Supplemental Disclosure to Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Significant Noncash Transactions [Line Items]
Write-off of costs related to early debt extinguishment	$ 0	$ 219	$ 0
Unrealized gain (loss) on cash flow hedge	605	410	(488)
Capitalized equity-based compensation	1,096	1,221	876
Redemption of noncontrolling interests - common units	152	132	0
Continuing Operations [Member]
Other Significant Noncash Transactions [Line Items]
Write-off of fully depreciated/amortized property and deferred costs - properties included in continuing operations	16,568	23,331	27,202
Write-off of depreciated property and deferred costs due to sale/demolition - properties included in continuing operations	15,760	461,480	252,017
Changes in accrued development capital expenditures - properties included in continuing operations	12,341	(11,274)	12,935
Discontinued Operations [Member]
Other Significant Noncash Transactions [Line Items]
Write-off of fully depreciated/amortized property and deferred costs - properties included in continuing operations	15,368	18,075	15,137
Write-off of depreciated property and deferred costs due to sale/demolition - properties included in continuing operations	17,335	0	0
Changes in accrued development capital expenditures - properties included in continuing operations	$ 0	$ (94)	$ (971)