| Segment Reporting Disclosure [Text Block] |
Reportable Segments Operating segments are defined as components of an enterprise that engage in business activities from which they may earn revenues and incur expenses and about which discrete financial information is available that is evaluated regularly by the chief operating decision maker. The chief operating decision maker decides how resources are allocated and assesses performance on a recurring basis at least quarterly. The Company's primary business is the acquisition, development and management of multifamily residential properties, which includes the generation of rental and other related income through the leasing of apartment units to residents. The chief operating decision maker evaluates the Company's operating performance geographically by market and both on a same store and non-same store basis. The Company's operating segments (geographic markets) have been aggregated into four reportable segments based upon the geographic region in which they are located. The Company's fee and asset management and development (including its partially owned properties) activities are other business activities that do not constitute an operating segment and as such, have been aggregated in the "Other" category in the tables presented below. All revenues are from external customers and there is no customer who contributed 10% or more of the Company’s total revenues during the three years ended December 31, 2012, 2011 or 2010. The primary financial measure for the Company's rental real estate segment is net operating income (“NOI”), which represents rental income less: 1) property and maintenance expense; 2) real estate taxes and insurance expense; and 3) property management expense (all as reflected in the accompanying consolidated statements of operations). The Company believes that NOI is helpful to investors as a supplemental measure of its operating performance because it is a direct measure of the actual operating results of the Company's apartment communities. Current year NOI is compared to prior year NOI and current year budgeted NOI as a measure of financial performance. The following tables present NOI for each segment from our rental real estate specific to continuing operations for the years ended December 31, 2012, 2011 and 2010, respectively, as well as total assets and capital expenditures at December 31, 2012 and 2011, respectively (amounts in thousands):
| | | | | | | | | | | | | | | | | | | | | | | | | | Year Ended December 31, 2012 | | Northeast | | Northwest | | Southeast | | Southwest | | Other (3) | | Total | Rental income: | | | | | | | | | | | | Same store (1) | $ | 708,009 |
| | $ | 386,813 |
| | $ | 332,185 |
| | $ | 441,911 |
| | $ | — |
| | $ | 1,868,918 |
| Non-same store/other (2) (3) | 110,060 |
| | 54,414 |
| | 19,853 |
| | 60,962 |
| | (65 | ) | | 245,224 |
| Properties sold – March YTD 2013 (4) | — |
| | — |
| | — |
| | — |
| | (243,833 | ) | | (243,833 | ) | Total rental income | 818,069 |
| | 441,227 |
| | 352,038 |
| | 502,873 |
| | (243,898 | ) | | 1,870,309 |
| Operating expenses: | | | | | | | | | | | | Same store (1) | 251,538 |
| | 127,213 |
| | 127,279 |
| | 143,884 |
| | — |
| | 649,914 |
| Non-same store/other (2) (3) | 33,423 |
| | 24,755 |
| | 7,550 |
| | 20,837 |
| | 3,285 |
| | 89,850 |
| Properties sold – March YTD 2013 (4) | — |
| | — |
| | — |
| | — |
| | (72,109 | ) | | (72,109 | ) | Total operating expenses | 284,961 |
| | 151,968 |
| | 134,829 |
| | 164,721 |
| | (68,824 | ) | | 667,655 |
| NOI: | | | | | | | | | | | | Same store (1) | 456,471 |
| | 259,600 |
| | 204,906 |
| | 298,027 |
| | — |
| | 1,219,004 |
| Non-same store/other (2) (3) | 76,637 |
