Commitments, Off-Balance Sheet Arrangements and Contingent Liabilities, Contingent Liabilities (Details)				1 Months Ended	12 Months Ended
	May 06, 2020 USD ($)	May 03, 2019 LoanOriginator Plaintiff	Dec. 08, 2017 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Mar. 31, 2020 USD ($)	May 31, 2019 USD ($)	Mar. 31, 2019 Claimant
Loss Contingencies [Abstract]
Number of claimants | Claimant								95
Proposed settlement payment					$ 4,250,000
Herrington v. Waterstone Mortgage Corporation [Member]
Loss Contingencies [Abstract]
Amount of damages awarded to plaintiff			$ 7,300,000
Attorney fees	$ 1,100,000		3,300,000	$ 1,100,000
Incentive fees			$ 20,000
Amount of damages to be paid							$ 14,952
Reserve for losses						$ 1,100,000
Raeleen Johnson v. Waterstone Mortgage Corporation [Member]
Loss Contingencies [Abstract]
Number of loan originators | LoanOriginator		38
Number of plaintiffs | Plaintiff		30
Herrington, Raeleen Johnson and Arbitrations [Member]
Loss Contingencies [Abstract]
Reserve for losses				$ 4,250,000