Quarterly Financial Information - Net (Loss) Income Available to Unitholders and Basic and Diluted Earnings Per Unit (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Total Revenues	$ 78,777	$ 76,210	$ 74,082	$ 73,536	$ 71,540	$ 69,377	$ 70,019	$ 68,791	$ 302,605	$ 279,727	$ 266,155
Equity in Income of Other Real Estate Partnerships	3,826	4,775	2,516	3,094	2,486	4,546	2,399	2,172	14,211	11,603	7,756
Equity in Income (Loss) of Joint Ventures	(9)	(14)	556	2,966	17	72	27	20	3,499	136	1,559
Income (Loss) from Continuing Operations	8,043	10,145	3,281	4,218	2,284	4,958	(1,548)	299	25,687	5,993	(25,181)
Income (Loss) from Discontinued Operations	11,702	12,073	946	860	19,809	3,559	12,941	(1,689)	25,581	34,620	18,986
Gain (Loss) on Sale of Real Estate, Net of Income Tax	(83)	0	0	0	337	221	0	262	(83)	820	3,777
Net Income (Loss)	19,662	22,218	4,227	5,078	22,430	8,738	11,393	(1,128)	51,185	41,433	(2,418)
Preferred Unit Distributions	0	0	0	(1,019)	(1,227)	(1,392)	(2,277)	(3,837)	(1,019)	(8,733)	(18,947)
Redemption of Preferred Units	0	0	0	(1,462)	0	(2,121)	(3,546)	0	(1,462)	(5,667)	(1,804)
Net Income (Loss) Available to Unitholders and Participating Securities	19,662	22,218	4,227	2,597	21,203	5,225	5,570	(4,965)	48,704	27,033	(23,169)
Income from Continuing Operations Allocable to Participating Securities	(32)	(41)	(33)	(21)	(6)	(13)	0	(36)	(83)	0	0
Income from Discontinued Operations Allocable to Participating Securities	(47)	(49)	(10)	(10)	(85)	(29)	(42)	0	(92)	(162)	0
Net Income (Loss) Available to Unitholders	$ 19,583	$ 22,128	$ 4,184	$ 2,566	$ 21,112	$ 5,183	$ 5,528	$ (5,001)	$ 48,529	$ 26,871	$ (23,169)
Basic Earnings Per Unit:
Income (Loss) from Continuing Operations Available to Unitholders	$ 0.07	$ 0.09	$ 0.03	$ 0.01	$ 0.01	$ 0.01	$ (0.06)	$ (0.03)
Income (Loss) from Discontinued Operations Attributable to Unitholders	$ 0.10	$ 0.10	$ 0.01	$ 0.01	$ 0.18	$ 0.03	$ 0.11	$ (0.02)
Net Income (Loss) Available to Unitholders	$ 0.17	$ 0.19	$ 0.04	$ 0.02	$ 0.19	$ 0.04	$ 0.05	$ (0.05)
Diluted Earnings Per Unit:
Income (Loss) from Continuing Operations Available to Unitholders	$ 0.07	$ 0.09	$ 0.03	$ 0.01	$ 0.01	$ 0.01	$ (0.06)	$ (0.03)
Income (Loss) from Discontinued Operations Attributable to Unitholders	$ 0.10	$ 0.10	$ 0.01	$ 0.01	$ 0.17	$ 0.03	$ 0.11	$ (0.02)
Net Income (Loss) Available to Unitholders	$ 0.17	$ 0.19	$ 0.04	$ 0.02	$ 0.18	$ 0.04	$ 0.05	$ (0.05)
Weighted Average Units —Basic	114,512	114,512	114,278	114,245	114,089	114,089	112,808	105,477	114,388	111,646	96,509
LTIP Unit Awards	287	199	589	539	485	407	0	0	403	0	0
Weighted Average Units - Diluted	114,799	114,711	114,867	114,784	114,574	114,496	112,808	105,477	114,791	111,646	96,509