Securitizations and Variable Interest Entities - Schedule of Expected Losses (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Carrying Value	$ 75,832	$ 0
Variable Interest Entity, Not Primary Beneficiary, Aggregated Disclosure
Variable Interest Entity [Line Items]
Carrying Value	75,832
Total Exposure	75,832
Variable Interest Entity, Not Primary Beneficiary, Aggregated Disclosure | Rated notes
Variable Interest Entity [Line Items]
Carrying Value	65,189
Total Exposure	65,189
Variable Interest Entity, Not Primary Beneficiary, Aggregated Disclosure | Certificates and other assets
Variable Interest Entity [Line Items]
Carrying Value	10,643
Total Exposure	$ 10,643