Segment Reporting - Narrative (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2014 Segment sqft Building	Dec. 31, 2013 Security
Segment Reporting Information [Line Items]
Number of reportable segments	2
Number of owned properties	4,714
Square feet of property	113,800,000
Real Estate Investment Segment [Member]
Segment Reporting Information [Line Items]
Number of loans held for investment	14
Real Estate Investment Segment [Member] | Consolidated Properties [Member]
Segment Reporting Information [Line Items]
Number of owned properties	4,714
Square feet of property	113,800,000
Number of states in which entity operates	49
Percentage of rentable space leased	99.20%
Real estate property, weighted average remaining lease term	11 years 6 months 0 days
Real Estate Investment Segment [Member] | Unconsolidated Properties [Member]
Segment Reporting Information [Line Items]
Number of owned properties	6
Net rentable area (in square feet)	1,600,000
Commercial Mortgage Backed Securities [Member]
Segment Reporting Information [Line Items]
Number of securities acquired		10
Commercial Mortgage Backed Securities [Member] | Real Estate Investment Segment [Member]
Segment Reporting Information [Line Items]
Number of securities acquired	10