Note 8 - Income Taxes (Details Textual) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Income Tax Expense (Benefit)	$ 12,584,000	$ 6,992,000	$ 20,163,000	$ 8,539,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	2,400,000		2,400,000		$ 2,400,000
Unrecognized Tax Benefits, Income Tax Penalties Accrued	0		0		0
Unrecognized Tax Benefits, Interest on Income Taxes Expense			145,000		$ 145,000
Accounting Standards Update 2016-09 [Member]
Income Tax Expense (Benefit)	$ (900,000)		$ (2,000,000)
Domestic Tax Authority [Member] | Latest Tax Year [Member]
Open Tax Year			2016
Domestic Tax Authority [Member] | Earliest Tax Year [Member]
Open Tax Year			2013
State and Local Jurisdiction [Member] | Latest Tax Year [Member]
Open Tax Year			2016
State and Local Jurisdiction [Member] | Earliest Tax Year [Member]
Open Tax Year			2012