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	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Amount of loss recognized in cumulative other comprehensive loss (effective portion)	$ (297)	$ (554)	$ (1,149)
Amount of loss reclassified from cumulative other comprehensive loss into interest expense (effective portion)	49	3,792	4,924
Amount of loss recognized in income (ineffective portion and amount excluded from effectiveness testing)	$ 0	$ 241	$ 0