Derivatives and Hedging Activities Accumulated Other Comprehensive Income Related to Derivatives (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative [Line Items]
Accumulated other comprehensive income on cash flow hedges, balance at beginning of period	$ (429)	$ (2,109)	$ (605)	$ (1,123)
Net change in unrealized gain/ (loss) on cash flow hedges	242	628	418	(358)
Accumulated other comprehensive income on cash flow hedges, balance at end of period	$ (187)	$ (1,481)	$ (187)	$ (1,481)