Accounting Policies (Business Combinations) (Details) (USD $) In Millions, unless otherwise specified			12 Months Ended
Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Building
Business Combinations
Estimated remaining life (in years)			35 years
Net Real Estate Assets having a Tenant Purchase Option Liability	$ 386.4	$ 432.5

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

No definition available.

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration