Schedule II - Valuation and Qualifying Accounts (Details) - Allowance for Doubtful Accounts - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	$ 814	$ 741	$ 141
Charged to costs and expenses	1,390	943	640
Charged to other accounts	(1,329)	324	0
Reserve adjustments	282	(1,194)	(40)
Balance at end of year	$ 1,157	$ 814	$ 741