Segment Information Segment Information (Reconciliation of Consolidated Net Operating Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Reportable_Segments	Sep. 30, 2012
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Consolidated net operating income	$ 87,288	$ 80,953	$ 257,865	$ 242,910
Less:
Interest expense	(30,338)	(32,620)	(91,689)	(99,745)
Interest expense — amortization of deferred financing costs	(1,158)	(1,218)	(3,502)	(3,790)
Depreciation and amortization	(50,613)	(46,955)	(149,423)	(142,262)
Interest expense — financing obligation	(264)	(230)	(693)	(608)
General and administrative expenses	(6,436)	(6,080)	(20,322)	(18,209)
Net gain (loss) on sale of undepreciated real estate	(129)	0	(129)	0
Loss On Real Estate Venture Formation	0	950	0	950
Loss on early extinguishment of debt	(11)	(51)	(1,127)	(1,549)
Plus:
Interest income	268	311	448	2,631
Historic tax credit transaction income	11,853	11,840	11,853	11,840
Equity in income of real estate ventures	714	500	3,757	1,382
Gain from remeasurement of investment in a real estate venture	0	0	7,847	0
Net gain on real estate venture transactions	0	0	3,683	0
Income (Loss) from continuing operations	11,174	5,500	18,568	(8,350)
Income (Loss) from Discontinued Operations	(86)	11,589	3,619	41,577
Net income	$ 11,088	$ 17,089	$ 22,187	$ 33,227
Number of Reportable Segments			7