CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Statement of Stockholders' Equity [Abstract]
Dividend declared per share (in dollars per share)	$ 0.40	$ 0.40	$ 0.40
Changes in unrealized gains (losses) on marketable securities, tax	$ 0	$ 58	$ (83)
Actuarial gain or loss arising in the year, tax	$ (74)	$ 161	$ 115