Derivative Instruments and Hedging Activities Effect of Derivative Financial Instruments on the Statements of Income and Comprehensive Income (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain/(loss) recognized in OCI on derivative			$ 194,000	$ (1,439,000)
Amount of loss reclassified from accumulated OCI into interest expense			(681,000)	(693,000)
Amount of gain/(loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)			$ 0	$ 0
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain/(loss) recognized in OCI on derivative	$ 670,000	$ (1,032,000)
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of loss reclassified from accumulated OCI into interest expense	(341,000)	(349,000)
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Other Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain/(loss) recognized in income on derivative (ineffective portion and amount excluded from effectiveness testing)	$ 0	$ 0