CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Allowance for doubtful accounts	$ 2,531,000	$ 2,636,000
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)	53,845,427	53,774,221
Common stock, shares outstanding (in shares)	53,845,427	53,774,221
Convertible Notes Payable
Face amount of the Notes	$ 167,110,000	$ 160,090,000
Senior Notes, due December 2019 \| Convertible Notes Payable
Stated interest rate	4.75%	4.75%
Face amount of the Notes	$ 75,090,000	$ 75,090,000
Senior Notes, due December 2019 \| Convertible Notes Payable
Stated interest rate	3.75%	3.75%
Face amount of the Notes	$ 13,022,000	$ 15,702,000
Revolving Credit Facility \| Line of Credit
Face amount of the Notes	20,000,000	15,000,000
Term Loan \| 2023 Term Loan \| Line of Credit
Face amount of the Notes	$ 72,020,000	$ 70,000,000

A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible.

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