Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Balance at beginning of year	$ 499	$ 502	$ 512
Provision for bad debt	126	16	63
Write-offs, net of recoveries	(58)	(19)	(73)
Balance at end of year	$ 567	$ 499	$ 502