Investments in Unconsolidated Real Estate Entities - Schedule of Operation for Apartment LLCs (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Revenues
Rental	$ 85,042	$ 77,081	$ 167,438	$ 152,736
Other property revenues	5,213	4,873	10,132	9,272
Total revenues	90,484	82,160	178,013	162,436
Expenses
Property operating and maintenance	38,671	35,231	76,426	69,868
Interest	11,130	11,103	22,272	22,748
Total expenses	65,294	59,239	129,209	118,288
Net income available to the Company	27,488	21,079	47,829	42,879
Company's share of net income in Apartment LLCs	477	495	955	6,941
Unconsolidated Properties [Member]
Revenues
Rental	6,350	6,152	12,635	12,194
Other property revenues	515	501	961	937
Total revenues	6,865	6,653	13,596	13,131
Expenses
Property operating and maintenance	2,738	2,555	5,389	5,082
Depreciation and amortization	1,350	1,428	2,690	3,033
Interest	2,258	2,258	4,496	4,625
Total expenses	6,346	6,241	12,575	12,740
Net loss from continuing operations	519	412	1,021	391
Gain from discontinued operations				21,607
Net income available to the Company	519	412	1,021	21,998
Company's share of net income in Apartment LLCs	$ 477	$ 495	$ 955	$ 6,941