MSRs - Narrative (Details)	Dec. 31, 2017 USD ($) mortgage_loan_trust	Dec. 31, 2016 USD ($)
Mortgage Servicing Rights MSR [Line Items]
Residential morgate loan aggregate principal balance	$ 0	$ 2,849,981
Number of residential mortgage loan securitization trusts \| mortgage_loan_trust	3
TRS Activity
Mortgage Servicing Rights MSR [Line Items]
Residential morgate loan aggregate principal balance	$ 338,167,569

Total carrying amount of mortgage loans as of the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
-Subparagraph (SX 210.5-04.(c) Schedule IV)
-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29.6)
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

Name:	us-gaap_MortgageLoansOnRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant