Litigation and Other Related Contingencies (Details)		6 Months Ended
	May 06, 2019	Oct. 31, 2019 USD ($) securities lawsuit	Apr. 30, 2019 USD ($)	Oct. 31, 2018 USD ($)	Sep. 30, 2016 loan	Sep. 28, 2012 loan	May 31, 2012 loan
Commitments and Contingencies Disclosure [Abstract]
Loss contingency accrual		$ 1,600,000	$ 1,900,000	$ 3,000,000.0
Loss Contingencies [Line Items]
Original loans collateralized | loan							7,500
Number of loans sold to the trust | loan						96
Loans sold to trust, with claims of breach of contract and indemnity | loan					649
Securitization transactions | securities		39
SCC
Commitments and Contingencies Disclosure [Abstract]
Loss contingency accrual		$ 0	$ 0	$ 0
Loss Contingencies [Line Items]
Original principal amount of loans securitized		14,000,000,000
Principal assets of SCC		280,000,000
SCC | Claims with Knowledge of Outstanding Principal Amount
Loss Contingencies [Line Items]
Initial principal on loans securitized		$ 2,900,000,000
Free File Litigation
Loss Contingencies [Line Items]
Eligibility period prior to filing complaint	4 years
MGRID LLC v. Merrill Lynch Mortgage Lending Inc
Loss Contingencies [Line Items]
Number of lawsuits | lawsuit		21