Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Fair Value Asset And Liabilities Measured On Recurring Basis [Line Items]
Total assets at fair value	$ 19,985	$ 159,322
Total liabilities at fair value	(1,801)	(761)
Impairment charges on real estate	900	3,008
Level 1 [Member]
Fair Value Asset And Liabilities Measured On Recurring Basis [Line Items]
Total assets at fair value	15,445	122,167
Level 2 [Member]
Fair Value Asset And Liabilities Measured On Recurring Basis [Line Items]
Total assets at fair value	4,540	37,155
Total liabilities at fair value	(1,801)	(761)
Derivative Instruments - Liabilities [Member]
Fair Value Asset And Liabilities Measured On Recurring Basis [Line Items]
Total liabilities at fair value	(1,801)	(761)
Derivative Instruments - Liabilities [Member] | Level 2 [Member]
Fair Value Asset And Liabilities Measured On Recurring Basis [Line Items]
Total liabilities at fair value	(1,801)	(761)
Money Market Funds [Member]
Fair Value Asset And Liabilities Measured On Recurring Basis [Line Items]
Total assets at fair value	15,275	121,943
Money Market Funds [Member] | Level 1 [Member]
Fair Value Asset And Liabilities Measured On Recurring Basis [Line Items]
Total assets at fair value	15,275	121,943
Certificates Of Deposit [Member]
Fair Value Asset And Liabilities Measured On Recurring Basis [Line Items]
Total assets at fair value	3,555	36,268
Certificates Of Deposit [Member] | Level 2 [Member]
Fair Value Asset And Liabilities Measured On Recurring Basis [Line Items]
Total assets at fair value	3,555	36,268
Stock [Member]
Fair Value Asset And Liabilities Measured On Recurring Basis [Line Items]
Total assets at fair value	170	224
Stock [Member] | Level 1 [Member]
Fair Value Asset And Liabilities Measured On Recurring Basis [Line Items]
Total assets at fair value	170	224
Derivative Instruments - Assets [Member]
Fair Value Asset And Liabilities Measured On Recurring Basis [Line Items]
Total assets at fair value	985	887
Derivative Instruments - Assets [Member] | Level 2 [Member]
Fair Value Asset And Liabilities Measured On Recurring Basis [Line Items]
Total assets at fair value	$ 985	$ 887