Summary of Significant Accounting Policies (Additional Information 1) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary Of Significant Accounting Policies [Line Items]
Impairment losses	$ 1,600	$ 0	$ 0
Goodwill	173,843	173,843
Amortization of the deferred financing costs	3,640	3,285	3,181
Written off unamortized debt cost			500
Amortization of deferred leasing costs total	18,500	15,200	11,800
Deferred income	25,305	21,993	17,000
Amortization of deferred revenue	10,700	9,400	6,000
Company recorded equity-based compensation expense net of repurchased awards and forfeits	13,900	10,600	7,000
Amount of the straight-line rent receivable on the balance sheets included in rents and other receivables, net	23,400	17,300
Unsecured Revolving Credit Facility
Summary Of Significant Accounting Policies [Line Items]
Amortization of the deferred financing costs	3,600	3,300	$ 3,200
Written off unamortized debt cost	$ 5,200	$ 200