Valuation and Qualifying Accounts - Summarized Activity in Allowances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 7,700	$ 12,700	$ 7,400
Additions Charged to Expense	14,000	12,500	16,600
Additions Charged Against Revenues	0	0	5,500
Deductions from the Reserve	(13,700)	(11,300)	(16,800)
Reclassification to Accounts Payable and Accrued Liabilities	0	(6,200)	0
Balance at End of Year	$ 8,000	$ 7,700	$ 12,700