Debt - Additional Information (Detail)	1 Months Ended		3 Months Ended		1 Months Ended				3 Months Ended
	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Sep. 30, 2012 USD ($)	Dec. 16, 2010 USD ($)	Sep. 22, 2006 Natural Alternatives International Europe Sa USD ($)	Sep. 22, 2006 Natural Alternatives International Europe Sa CHF	Feb. 19, 2007 Natural Alternatives International Europe Sa Amended Line of Credit Facility USD ($)	Feb. 19, 2007 Natural Alternatives International Europe Sa Amended Line of Credit Facility CHF	Sep. 30, 2012 Wells Fargo Foreign Exchange Facility	Sep. 30, 2012 Bank of America, N.A. Foreign Exchange Facility	Sep. 30, 2012 Minimum USD ($)	Sep. 30, 2012 Maximum USD ($)	Sep. 22, 2006 Maximum Natural Alternatives International Europe Sa
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity				$ 5,000,000
Commitment fee	12,500	12,500
Net income after taxes to maintain credit agreement eligibility											750,000
Ratio of total liabilities to tangible net worth												1.25
Principal amount that bears fluctuating rate of interest												100,000
Variable interest rate above LIBOR			2.75%
Fixed interest rate above LIBOR			2.50%
Line of credit facility full payment period			Nov. 01, 2013
Outstanding balance to maintain under line of credit for period of at least 30 consecutive days			0
Period to maintain zero balance under line of credit											30 days
Prepayment amount of line of credit outstanding subject to fixed interest rate			100,000
Foreign exchange facility, expiration date									Nov. 01, 2013	Mar. 15, 2013
Maximum aggregate amount outstanding at any one time under credit facility					1,400,000	1,300,000	532,000	500,000
Annual reduction of maximum amount outstanding under the credit facility					170,000	160,000
Line of credit facility, drawing term													24 months
Current account loans interest rate					5.00%	5.00%
Pre-payment penalty on fixed loan					0.10%	0.10%
Debt pre-payment penalty					1,064	1,000
Outstanding amount available under credit facilities			$ 5,500,000