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 Period	$ 0	$ 44,730	$ 59,689
Write-Off of Receivables	0	(30,515)	(41,567)
Charged to Costs and Expenses	0	23,697	26,608
Balance at End of Period	$ 0	$ 37,912	$ 44,730