Condensed Statement of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Consolidated net income	$ 1,131	$ 8,958	$ 4,367	$ 14,404
Change in unrealized loss on investments:
Changes arising during current period, net of tax benefit of $0, $0, $0 and $251, respectively	0	0	0	(349)
Reclassification for gain included in net income, net of tax expense of $0, $1,624, $0 and $2,997, respectively	0	(2,709)	0	(5,005)
Change in unrealized loss on investments:	0	(2,709)	0	(5,354)
Change in cumulative translation adjustment:
Changes arising during current period	1,548	(2,787)	(4,955)	(4,009)
Change in retirement plan actuarial losses:
Reclassification for gain included in net income, net of tax expense (benefit) of $0 for the three and six months ended March 31, 2015 and 2014	29	28	58	55
Change in retirement plan transition obligation:
Reclassification for gain included in net income, net of tax expense (benefit) of $0 for the three and six months ended March 31, 2015 and 2014	(14)	(15)	(29)	(30)
Other comprehensive income (loss)	1,563	(5,483)	(4,926)	(9,338)
Comprehensive income (loss)	2,694	3,475	(559)	5,066
Comprehensive income attributable to noncontrolling interest	(15)	(146)	(65)	(157)
Comprehensive income (loss) attributable to ISSI	$ 2,679	$ 3,329	$ (624)	$ 4,909