Other Assets (Details)	0 Months Ended
	Jun. 28, 2012 USD ($)	Jun. 28, 2012 GBP (£)	Sep. 30, 2012 USD ($)	Dec. 31, 2011 USD ($)
Other assets, details:
Straight-line rent assets, net of allowance of $32,940 and $34,457, respectively			$ 299,754,000	$ 266,620,000
Allowance on straight-line rent assets			32,940,000	34,457,000
Marketable debt securities			221,018,000
Leasing costs, net			93,619,000	92,288,000
Deferred financing costs, net			40,782,000	35,649,000
Goodwill			50,346,000	50,346,000
Marketable equity securities			22,769,000	17,053,000
Other			43,154,000	23,502,000
Total other assets			771,442,000	485,458,000
Adjusted cost basis of marketable equity securities			22,800,000	17,100,000
Additions related to accrued interest receivable			5,400,000	5,400,000
Interest rate on senior unsecured notes acquired (as a percent)	12.25%	12.25%
Yield to maturity (as a percent)	12.50%	12.50%
Marketable debt security, par value, discounted	214,900,000	136,800,000
Marketable debt security, par value		£ 138,500,000