Securitizations and Variable Interest Entities - Schedule of Expected Losses (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Carrying Value	$ 45,192	$ 0
Variable Interest Entity, Not Primary Beneficiary, Aggregated Disclosure
Variable Interest Entity [Line Items]
Carrying Value	45,192
Total Exposure	45,192
Variable Interest Entity, Not Primary Beneficiary, Aggregated Disclosure | Rated notes
Variable Interest Entity [Line Items]
Carrying Value	38,893
Total Exposure	38,893
Variable Interest Entity, Not Primary Beneficiary, Aggregated Disclosure | Certificates and other assets
Variable Interest Entity [Line Items]
Carrying Value	6,299
Total Exposure	$ 6,299