Derivative Instruments (Details) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2014	Dec. 31, 2013
Interest Rate Derivatives [Abstract]
Number of interest rate swap contracts	3	3
aggregate notional amount	$ 104,500,000	$ 104,500,000	$ 105,200,000
Termination value of interest rate swap, including accrued interest	9,500,000	9,500,000
Interest Rate Cash Flow Hedges [Abstract]
Change in fair value of swaps as a decrease to other comprehensive income	1,500,000	2,400,000
Amount of loss reclassified into interest expense from AOCI	366,000	726,000
Ineffective portion of the change in the fair value of swaps as an adjustment to interest expense	37,000	55,000
Fair value of interest rate swaps	9,100,000	9,100,000	8,400,000
Amount estimated to be reclassified from accumulated other comprehensive income as an adjustment to interest expense	$ 1,400,000	$ 1,400,000