Derivative Instruments - Schedule of Gain or Loss Recognized on Interest Rate Derivatives Designated as Cash Flow Hedges (Details) - Cash flow hedging - Designated as hedging instrument - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in cumulative other comprehensive loss (effective portion)	$ 17	$ (114)	$ 84	$ (268)
Amount of loss reclassified from cumulative other comprehensive loss into interest expense (effective portion)	29	6	79	7
Amount of loss recognized in income (ineffective portion and amount excluded from effectiveness testing)	$ 293	$ 0	$ 293	$ 0