Net Income Per Common Share (Details) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Basic:
Income from operations available to common stockholders	$ 8,505,000		$ 6,224,000		$ 22,096,000		$ 28,544,000
Income from operations available to common stockholders: weighted average common shares (in shares)	33,121,728		29,690,910		32,215,549		29,334,359
Income from operations available to common stockholders: per share amount (in dollars per share)	$ 0.26		$ 0.21		$ 0.69		$ 0.97
Income from discontinued operations available to common stockholders	(818,000)		153,000		4,336,000		442,000
Income from discontinued operations available to common stockholders: weighted average common shares (in shares)	33,122		29,691		32,216		29,334
Income from discontinued operations available to common stockholders: per share amount (in dollars per share)	$ (0.03)		$ 0		$ 0.13	[1]	$ 0.02
Total income	7,687,000		6,377,000		26,432,000		28,986,000
Effect of Dilutive Securities: Income	0	[1],[2]	0	[1],[2]	0	[1],[2]	0	[1],[2]
Effect of Dilutive Securities: weighted average common shares (in shares)	87	[1],[2]	71	[1],[2]	89	[1],[2]	65	[1],[2]
Total income per common share amount (in dollars per share)	$ 0.23		$ 0.21		$ 0.82		$ 0.99
Diluted:
Income from operations available to common stockholders	8,505,000		6,224,000		22,096,000	[2]	28,544,000	[2]
Income from operations available to common stockholders: weighted average common shares (in shares)	33,209,289		29,762,420		32,304,686	[1]	29,398,637	[1]
Income from operations available to common stockholders: per share amount (in dollars per share)	$ 0.26		$ 0.21		$ 0.69	[2]	$ 0.97	[2]
Income from discontinued operations available to common stockholders	(818,000)		153,000		4,336,000		442,000
Income from discontinued operations available to common stockholders: weighted average common shares (in shares)	33,209		29,762		32,305		29,399
Income from discontinued operations available to common stockholders: per share amount (in dollars per share)	$ (0.03)		$ 0		$ 0.13		$ 0.02
Total income (diluted)	7,687,000		6,377,000		26,432,000		28,986,000
Total income per common share amount (in dollars per share)	$ 0.23		$ 0.21		$ 0.82		$ 0.99
Convertible Limited Partnership Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	2,228,404		2,200,907		2,233,088		2,325,220
Net income allocated to convertible limited partnership units	$ 600,000		$ 500,000		$ 2,200,000		$ 2,400,000
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	22,000		116,747		29,500		133,432

[1] Weighted average convertible limited partnership units of 2,228,404 and 2,233,088, which includes vested Series Z incentive units, for the three and nine months ended September 30, 2011, respectively, and weighted convertible limited partnership units of 2,200,907 and 2,325,220 which includes vested Series Z incentive units, for the three and nine months ended September 30, 2010, respectively, were not included in the determination of diluted EPS because they were anti-dilutive. The Company has the ability to redeem DownREIT limited partnership units for cash and does not consider them to be potentially dilutive securities. Stock options of 22,000 and 116,747 for the three months ended September 30, 2011 and 2010, respectively, and 29,500 and 133,432 for the nine months ended September 30, 2011 and 2010, respectively, were not included in the diluted earnings per share calculation because the exercise price of the options were greater than the average market price of the common shares for the three and six months ended and, therefore, were anti-dilutive.All shares of cumulative convertible preferred stock Series G have been excluded from diluted earnings per share for the three and nine months ended September 30, 2011 and 2010, as the effect was dilutive.

[2] Net income allocated to convertible limited partnership units, which includes vested Series Z units, aggregating $0.6 million and $0.5 million for the three months ended September 30, 2011 and 2010 respectively, and $2.2 million and $2.4 million for the nine months ended September 30, 2011 and 2010, respectively, have been excluded from income available to common stock holders for the calculation of net income per common share since these units are excluded from the diluted weighted average common shares for the period as the effect was anti-dilutive.