Derivative Instruments (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Interest Rate Derivatives [Abstract]
Number of interest rate swap contracts	3		3
aggregate notional amount	$ 102,600		$ 102,600		$ 103,600
Termination value of interest rate swap, including accrued interest	8,000		8,000
Interest Rate Cash Flow Hedges [Abstract]
Fair value of interest rate swaps	7,900		7,900		$ 8,500
Amount estimated to be reclassified from accumulated other comprehensive income as an increase to interest expense	1,200		1,200
Interest Rate Swap [Member] | Other Comprehensive Income (Loss) [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) related to the effective portion recognized in other comprehensive income (loss)	277	$ (1,511)	(1,022)	$ (2,382)
Interest Rate Swap [Member] | Interest Expense [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) related to the effective portion subsequently reclassified to earnings	(351)	(366)	(703)	(726)
Amount of gain (loss) related to the ineffective portion	$ (2)	$ (37)	$ (62)	$ (55)