Real Estate Mortgages Receivable - Narrative (Details) (USD $)	1 Months Ended
	Jan. 31, 2013 property	Apr. 30, 2012	Sep. 30, 2014	Dec. 31, 2013
Real Estate Mortgages Receivable
Total real estate mortgage receivable included in other assets, carrying value			$ 8,100,000	$ 8,100,000
Mortgage financing related to sale of suburban property	7,700,000	400,000
Interest rate on real estate mortgage receivable	6.00%	6.00%
Number of properties sold or agreed to be sold	3
Number of buildings sold	18
Allowance for mortgage receivables			$ 0	$ 0