Fair Value Measures - Schedule of assets measured at fair value on a recurring basis (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Assets:
Derivative assets	$ 848	$ 627
Fair Value, Measurements, Recurring [Member]
Assets:
CMBS	35,741	40,974
Derivative assets	848	627
Investment in Cole REITs	7,844
Total assets	44,433	41,601
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Assets:
CMBS	0	0
Derivative assets	0	0
Investment in Cole REITs	0
Total assets	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Assets:
CMBS	0	0
Derivative assets	848	627
Investment in Cole REITs	0
Total assets	848	627
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Assets:
CMBS	35,741	40,974
Derivative assets	0	0
Investment in Cole REITs	7,844
Total assets	$ 43,585	$ 40,974