Segment Information (Reconciliation of Consolidated Net Operating Income) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	0 Months Ended	3 Months Ended		9 Months Ended
	Sep. 16, 2014	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Reportable_Segments	Sep. 30, 2013
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Consolidated net operating income		$ 89,327	$ 87,231	$ 272,260	$ 257,387
Other income (expense):
Depreciation and amortization		(52,616)	(50,583)	(157,773)	(149,300)
General and administrative expenses		(5,900)	(6,436)	(20,086)	(20,323)
Interest income		528	268	1,298	448
Interest expense		(31,481)	(30,338)	(94,837)	(91,689)
Recognized hedge activity	800	(828)	0	(828)	0
Amortization of deferred financing costs		(1,566)	(1,158)	(3,952)	(3,502)
Interest expense — financing obligation		(273)	(264)	(861)	(693)
Equity in income (loss) of real estate ventures		(486)	714	(733)	3,757
Net gain on disposition of real estate		4,698	0	4,698	0
Gain (Loss) on sale of undepreciated real estate		0	(129)	1,184	(129)
Net gain from remeasurement of investment in RE ventures		0	0	458	7,847
Net gain (loss) on real estate venture transactions		0	0	(417)	3,683
Loss on early extinguishment of debt	2,606	(2,606)	(11)	(2,606)	(1,127)
Provision for impairment on assets held for sale		(1,765)	0	(1,765)	0
Historic tax credit transaction income		(11,853)	(11,853)	(11,853)	(11,853)
Discontinued Operations attributable to common shareholders/unitholders, Basic		$ 0.00	$ 0.00	$ 0.01	$ 0.03
Income from continuing operations		8,885	11,147	7,893	18,212
Income (Loss) from Discontinued Operations		(3)	(59)	918	3,975
Net income		$ 8,882	$ 11,088	$ 8,811	$ 22,187
Number of Reportable Segments				7