Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2014
Interim Financial Information
Net sales	$ 168,887	$ 163,712	$ 127,059	$ 106,433									$ 566,091	$ 406,837	$ 273,771
Settlement agreement		(23,598)											(23,598)
Total net sales	168,887	140,114	127,059	106,433	$ 99,276	$ 99,352	$ 114,822	$ 93,387	$ 80,619	$ 79,997	$ 67,326	$ 45,829	542,493	406,837	273,771
Cost of sales	88,957	82,623	55,414	29,006	27,326	23,714	27,621	21,820	24,691	23,865	26,284	44,523	237,371	100,344	97,839
Gross profit	79,930	57,491	71,645	77,427	71,950	75,638	87,201	71,567	55,928	56,132	41,042	1,306	286,493	306,356	154,408
Operating expenses	49,535	38,874	41,320	26,006	20,932	21,363	20,658	16,916	18,577	20,143	15,675	11,924	155,735	79,869	66,319
Operating income	30,395	18,617	30,325	51,421	51,018	54,275	66,543	54,651	37,351	35,989	25,367	(10,618)	130,758	226,487	88,089
Other income (loss)	(29,752)	(26,830)	(10,827)	(1,170)	165	(42)	713	99	220	297	1,025	389	(68,579)	935	1,931
Income tax expense (benefit)	(2,948)	(2,743)	5,958	17,055	17,222	17,973	22,435	19,800	14,019	13,280	9,800	(4,242)	17,322	77,430	32,857
Less: Net income attributable to noncontrolling interest	20	20	20	15	18	27	10	18	17	11	26	8	75	73	62
Net income attributable to Lannett Company, Inc.	$ 3,571	$ (5,490)	$ 13,520	$ 33,181	$ 33,943	$ 36,233	$ 44,811	$ 34,932	$ 23,535	$ 22,995	$ 16,566	$ (5,995)	$ 44,782	$ 149,919	$ 57,101
Loss per common share attributable to Lannett Company, Inc.:
Basic (in dollars per share)	$ 0.10	$ (0.15)	$ 0.37	$ 0.91	$ 0.94	$ 1.01	$ 1.26	$ 0.98	$ 0.66	$ 0.66	$ 0.48	$ (0.20)	$ 1.23	$ 4.18	$ 1.70
Diluted (in dollars per share)	$ 0.10	$ (0.15)	$ 0.36	$ 0.89	$ 0.91	$ 0.97	$ 1.21	$ 0.94	$ 0.64	$ 0.63	$ 0.46	$ (0.20)	$ 1.20	$ 4.04	$ 1.62