| | 29,659 |
| | 12,303 |
| | 40,125 |
| | (3,350 | ) | | 155,374 |
| Properties sold – March YTD 2013 (4) | — |
| | — |
| | — |
| | — |
| | (171,724 | ) | | (171,724 | ) | Total NOI | $ | 533,108 |
| | $ | 289,259 |
| | $ | 217,209 |
| | $ | 338,152 |
| | $ | (175,074 | ) | | $ | 1,202,654 |
| | | | | | | | | | | | | Total assets | $ | 6,972,992 |
| | $ | 2,953,700 |
| | $ | 2,268,805 |
| | $ | 3,191,403 |
| | $ | 1,814,100 |
| | $ | 17,201,000 |
| | | | | | | | | | | | | Capital expenditures | $ | 58,298 |
| | $ | 35,650 |
| | $ | 27,521 |
| | $ | 28,505 |
| | $ | 2,854 |
| | $ | 152,828 |
|
| | (1) | Same store primarily includes all properties acquired or completed and stabilized prior to January 1, 2011, less properties subsequently sold, which represented 98,577 apartment units. |
| | (2) | Non-same store primarily includes properties acquired after January 1, 2011, plus any properties in lease-up and not stabilized as of January 1, 2011. |
| | (3) | Other includes development and other corporate operations. |
| | (4) | Properties sold – March YTD 2013 reflects discontinued operations for properties sold during the first three months of 2013. |
| | | | | | | | | | | | | | | | | | | | | | | | | | Year Ended December 31, 2011 | | Northeast | | Northwest | | Southeast | | Southwest | | Other (3) | | Total | Rental income: | | | | | | | | | | | | Same store (1) | $ | 671,633 |
| | $ | 356,822 |
| | $ | 317,205 |
| | $ | 425,789 |
| | $ | — |
| | $ | 1,771,449 |
| Non-same store/other (2) (3) | 51,566 |
| | 9,900 |
| | 14,488 |
| | 30,539 |
| | (3,477 | ) | | 103,016 |
| Properties sold – March YTD 2013 (4) | — |
| | — |
| | — |
| | — |
| | (229,823 | ) | | (229,823 | ) | Total rental income | 723,199 |
| | 366,722 |
| | 331,693 |
| | 456,328 |
| | (233,300 | ) | | 1,644,642 |
| Operating expenses: | | | | | | | | | | | | Same store (1) | 245,166 |
| | 125,008 |
| | 123,720 |
| | 144,777 |
| | — |
| | 638,671 |
| Non-same store/other (2) (3) | 14,101 |
| | 3,946 |
| | 5,165 |
| | 12,144 |
| | 7,326 |
| | 42,682 |
| Properties sold – March YTD 2013 (4) | — |
| | — |
| | — |
| | — |
| | (71,233 | ) | | (71,233 | ) | Total operating expenses | 259,267 |
| | 128,954 |
| | 128,885 |
| | 156,921 |
| | (63,907 | ) | | 610,120 |
| NOI: | | | | | | | | | | | | Same store (1) | 426,467 |
| | 231,814 |
| | 193,485 |
| | 281,012 |
| | — |
| | 1,132,778 |
| Non-same store/other (2) (3) | 37,465 |
| | 5,954 |
| | 9,323 |
| | 18,395 |
| | (10,803 | ) | | 60,334 |
| Properties sold – March YTD 2013 (4) | — |
| | — |
| | — |
| | — |
| | (158,590 | ) | | (158,590 | ) | Total NOI | $ | 463,932 |
| | $ | 237,768 |
| | $ | 202,808 |
| | $ | 299,407 |
| | $ | (169,393 | ) | | $ | 1,034,522 |
| | | | | | | | | | | | | Total assets | $ | 6,550,979 |
| | $ | 2,816,078 |
| | $ | 2,340,902 |
| | $ | 3,238,164 |
| | $ | 1,713,180 |
| | $ | 16,659,303 |
| | | | | | | | | | | | | Capital expenditures | $ | 51,203 |
| | $ | 32,522 |
| | $ | 24,813 |
| | $ | 27,792 |
| | $ | 8,122 |
| | $ | 144,452 |
|
| | (1) | Same store primarily includes all properties acquired or completed and stabilized prior to January 1, 2011, less properties subsequently sold, which represented 98,577 apartment units. |
| | (2) | Non-same store primarily includes properties acquired after January 1, 2011, plus any properties in lease-up and not stabilized as of January 1, 2011. |
| | (3) | Other includes development, condominium conversion overhead of $0.4 million and other corporate operations. |
| | (4) | Properties sold – March YTD 2013 reflects discontinued operations for properties sold during the first three months of 2013. |
