CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Allowance for doubtful accounts	$ 2,293,000	$ 2,208,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	53,899,495	53,850,427
Common stock, shares outstanding (in shares)	53,899,495	53,850,427
Convertible Notes Payable
Face amount of the Notes	$ 216,341,000	$ 213,959,000
Senior Notes, due May 2023 | Convertible Notes Payable
Stated interest rate	4.75%
Face amount of the Notes	$ 66,090,000	66,090,000
Series B Senior Unsecured Convertible Notes | Convertible Notes Payable
Face amount of the Notes	34,405,000	34,405,000
Senior Notes, due February 2023 | Convertible Notes Payable
Face amount of the Notes	90,846,000	88,464,000
Revolving Credit Facility | Line of Credit
Face amount of the Notes	$ 25,000,000	$ 25,000,000