Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate agreements	$ 2,537		$ 691
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	139,690	[1]	56,718	[1]
Tenant receivables, net	129,523	[1]	134,006	[1]
Accounts payable	14,637	[1]	15,763	[1]
Line of credit and notes payable	1,472,525		1,402,525
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	139,690	[1]	56,718	[1]
Tenant receivables, net	129,523	[1]	134,006	[1]
Accounts payable	14,637	[1]	15,763	[1]
Line of credit and notes payable	1,529,811		1,428,255
Interest Rate Swap [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate agreements	2,537		691
Interest Rate Swap [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate agreements	2,537		691
Interest Rate Cap [Member] | Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate agreements	0
Interest Rate Cap [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate agreements	$ 0

[1] For the periods presented, the carrying value approximates estimated fair value.