Income (Loss) Per Common Share (Computation Of Net Income Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Income (Loss) Per Common Share [Abstract]
Net income (loss) attributed to Landauer, Inc.	$ 2,566	$ 7,265	$ 4,279	$ 3,643	$ 2,564	$ 4,055	$ 3,547	$ 4,377	$ 17,753	$ 14,543	$ (25,203)
Less: Income allocated to unvested restricted stock									79	86
Net (loss) income available to common stockholders									$ 17,674	$ 14,457	$ (25,203)
Basic weighted averages shares outstanding	9,532,000	9,531,000	9,518,000	9,460,000	9,533,000	9,509,000	9,493,000	9,446,000	9,526,000	9,511,000	9,524,000
Net income (loss) per share – Basic	$ 0.27	$ 0.76	$ 0.45	$ 0.38	$ 0.27	$ 0.42	$ 0.37	$ 0.46	$ 1.86	$ 1.52	$ (2.65)
Effect of dilutive securities									43,000	29,000
Diluted weighted averages shares outstanding	9,584,000	9,564,000	9,550,000	9,492,000	9,570,000	9,534,000	9,520,000	9,474,000	9,569,000	9,540,000	9,524,000
Net income (loss) per share – Diluted	$ 0.26	$ 0.76	$ 0.45	$ 0.38	$ 0.27	$ 0.42	$ 0.37	$ 0.46	$ 1.85	$ 1.52	$ (2.65)