Mortgage Loans (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended
	Jun. 03, 2013 sqft	Sep. 30, 2013 sqft
Debt Instrument [Line Items]
Area of real estate property (in square feet)		640,000
PKY W. Rio Salado, LLC | US Airways Building
Debt Instrument [Line Items]
Area of real estate property (in square feet)	225,000	225,000
Mortgage secured for properties in a business acquisition	$ 3.5
Interest rate on mortgage (in percent)	3.00%
First termination option	Dec. 31, 2016