CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Allowance for doubtful accounts	$ 2,636,000	$ 2,185,000
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)	53,774,221	53,400,281
Common stock, shares outstanding (in shares)	53,774,221	53,400,281
Convertible Notes Payable
Face amount of the Notes	$ 160,090,000	$ 0
Convertible Notes Payable
Stated interest rate	3.75%
Revolving Credit Facility
Stated interest rate	4.75%
Revolving Credit Facility \| Convertible Notes Payable
Face amount of the Notes	$ 15,000,000	0
2023 Term Loan
Stated interest rate	4.75%
Senior Notes, due December 2019
Stated interest rate	3.75%
Senior Notes, due December 2019 \| Convertible Notes Payable
Face amount of the Notes	$ 15,702,000	$ 143,750,000
Stated interest rate	3.75%	3.75%

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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