debt issued												$ 47,000,000