Earnings (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Earnings (Loss) Per Common Share
Net income (loss) attributable to Lannett Company, Inc	$ 12,770	$ 14,929	$ 40,049	$ (6,307)
Basic weighted average common shares outstanding	37,136,945	36,849,208	37,064,781	36,785,829
Effect of potentially dilutive stock options, warrants and restricted stock awards	1,150,060	903,096	1,047,412
Diluted weighted average common shares outstanding	38,287,005	37,752,304	38,112,193	36,785,829
Earnings (loss) per common share attributable to Lannett Company, Inc.:
Basic (in dollars per share)	$ 0.34	$ 0.41	$ 1.08	$ (0.17)
Diluted (in dollars per share)	$ 0.33	$ 0.40	$ 1.05	$ (0.17)
Anti-dilutive shares excluded in the computation of diluted earnings per share	3,000,000	3,000,000	3,000,000	4,400,000