Quarterly Financial Information (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended												12 Months Ended
	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	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, 2014	Jun. 30, 2013	Jun. 30, 2012
Quarterly Financial Information (Unaudited)
Net sales	$ 80,619	$ 79,997	$ 67,326	$ 45,829	$ 40,174	$ 39,022	$ 36,564	$ 35,294	$ 35,690	$ 30,688	$ 27,734	$ 28,878	$ 273,771	$ 151,054	$ 122,990
Cost of sales	24,691	23,865	26,284	44,523	24,971	23,852	23,143	21,668	23,677	19,797	20,307	20,262	99,263	93,634	84,043
Gross profit	55,928	56,132	41,042	1,306	15,203	15,170	13,421	13,626	12,013	10,891	7,427	8,616	154,408	57,420	38,947
Operating expenses	18,577	20,143	15,675	11,924	9,527	10,474	8,727	9,935	9,407	8,527	6,932	7,171	66,319	38,663	32,037
Operating income	37,351	35,989	25,367	(10,618)	5,676	4,696	4,694	3,691	2,606	2,364	495	1,445	88,089	18,757	6,910
Other income	220	297	1,025	389	(109)	594	(86)	1,529	(362)	427	654	(1,011)	1,931	1,928	(292)
Income tax expense (benefit)	14,019	13,280	9,800	(4,242)	1,950	1,327	1,749	2,277	812	1,057	519	212	32,857	7,303	2,600
Less: Net income (loss) attributable to noncontrolling interest	17	11	26	8	54	16	(22)	17	17	16	21	16	62	65	70
Net income attributable to Lannett Company, Inc.	$ 23,535	$ 22,995	$ 16,566	$ (5,995)	$ 3,563	$ 3,947	$ 2,881	$ 206	$ 1,415	$ 1,718	$ 609	$ 206	$ 57,101	$ 13,317	$ 3,948
Earnings (loss) per common share attributable to Lannett Company Inc
Basic (in dollars per share)	$ 0.66	$ 0.66	$ 0.48	$ (0.20)	$ 0.12	$ 0.14	$ 0.10	$ 0.10	$ 0.05	$ 0.06	$ 0.02	$ 0.01	$ 1.70	$ 0.47	$ 0.14
Diluted (in dollars per share)	$ 0.64	$ 0.63	$ 0.46	$ (0.20)	$ 0.12	$ 0.14	$ 0.10	$ 0.10	$ 0.05	$ 0.06	$ 0.02	$ 0.01	$ 1.62	$ 0.46	$ 0.14