Investments in Joint Ventures - Condensed Combined Balance Sheets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule of Equity Method Investments [Line Items]
Less: Accumulated Depreciation	$ (732,635)	$ (658,729)
Net Investment in Real Estate	2,388,813	2,333,367
Total Assets	2,608,842	2,666,657
Indebtedness	1,338,175
Total Liabilities and Equity	2,608,842	2,666,657
Carrying Value of the Company's Investments in Joint Ventures	1,012	1,674
Corporate Joint Venture [Member]
Schedule of Equity Method Investments [Line Items]
Gross Investment in Real Estate	115,488	155,555
Less: Accumulated Depreciation	(38,535)	(41,342)
Net Investment in Real Estate	76,953	114,213
Other Assets	17,327	23,364
Total Assets	94,280	137,577
Indebtedness	81,764	112,261
Other Liabilities	4,817	5,779
Equity	7,699	19,537
Total Liabilities and Equity	94,280	137,577
Company's Share of Equity	1,252	3,029
Basis Differentials	(448)	(1,564)
Carrying Value of the Company's Investments in Joint Ventures	$ 804	$ 1,465