Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Schedule of amounts due under lease commitments

Amounts due under ground and operating lease commitments are as follows (in thousands):

2018	$	2,669
2019	2,569
2020	2,474
2021	2,453
2022	2,396
Thereafter	195,721
	$	208,282