Real Estate and Accumulated Depreciation (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of accumulated depreciation per Schedule III to Consolidated Balance Sheets
Total accumulated depreciation per Schedule III	$ 2,150,713
Accumulated depreciation on other investments	7,194
Total per consolidated balance sheet	$ 2,157,907	$ 1,595,678