Allowance for Doubtful Accounts - Allowance for doubtful accounts (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019	Jan. 01, 2020
Accounts receivable
Accounts receivable, Allowance for doubtful accounts, beginning balance	$ 66,299	$ 39,903
Write-Offs	(2,475)	(16,871)
Bad Debt Expense	967	5,050
Accounts receivable, Allowance for doubtful accounts, ending balance	64,791	64,791
Notes receivable
Notes receivable, Allowance for doubtful accounts, beginning balance	17,302	17,302
One-time adjustment	17,302	12,490
Write-Offs	(253)	(2,421)
Bad Debt Expense	(132)	1,706
Notes receivable, Allowance for doubtful accounts, ending balance	17,687	12,490
Allowance for doubtful accounts, beginning balance	83,986	52,393
Write-Offs	(2,728)	(19,292)
Bad Debt Expense	835	6,756	$ 22,980
Allowance for doubtful accounts, ending balance	82,093	82,093
Accounts receivable recovered after write off	100	900
Cumulative Impact from Adopting ASC 326 Guidance
Notes receivable
One-time adjustment				$ 5,527
Standard notes receivable
Notes receivable
Notes receivable, Allowance for doubtful accounts, beginning balance	11,484	11,484
One-time adjustment	11,484	6,667
Write-Offs	(253)	(1,974)
Bad Debt Expense	(132)	1,555
Notes receivable, Allowance for doubtful accounts, ending balance	11,869	6,667
Standard notes receivable | Cumulative Impact from Adopting ASC 326 Guidance
Notes receivable
One-time adjustment				5,236
Elevated risk notes receivable
Notes receivable
Notes receivable, Allowance for doubtful accounts, beginning balance	5,818	5,818
One-time adjustment	5,818	5,823
Write-Offs	0	(447)
Bad Debt Expense	0	151
Notes receivable, Allowance for doubtful accounts, ending balance	$ 5,818	$ 5,823
Elevated risk notes receivable | Cumulative Impact from Adopting ASC 326 Guidance
Notes receivable
One-time adjustment				$ 291