Derivatives and Hedging Activities (Details)	9 Months Ended
	Sep. 30, 2017 USD ($) Financial_Instrument	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Derivative [Line Items]
Expected amount of derivative related interest to be reclassified to interest expense over the next 12 months	$ 297,000
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Other Assets [Member]
Derivative [Line Items]
Derivative asset	510,000		$ 44,000
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Accounts Payable And Other Liabilities [Member]
Derivative [Line Items]
Derivative liability	0		$ (1,077,000)
Interest Rate Swap [Member] | Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount	$ 505,000,000
Number of derivative instruments held | Financial_Instrument	10
Interest Rate Swap [Member] | Cash Flow Hedging [Member] | Designated as Hedging Instrument [Member] | Interest Expense [Member]
Derivative [Line Items]
Amount of income (loss) recognized in OCI on derivatives (effective portion)	$ 581,000	$ (6,035,000)
Amount of loss reclassified from accumulated OCI into income (effective portion)	$ 962,000	$ 3,091,000