Note 6 - Interest Rate Swap Derivatives (Details Textual)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Interest Rate Swap [Member]
Derivative, Number of Instruments Held	3		3
Derivative, Notional Amount	$ 250,000,000		$ 250,000,000
Unrealized Gain (Loss) on Derivatives	$ (11,200,000)				$ (1,400,000)
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimate of Time to Transfer	1 year
Reclassification out of Accumulated Other Comprehensive Income [Member]
Interest Expense	$ 742,000
Derivative, Notional Amount	121,000,000	$ 48,600,000	121,000,000	$ 48,600,000
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net				0
Interest Expense	5,950,000	$ 4,873,000	11,167,000	$ 9,607,000
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred	3,100,000
Derivative, Net Liability Position, Aggregate Fair Value	11,200,000		11,200,000
Derivative Liability, Fair Value of Collateral	$ 11,700,000		$ 11,700,000