Derivatives and Hedging Activities (Details)	6 Months Ended
	Jun. 30, 2015 USD ($) Financial_Instrument	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Derivative [Line Items]
Expected amount of derivative related interest to be reclassified to interest expense over the next 12 months	$ 4,389,000
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Other Assets [Member]
Derivative [Line Items]
Derivative asset			$ 1,153,000
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Accounts Payable And Other Liabilities [Member]
Derivative [Line Items]
Derivative liability	(2,226,000)		$ (749,000)
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Notional amount	$ 505,000,000
Number of derivative instruments held | Financial_Instrument	10
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Interest Expense [Member]
Derivative [Line Items]
Amount of gain (loss) recognized in OCI on derivatives (effective portion)	$ (5,374,000)	$ (7,186,000)
Amount of loss reclassified from accumulated OCI into income (effective portion)	$ 2,744,000	$ 2,681,000