Loans to Bank Customers - Credit Quality Indicators (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Outstanding Loans [Line Items]
Nonperforming loans	$ 20,423	$ 21,417
Non-Classified
Outstanding Loans [Line Items]
Nonperforming loans	19,855	19,921
Classified
Outstanding Loans [Line Items]
Nonperforming loans	1,210	2,662
Residential | Non-Classified
Outstanding Loans [Line Items]
Nonperforming loans	3,571	4,241
Residential | Classified
Outstanding Loans [Line Items]
Nonperforming loans	250	290
Commercial | Non-Classified
Outstanding Loans [Line Items]
Nonperforming loans	1,901	158
Commercial | Classified
Outstanding Loans [Line Items]
Nonperforming loans	0	0
Installment | Non-Classified
Outstanding Loans [Line Items]
Nonperforming loans	455	1,058
Installment | Classified
Outstanding Loans [Line Items]
Nonperforming loans	139	189
Secured credit card | Non-Classified
Outstanding Loans [Line Items]
Nonperforming loans	13,928	14,464
Secured credit card | Classified
Outstanding Loans [Line Items]
Nonperforming loans	$ 821	$ 2,183