Note 3 - Earnings Per Share - Basic and Diluted Earnings Per Share (Details) (USD $)	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Net income attributable to Natural Grocers by Vitamin Cottage, Inc.	$ 13,473,000	$ 10,552,000	$ 6,649,000
Basic (in shares)	22,466,432	22,399,346	22,372,184
Effect of dilutive securities (in shares)	13,403	42,036	90,909
Weighted average common shares outstanding including effect of dilutive securities (in shares)	22,479,835	22,441,382	22,463,093
Basic earnings per share (in dollars per share)	$ 0.60	$ 0.47	$ 0.30
Diluted earnings per share (in dollars per share)	$ 0.60	$ 0.47	$ 0.30