Derivative Instruments - Schedule of derivative financial instruments at fair value (Details) (Interest rate swap, Designated as hedging instrument, Accounts payable and accrued expenses, USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Interest rate swap | Designated as hedging instrument | Accounts payable and accrued expenses
Derivatives, Fair Value [Line Items]
Pay-fixed swaps	$ 8,274	$ 11,705