| | | | | | | | | | | | | | | | | | | | | | | | | | Year Ended December 31, 2010 | | Northeast | | Northwest | | Southeast | | Southwest | | Other (3) | | Total | Rental income: | | | | | | | | | | | | Same store (1) | $ | 553,561 |
| | $ | 322,427 |
| | $ | 342,080 |
| | $ | 412,414 |
| | $ | — |
| | $ | 1,630,482 |
| Non-same store/other (2) (3) | 95,493 |
| | 18,825 |
| | 9,009 |
| | 13,587 |
| | (3,604 | ) | | 133,310 |
| Properties sold in 2012 (4) | — |
| | — |
| | — |
| | — |
| | (98,559 | ) | | (98,559 | ) | Properties sold – March YTD 2013 (5) | — |
| | — |
| | — |
| | — |
| | (218,452 | ) | | (218,452 | ) | Total rental income | 649,054 |
| | 341,252 |
| | 351,089 |
| | 426,001 |
| | (320,615 | ) | | 1,446,781 |
| Operating expenses: | | | | | | | | | | | | Same store (1) | 207,131 |
| | 119,797 |
| | 139,550 |
| | 147,732 |
| | — |
| | 614,210 |
| Non-same store/other (2) (3) | 48,119 |
| | 8,300 |
| | 3,729 |
| | 7,198 |
| | 12,230 |
| | 79,576 |
| Properties sold in 2012 (4) | — |
| | — |
| | — |
| | — |
| | (39,015 | ) | | (39,015 | ) | Properties sold – March YTD 2013 (5) | — |
| | — |
| | — |
| | — |
| | (78,640 | ) | | (78,640 | ) | Total operating expenses | 255,250 |
| | 128,097 |
| | 143,279 |
| | 154,930 |
| | (105,425 | ) | | 576,131 |
| NOI: | | | | | | | | | | | | Same store (1) | 346,430 |
| | 202,630 |
| | 202,530 |
| | 264,682 |
| | — |
| | 1,016,272 |
| Non-same store/other (2) (3) | 47,374 |
| | 10,525 |
| | 5,280 |
| | 6,389 |
| | (15,834 | ) | | 53,734 |
| Properties sold in 2012 (4) | — |
| | — |
| | — |
| | — |
| | (59,544 | ) | | (59,544 | ) | Properties sold – March YTD 2013 (5) | — |
| | — |
| | — |
| | — |
| | (139,812 | ) | | (139,812 | ) | Total NOI | $ | 393,804 |
| | $ | 213,155 |
| | $ | 207,810 |
| | $ | 271,071 |
| | $ | (215,190 | ) | | $ | 870,650 |
|
| | (1) | Same store primarily includes all properties acquired or completed and stabilized prior to January 1, 2010, less properties subsequently sold, which represented 101,312 apartment units. |
| | (2) | Non-same store primarily includes properties acquired after January 1, 2010, plus any properties in lease-up and not stabilized as of January 1, 2010. |
| | (3) | Other includes development, condominium conversion overhead of $0.6 million and other corporate operations. |
| | (4) | Reflects discontinued operations for properties sold during 2012. |
| | (5) | Properties sold – March YTD 2013 reflects discontinued operations for properties sold during the first three months of 2013. |
Note: Markets included in the above geographic segments are as follows: (a) Northeast – New England (excluding Boston), Boston, New York Metro, DC Northern Virginia and Suburban Maryland. (b) Northwest – Denver, San Francisco Bay Area and Seattle/Tacoma. (c) Southeast – Atlanta, Jacksonville, Orlando and South Florida. (d) Southwest – Inland Empire, Los Angeles, Orange County, Phoenix and San Diego.
The following table presents a reconciliation of NOI from our rental real estate specific to continuing operations for the years ended December 31, 2012, 2011 and 2010, respectively (amounts in thousands):
| | | | | | | | | | | | | | Year Ended December 31, | | 2012 | | 2011 | | 2010 | Rental income | $ | 1,870,309 |
| | $ | 1,644,642 |
| | $ | 1,446,781 |
| Property and maintenance expense | (365,778 | ) | | (337,419 | ) | | (323,743 | ) | Real estate taxes and insurance expense | (219,975 | ) | | (190,834 | ) | | (172,531 | ) | Property management expense | (81,902 | ) | | (81,867 | ) | | (79,857 | ) | Total operating expenses | (667,655 | ) | | (610,120 | ) | | (576,131 | ) | Net operating income | $ | 1,202,654 |
| | $ | 1,034,522 |
| | $ | 870,650 |
|
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