Derivatives and Hedging Activities (Narrative) (Details) - USD ($)	1 Months Ended		3 Months Ended		6 Months Ended
	Feb. 28, 2014	Jan. 31, 2014	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Interest Rate Swap [Member]
Derivative [Line Items]
Amount of gain (loss) recognized in income on derivative (ineffective portion, reclassifications of missed forecasted transactions and amounts excluded from effectiveness testing)			$ (200,000)	$ 300,000	$ (1,300,000)	$ (700,000)
Fair value interest rate derivatives			16,600,000		16,600,000
Aggregate termination value had provisions been breached			16,600,000		16,600,000
Interest Rate Swap [Member] | Interest Expense [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative gain (loss) to be reclassified during next 12 months			6,700,000		6,700,000
Treasury Lock [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative, notional amount		$ 250,000,000
Term of derivative contract		10 years
Loss from settlement of derivative	$ 3,900,000
Treasury Lock [Member] | Interest Expense [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Interest expense			$ 100,000		$ 200,000