Derivatives and Hedging Activities (Narrative) (Details)	1 Months Ended		3 Months Ended		9 Months Ended
	Feb. 28, 2014 USD ($)	Jan. 31, 2014 USD ($)	Sep. 30, 2016 USD ($) swap_agreement	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)
Interest Rate Swap [Member]
Derivative [Line Items]
Amount of gain (loss) related to change in fair value and other ineffectiveness			$ 300,000	$ (900,000)	$ (1,100,000)	$ (1,500,000)
Fair value interest rate derivatives			(9,400,000)		(9,400,000)
Aggregate termination value had provisions been breached			(9,400,000)		(9,400,000)
Interest Rate Swap [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Reclassified from AOCI into interest expense			1,200,000		5,100,000
Gain in earnings related to ineffective portion			1,000,000		1,100,000
Loss on derivative instruments			(3,300,000)
Interest Rate Swap [Member] | Cash Flow Hedging [Member] | Interest Expense [Member]
Derivative [Line Items]
Derivative gain (loss) to be reclassified during next 12 months			$ (2,300,000)		(2,300,000)
Interest Rate Swap [Member] | Cash Flow Hedging [Member] | Credit Facility Term Loan [Member] | Line of Credit [Member]
Derivative [Line Items]
Number of interest rate swaps terminated | swap_agreement			2
Treasury Lock [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Loss on derivative instruments	$ (3,900,000)
Notional amount		$ 250,000,000
Term of derivative contract		10 years
Treasury Lock [Member] | Cash Flow Hedging [Member] | Interest Expense [Member]
Derivative [Line Items]
Interest expense			$ 100,000		$ 300,000