Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Statement of Comprehensive Income [Abstract]
Consolidated net income (loss)	$ 23,489	$ 17,744	$ (2,605)
Change in unrealized gain (loss) on investments:
Changes arising during current year, net of tax benefit (expense) of $251, $(7,975) and $312 for fiscal 2014, 2013 and 2012, respectively	(349)	13,755	(1,523)
Reclassification for (gain) loss included in net income (loss), net of tax expense (benefit) of $3,589, $3,823 and $(716) for fiscal 2014, 2013 and 2012, respectively	(6,029)	(5,854)	1,213
Net change	(6,378)	7,901	(310)
Change in cumulative translation adjustment:
Changes arising during current year	(3,736)	(1,261)	3,932
Translation adjustment, net change	(3,736)	(1,261)	3,932
Change in retirement plan transition obligation:
Changes arising during current year, net of tax benefit (expense) of $3, $(44) and $(119) for fiscal 2014, 2013 and 2012, respectively	(1)	(23)	(134)
Reclassification for gain included in net income (loss), net of tax expense (benefit) of $21, $15 and $0 for fiscal 2014, 2013 and 2012	(38)	(45)	(62)
Transition obligation, net change	(39)	(68)	(196)
Change in retirement plan actuarial losses:
Changes arising during current year, net of tax benefit (expense) of $28, $160 and $323 for fiscal 2014, 2013 and 2012, respectively	(100)	63	127
Reclassification for gain included in net income (loss), net of tax expense (benefit) of $(21), $(13) and $0 for fiscal 2014, 2013 and 2012	88	87	98
Actuarial Losses, net change	(12)	150	225
Other comprehensive income (loss)	(10,165)	6,722	3,651
Comprehensive income	13,324	24,466	1,046
Comprehensive income attributable to noncontrolling interests	(224)	(196)	(113)
Comprehensive income attributable to ISSI	$ 13,100	$ 24,270	$ 933