Earnings Per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended												12 Months Ended
	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, 2010	Mar. 31, 2010	Dec. 31, 2009	Sep. 30, 2009	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2010
Earnings Per Common Share
Net Income (Loss) Attributable to Lannett common shareholders	$ 1,415	$ 1,718	$ 609	$ 206	$ (1,864)	$ (362)	$ 2,353	$ (404)	$ 2,816	$ 2,093	$ 55	$ 2,857	$ 3,948	$ (277)	$ 7,821
Weighted Average Common Shares Outstanding (Basic)													28,263,335	26,758,552	24,743,902
Effect of potentially dilutive options and restricted stock awards (in shares)													145,097		455,471
Weighted Average Common Shares Outstanding (Diluted)													28,408,432	26,758,552	25,199,373
Basic earnings (loss) per share (in dollars per share)	$ 0.05	$ 0.06	$ 0.02	$ 0.01	$ (0.07)	$ (0.01)	$ 0.09	$ (0.02)	$ 0.11	$ 0.08	$ 0.00	$ 0.12	$ 0.14	$ (0.01)	$ 0.32
Diluted earnings (loss) per share (in dollars per share)	$ 0.05	$ 0.06	$ 0.02	$ 0.01	$ (0.07)	$ (0.01)	$ 0.09	$ (0.02)	$ 0.11	$ 0.08	$ 0.00	$ 0.11	$ 0.14	$ (0.01)	$ 0.31
Anti-dilutive shares excluded in the computation of diluted earnings per share													2,321,000	2,100,000	1,281,000