Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	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, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Common Share
Net Income Attributable to Lannett Company, Inc	$ 33,943	$ 36,233	$ 44,811	$ 34,932	$ 23,535	$ 22,995	$ 16,566	$ (5,995)	$ 3,563	$ 3,947	$ 2,881	$ 2,926	$ 149,919	$ 57,101	$ 13,317
Basic weighted average common shares outstanding													35,827,167	33,663,589	28,467,598
Effect of potentially dilutive stock options and restricted stock awards													1,299,950	1,529,787	475,335
Diluted weighted average common shares outstanding													37,127,117	35,193,376	28,942,933
Earnings per common share attributable to Lannett Company, Inc.:
Basic (in dollars per share)	$ 0.94	$ 1.01	$ 1.26	$ 0.98	$ 0.66	$ 0.66	$ 0.48	$ (0.20)	$ 0.12	$ 0.14	$ 0.10	$ 0.10	$ 4.18	$ 1.70	$ 0.47
Diluted (in dollars per share)	$ 0.91	$ 0.97	$ 1.21	$ 0.94	$ 0.64	$ 0.63	$ 0.46	$ (0.20)	$ 0.12	$ 0.14	$ 0.10	$ 0.10	$ 4.04	$ 1.62	$ 0.46
Anti-dilutive shares excluded in the computation of diluted earnings per share													83,000	18,000	1,000,000