Consolidated Statements Of Operations And Comprehensive Income (USD $) In Millions, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Oct. 01, 2010	Sep. 30, 2011	Oct. 01, 2010
Income Statement [Abstract]
Revenues	$ 898.0	$ 600.7	$ 2,674.4	$ 1,734.2
Cost of product revenues	636.9	354.2	1,904.8	1,015.8
Gross profit	261.1	246.5	769.6	718.4
Operating expenses:
Research and development	91.5	63.3	271.8	188.6
Selling and marketing	48.4	35.5	149.0	107.6
General and administrative	51.9	31.2	151.3	98.0
Amortization of acquisition-related intangible assets	10.6	7.9	31.7	23.8
Restructuring, asset impairments and other, net	65.4	0.9	82.9	7.0
Total operating expenses	267.8	138.8	686.7	425.0
Operating income (loss)	(6.7)	107.7	82.9	293.4
Other income (expenses), net:
Interest expense	(16.9)	(14.1)	(52.5)	(45.0)
Interest income	0.3	0.2	0.8	0.4
Other	(3.1)	(0.8)	(6.6)	(7.0)
Loss on debt repurchase	(5.3)	0	(5.3)	(0.7)
Gain on SANYO Semiconductor acquisition	0	0	58.0	0
Other income (expenses), net	(25.0)	(14.7)	(5.6)	(52.3)
Income (loss) before income taxes	(31.7)	93.0	77.3	241.1
Income tax provision	(17.3)	(4.6)	(21.3)	(9.4)
Net income (loss)	(49.0)	88.4	56.0	231.7
Less: Net income attributable to minority interests	(0.4)	(0.6)	(1.9)	(2.2)
Net income (loss) attributable to ON Semiconductor Corporation	(49.4)	87.8	54.1	229.5
Comprehensive income (loss):
Net income (loss)	(49.0)	88.4	56.0	231.7
Foreign currency translation adjustments	6.0	3.5	10.4	5.3
Amortization of prior service costs of defined benefit plan	0	0	0.2	0
Comprehensive income (loss)	(43.0)	91.9	66.6	237.0
Comprehensive income attributable to minority interests	(0.4)	(0.6)	0	(2.2)
Comprehensive income (loss) attributable to ON Semiconductor Corporation	$ (43.4)	$ 91.3	$ 66.6	$ 234.8
Net income (loss) per common share attributable to ON Semiconductor Corporation:
Basic	$ (0.11)	$ 0.20	$ 0.12	$ 0.53
Diluted	$ (0.11)	$ 0.20	$ 0.12	$ 0.52
Weighted average common shares outstanding:
Basic	448.8	431.6	445.5	430.0
Diluted	448.8	439.8	454.3	439.8