Summary Of Significant Accounting Policies (Narrative) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Summary Of Significant Accounting Policies [Line Items]
Research and development expense	$ 3,957	$ 2,361	$ 2,285
Advertising expense	920	877	748
Stock-based compensation expense	2,434	1,481	1,287
Income tax benefit recognized related to stock-based compensation	$ 901	$ 537	$ 475
Weighted-average fair value granted	$ 51.89	$ 62.17	$ 61.51
Nagase-Landauer Ltd [Member]
Summary Of Significant Accounting Policies [Line Items]
Equity method investment, ownership percentage	50.00%
Buildings [Member]
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	30 years
Equipment [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	8 years
Equipment [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	3 years
Internal Software [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	10 years
Internal Software [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	5 years
Dosimetry Devices, Principally Badges, And Software [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	8 years
Dosimetry Devices, Principally Badges, And Software [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	30 months