Derivative Instruments (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Interest rate contracts
Effects of derivative instruments
Amount of Loss (Gain) Recognized on Derivatives in the Statements of Income	$ (1,500)	$ 0	$ (500)
Cash Flow Hedging
Effects of derivative instruments
Amount of Loss (Gain) Recognized on Derivatives in the Statements of Income			(499)	$ 1,485
Cash Flow Hedging | Interest rate contracts | Interest expense Member
Effects of derivative instruments
Amount of Loss (Gain) Recognized on Derivatives in the Statements of Income			$ (499)	$ 1,485