Schedule II - Consolidated 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 period		$ 6,938	$ 4,644	$ 4,993
Charged to costs and expenses		1,191	3,302	1,183
Transferred from (to) allowance for accounts / notes receivable		0	0	0
Deductions	[1]	(423)	(1,008)	(1,532)
Balance at end of period		$ 7,706	$ 6,938	$ 4,644

[1] Uncollectible accounts written off, net of recoveries and adjustments to estimates for the allowance accounts.