Securitizations and Variable Interest Entities - Schedule of Cost and Fair Value of Securities (Details) - Variable Interest Entity, Not Primary Beneficiary, Aggregated Disclosure $ in Thousands	Jun. 30, 2019 USD ($)
Variable Interest Entity [Line Items]
Amortized Cost	$ 45,015
Fair Value	45,192
Rated notes
Variable Interest Entity [Line Items]
Amortized Cost	38,684
Fair Value	38,893
Certificates and other assets
Variable Interest Entity [Line Items]
Amortized Cost	6,331
Fair Value	$ 6,299