MSRs - Narrative (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) mortgage_loan_trust	Dec. 31, 2017 USD ($)
Mortgage Servicing Rights MSR [Line Items]
Number of residential mortgage loan securitization trusts | mortgage_loan_trust	4
Mortgage servicing rights
Mortgage Servicing Rights MSR [Line Items]
Residential morgate loan aggregate principal balance | $	$ 407,332,854	$ 338,167,569