Fair Value of Financial Instruments - Amortized Cost Basis by Year of Origination and Credit Quality Indicator (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
2021	$ 0
2020	5,509
2019	16,865
2018	25,075
Total	47,449	$ 47,690
Current-period write-offs	0
Current-period recoveries	0
Current-period net write-offs	0
1-2 internal grade
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	5,509
2019	8,369
2018	18,487
Total	32,365
3-4 internal grade
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019	8,496
2018	6,588
Total	15,084
5 internal grade
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019	0
2018	0
Total	0
6 internal grade
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019	0
2018	0
Total	0
7 internal grade
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019	0
2018	0
Total	$ 0