Allowance for Credit Losses - Components of Allowance for Credit Losses (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss	$ 91,847	$ 49,529	$ 30,616	$ 32,582	$ 30,323
Financial asset acquired with credit deterioration
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss	0	0	6
Total allowance for credit losses
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss	90,397	48,730	29,675
Qualitative and forecast factor allowance
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss	61,935	21,830	12,146
Quantitative (Cohort) model allowance reserves
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss	28,462	26,900	17,529
Allowance for individually evaluated loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Allowance for credit loss	$ 1,450	$ 799	$ 935