Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Carrying Value and Estimated Fair Value of Financial Instruments

The following table presents the financial instruments that are not carried at fair value but which require fair value disclosure:

	December 31,				December 31,
	2016				2017
	Carrying		Fair		Carrying		Fair
	amount		value		amount		value
Cash and cash equivalents	$	33,153	$	33,153	$	29,655	$	29,655
Accounts receivable, net		10,347		10,347		10,446		10,446
Accounts payable		2,614		2,614		2,272		2,272