Quarterly Financial Information (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended												12 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2011
Quarterly Financial Information (Unaudited)
Net sales	$ 40,174	$ 39,022	$ 36,564	$ 35,294	$ 35,690	$ 30,688	$ 27,734	$ 28,878	$ 25,507	$ 25,893	$ 30,039	$ 25,396	$ 151,054	$ 122,990	$ 106,835
Cost of sales	24,971	23,852	23,143	21,668	23,677	19,797	20,307	20,262	21,752	20,589	21,682	19,492	93,634	84,043	83,515
Gross profit	15,203	15,170	13,421	13,626	12,013	10,891	7,427	8,616	3,755	5,304	8,357	5,904	57,420	38,947	23,320
Operating expenses	9,527	10,474	8,727	9,935	9,407	8,527	6,932	7,171	7,186	6,134	4,536	6,643	38,663	32,037	24,499
Operating income (loss)	5,676	4,696	4,694	3,691	2,606	2,364	495	1,445	(3,431)	(830)	3,821	(739)	18,757	6,910	(1,179)
Other income (expense)	(109)	594	(86)	1,529	(362)	427	654	(1,011)	568	22	(67)	(45)	1,928	(292)	478
Income tax expense (benefit)	1,950	1,327	1,749	2,277	812	1,057	519	212	(1,015)	(450)	1,394	(390)	7,303	2,600	(461)
Less: Net income attributable to noncontrolling interest	54	16	(22)	17	17	16	21	16	16	4	7	10	65	70	37
Net income (loss) attributable to Lannett Company, Inc.	$ 3,563	$ 3,947	$ 2,881	$ 2,926	$ 1,415	$ 1,718	$ 609	$ 206	$ (1,864)	$ (362)	$ 2,353	$ (404)	$ 13,317	$ 3,948	$ (277)
Earnings per common share
Basic (in dollars per share)	$ 0.12	$ 0.14	$ 0.10	$ 0.10	$ 0.05	$ 0.06	$ 0.02	$ 0.01	$ (0.07)	$ (0.01)	$ 0.09	$ (0.02)	$ 0.47	$ 0.14	$ (0.01)
Diluted (in dollars per share)	$ 0.12	$ 0.14	$ 0.10	$ 0.10	$ 0.05	$ 0.06	$ 0.02	$ 0.01	$ (0.07)	$ (0.01)	$ 0.09	$ (0.02)	$ 0.46	$ 0.14	$ (0.01)