Real Estate Investments - Mortgage Loans - Early Payoffs (Details) $ in Thousands	12 Months Ended
Dec. 31, 2018 USD ($) loan	Dec. 31, 2017 USD ($) loan
Early mortgage loan payoffs
Early Principal Payoff	$ 1,086	$ 16,665
AZ/MI/PA/TX/VA \| Mortgage Loans
Early mortgage loan payoffs
Early Principal Payoff		$ 10,795
Number of Loans \| loan		4
UT \| Mortgage Loans
Early mortgage loan payoffs
Early Principal Payoff	$ 1,086
Number of Loans \| loan	1

Number of mortgage loans within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Footnote 3
-Subsection 29

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Footnote 3))
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

Name:	srt_MortgageLoansOnRealEstateNumberOfLoans
Namespace Prefix:	srt_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration