Deferred Revenue and Acquisition Related Liabilities, net (Details 2) - Tenant funded tenant improvements [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred Revenue Arrangement [Line Items]
Deferred revenues amortized and recognized as rental income	$ 13,200	$ 13,300	$ 11,000
2017	14,453
2018	13,891
2019	12,349
2020	11,767
2021	10,524
Thereafter	36,505
Deferred revenue	$ 99,489	$ 90,825