Schedule II - Valuation and Qualifying Accounts (Details) - SEC Schedule, 12-09, Allowance for Doubtful Accounts [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount	$ 6,285	$ 4,526	$ 4,431
Additions Charged Against Operations	3,298	3,807	751
Adjustments to Valuation Accounts	0	0	0
Uncollectible Accounts Written‑off	(1,989)	(2,048)	(656)
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount	$ 7,594	$ 6,285	$ 4,526