Customer Notes Receivable - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan systems not yet placed in service	$ 85,600,000	$ 37,100,000
Interest income	23,741,000	12,483,000	$ 6,450,000
Customer notes receivable not accruing interest	0	0
Interest income for nonaccrual loans	0
Amortized cost	8,600,000	5,000,000.0
Customer notes receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income	23,200,000	11,600,000
Accrued investment income receivable	1,200,000	$ 869,000
Accrued investment income receivable, written off	$ 0
Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Agreement term	10 years
Median
Accounts, Notes, Loans and Financing Receivable [Line Items]
Agreement term	15 years
Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Agreement term	25 years
Loan revenue | Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Agreement term	10 years
Loan revenue | Median
Accounts, Notes, Loans and Financing Receivable [Line Items]
Agreement term	15 years
Loan revenue | Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Agreement term	25 years