Derivatives and Hedging Activities (Narrative) (Details) - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended
	Feb. 28, 2014	Jan. 31, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
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		$ 400,000
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)			(1,400,000)	$ (17,500,000)	(2,100,000)	$ (10,400,000)
Fair value interest rate derivatives			17,200,000		17,200,000
Aggregate termination value had provisions been breached			17,200,000		17,200,000
Interest Rate Swap [Member] | Interest Expense [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative gain (loss) to be reclassified during next 12 months			$ 8,600,000		$ 8,600,000