Earnings Per Common Share (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
Earnings Per Common Share
Net income (loss) 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
Basic weighted average common shares outstanding													36,442,782	35,827,167	33,663,589
Effect of potentially dilutive stock options, warrants and restricted stock awards													946,663	1,299,950	1,529,787
Diluted weighted average common shares outstanding													37,389,445	37,127,117	35,193,376
Earnings 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
Anti-dilutive shares excluded in the computation of diluted earnings per share													3,000,000	83,000	18,000