Borrowings Borrowings - Phantom (Details)	Jul. 31, 2018	Mar. 31, 2018	Nov. 30, 2017	Feb. 28, 2017
Issuance 2017-A
Debt Instrument [Line Items]
Derivative, Basis Spread on Variable Rate				0.93%
Issuance 2017-B
Debt Instrument [Line Items]
Derivative, Basis Spread on Variable Rate			0.80%
Issuance 2018-A
Debt Instrument [Line Items]
Derivative, Basis Spread on Variable Rate		7.80%
Issuance 2018-B
Debt Instrument [Line Items]
Derivative, Basis Spread on Variable Rate	7.60%
Issuance 2018-C
Debt Instrument [Line Items]
Derivative, Basis Spread on Variable Rate	7.70%