Receivables and Allowance for Credit Losses - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended		12 Months Ended
	Jun. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Notes Receivable and Allowance for Losses [Line Items]
Loan reserves		$ 20,039		$ 19,484	$ 4,556
Loans and financing receivable		67,755		95,785
Variable Interest Entity, Not Primary Beneficiary
Notes Receivable and Allowance for Losses [Line Items]
Loans and financing receivable		138,500		119,300
SG&A expenses
Notes Receivable and Allowance for Losses [Line Items]
Provision (reversal) of credit losses		2,200	$ 10,400
Marketing and reservation system expenses
Notes Receivable and Allowance for Losses [Line Items]
Provision (reversal) of credit losses		4,200	$ 18,000
Senior Notes
Notes Receivable and Allowance for Losses [Line Items]
Acquired a senior note with collateral	$ 17,900
Collateral-Dependent Loans
Notes Receivable and Allowance for Losses [Line Items]
Loan reserves		9,100		7,800
Impaired Loans
Notes Receivable and Allowance for Losses [Line Items]
Average notes receivable, nonaccrual status		68,700		28,900
Interest Rate Below Market Reduction | Variable Interest Entity, Not Primary Beneficiary
Notes Receivable and Allowance for Losses [Line Items]
Loans and financing receivable		13,100		13,100
Receivable with imputed interest, discount		$ 400		$ 800