Segment Reporting - Narrative (Details) ft² in Millions	12 Months Ended
	Dec. 31, 2016 ft² property security state segment loan	Dec. 31, 2015 security
Segment Reporting Information [Line Items]
Number of operating segments | segment	2
Number of loans held for investment | loan	9
Commercial Mortgage Backed Securities [Member]
Segment Reporting Information [Line Items]
Number of securities held | security	8	10
REI Segment [Member] | Consolidated Properties [Member]
Segment Reporting Information [Line Items]
Number of properties owned | property	4,142
Square feet of property | ft²	93.3
Number of states in which entity operates | state	49
Percentage of rentable space leased	98.30%
Real estate property, weighted average remaining lease term	9 years 10 months 24 days