Supplemental Disclosure to Statements of Cash Flows (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Supplemental Cash Flow Information [Abstract]
Write off of fully depreciated property and deferred costs	$ 31,322	$ 23,180
Write off of depreciated property and deferred costs due to sale	132,707	49,618
Unrealized losses on cash flow hedge, non cash transaction	(990)	0
Write-off of preferred units costs due to redemption	0	1,236
Increase in investments in and advances to unconsolidated joint ventures due to disposition activity	(11,948)	0
Changes in accrued development capital expenditures	$ 7,854	$ 12,869