Note 6 - Stock-based Compensation - Stock Option Activity (Details) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2016 USD ($) $ / shares shares
Options outstanding, beginning balance (in shares) | shares	371
Exercise price per share, beginning balance (in dollars per share)	$ 20.81
Aggregate intrinsic value, beginning balance | $
Options outstanding, exercised (in shares) | shares	(22)
Exercise price per share, exercised (in dollars per share)	$ 18.74
Aggregate intrinsic value, exercised | $	$ 368
Options outstanding, ending balance (in shares) | shares	349
Exercise price per share, ending balance (in dollars per share)	$ 20.94
Contractual term - weighted average, ending balance (Year)	7 years 284 days
Aggregate intrinsic value, ending balance | $	$ 5,128
Options outstanding, vested and anticipated to vest in the future (in shares) | shares	343
Weighted average, vested and anticipated to vest in future (in dollars per share)	$ 20.91
Contractual term - weighted average, vested and anticipated to vest in future (Year)	7 years 277 days
Aggregate intrinsic value, vested and anticipated to vest in future | $	$ 5,057
Options outstanding, exercisable (in shares) | shares	120
Weighted average, exercisable (in dollars per share)	$ 15.98
Contractual term - weighted average, exercisable (Year)	6 years 69 days
Aggregate intrinsic value, exercisable | $	$ 2,369
Minimum [Member]
Exercise price per share, beginning balance (in dollars per share)	$ 9.16
Exercise price per share, exercised (in dollars per share)	13.06
Exercise price per share, ending balance (in dollars per share)	9.16
Maximum [Member]
Exercise price per share, beginning balance (in dollars per share)	34.49
Exercise price per share, exercised (in dollars per share)	20.50
Exercise price per share, ending balance (in dollars per share)	$ 34.49