Schedule II - Valuation and Qualifying Accounts (Details) - Allowance for Doubtful Accounts - 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]
Balance at Beginning of Year		$ 17,230	$ 12,252	$ 11,175
Costs and Expenses		2,123	7,264	6,194
Deductions	[1]	(3,992)	(2,286)	(5,117)
Balance at End of Year		$ 15,361	$ 17,230	$ 12,252

[1] Deductions primarily represent uncollectible balances of accounts receivable written off, net of recoveries.