Investment Securities, at Fair Value - Narrative (Details)		1 Months Ended	12 Months Ended
	Feb. 07, 2014 USD ($) security	Sep. 30, 2014 USD ($) security	Dec. 31, 2016 USD ($) security	Dec. 31, 2015 USD ($) security
Schedule of Available-for-sale Securities [Line Items]
Investment securities, at fair value			$ 47,215,000	$ 53,304,000
CMBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of securities owned | security			8	10
Investment securities, at fair value	$ 151,200,000		$ 47,215,000	$ 53,304,000
Number of securities paid in full prior to maturity | security			2
Carrying value of security paid in full (less than)			$ 100,000
Number of securities with fair value below amortized cost | security			5
Other-than-temporary impairment losses			$ 0
Number of securities sold | security		15
Proceeds from sale of securities		$ 158,000,000
CMBS [Member] | Minimum [Member]
Schedule of Available-for-sale Securities [Line Items]
Interest rate			5.88%
CMBS [Member] | Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Interest rate			8.95%
CMBS [Member] | Cole Real Estate Investments, Inc. [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of securities acquired | security	15
Other Income [Member]
Schedule of Available-for-sale Securities [Line Items]
Gain on sale of investment securities			$ 0	$ 65,000
Other Income [Member] | CMBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Gain on sale of securities		$ 6,200,000