Schedule II - Valuation and Qualifying Accounts (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-09, Allowance, Credit Loss [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
SEC Schedule, 12-09, Valuation Allowances and Reserves, Increase (Decrease) Adjustment	$ 633,000	$ 2,851,000	$ 7,256,000
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	2,899,000	7,485,000	871,000
Deductions	(3,125,000)	(7,437,000)	(642,000)
Ending balance		2,899,000	7,485,000
Allowance for doubtful accounts	407,000	2,899,000	7,485,000
SEC Schedule, 12-09, Allowance, Loan and Lease Loss [Member]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
SEC Schedule, 12-09, Valuation Allowances and Reserves, Increase (Decrease) Adjustment	0	0	0
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	0	0	0
Deductions	0	0	0
Ending balance	$ 0	$ 0	$ 0