Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands		9 Months Ended	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Remaining purchase discount on loans	$ 50,958
Interest receivable		$ 56,382
Accounting standards update [Extensible List]		us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201613Member
Cumulative Effect, Period Of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Remaining purchase discount on loans	$ (5,469)