Intangible Assets and Liabilities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Y	Dec. 31, 2010
Schedule of finite lived intangible assets and liabilities
Finite Lived Intangible Assets and Liabilities	$ 94.9	$ 124.4
Finite Lived Intangible Assets and Liabilities Accumulated Amortization	21.3	56.2
Finite Lived Intangible Assets and Liabilities Weighted Average Useful Life	17.3
Other Assets [Member] | Goodwill [Member]
Schedule of finite lived intangible assets and liabilities
Assets Gross Balance at December 31,	3.5	3.5
Assets Accumulated Amortization Balance at December 31,	0	0
Other Assets [Member] | Deferred Financing Costs [Member]
Schedule of finite lived intangible assets and liabilities
Assets Gross Balance at December 31,	17.6	20.7
Assets Accumulated Amortization Balance at December 31,	3.8	8.7
Assets, Weighted Avg. life (Years)	5.1
Other Assets [Member] | Customer Relationships [Member]
Schedule of finite lived intangible assets and liabilities
Assets Gross Balance at December 31,	2.6	1.4
Assets Accumulated Amortization Balance at December 31,	0.5	0.2
Assets, Weighted Avg. life (Years)	31.6
Real estate properties [Member] | At-market lease intangibles [Member]
Schedule of finite lived intangible assets and liabilities
Assets Gross Balance at December 31,	63.3	93.0
Assets Accumulated Amortization Balance at December 31,	16.9	49.0
Assets, Weighted Avg. life (Years)	7.3
Below-market lease intangibles [Member] | Other Liabilities [Member]
Schedule of finite lived intangible assets and liabilities
Liabilities Gross Balance at December 31,	(6.9)	(8.8)
Liabilities Accumulated Amortization Balance at December 31,	(1.4)	(2.9)
Liabilities, Weighted Avg. life (Years)	15.0
Above-market lease intangibles [Member] | Other Assets [Member]
Schedule of finite lived intangible assets and liabilities
Assets Gross Balance at December 31,	14.8	14.6
Assets Accumulated Amortization Balance at December 31,	$ 1.5	$ 1.2
Assets, Weighted Avg. life (Years)	57.2