Summary of Discontinued Operations (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rental revenues	$ 122,711	$ 106,342
Other Real Estate Revenue	10,479	9,675
Total operating revenues	133,367	116,286
Operating Costs and Expenses	86,210	78,056
Interest expense	15,716	14,110
(Loss) income from discontinued operations before gain on sale	0	484
Net loss on insurance and other settlement proceeds on discontinued operations	0	(54)
Gain on sale of discontinued operations	0	9,429
Income from discontinued operations	0	9,859
Disposal Groups, Including Discontinued Operations, Name [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rental revenues	0	3,565
Other Real Estate Revenue	0	417
Total operating revenues	0	3,982
Operating Costs and Expenses	0	2,179
Depreciation	0	1,060
Interest expense	0	259
Total expense	$ 0	$ 3,498