Commitments and Contingencies - Future Minimum Rental Payments (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
2018 (remaining)	$ 1,431,000
2019	1,968,000
2020	1,963,000
2021	1,963,000
2022	1,917,000
2023 and thereafter	33,776,000
Total	43,018,000
Other Expenses [Abstract]
Operating ground lease expense	$ 409,000	$ 311,000