Notes Receivable and Allowance for Losses - Summary of activity related to allowance for losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	$ 4,556	$ 4,685
Reserves established from adoption of Topic 326	19,484	4,685
Provisions for credit losses	7,634	0
Write-offs	(1,054)	(129)
Ending balance	19,484	4,556
Cumulative Effect, Period of Adoption, Adjustment
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	8,348
Reserves established from adoption of Topic 326	$ 8,348	8,348
Ending balance		$ 8,348