Consolidated Statements Of Comprehensive Income (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 28, 2012	Sep. 30, 2011	Sep. 28, 2012	Sep. 30, 2011
Income Statement [Abstract]
Revenues	$ 725.5	$ 898.0	$ 2,214.7	$ 2,674.4
Cost of product revenues	487.5	636.9	1,473.2	1,904.8
Gross profit	238.0	261.1	741.5	769.6
Operating expenses:
Research and development	90.1	91.5	279.3	271.8
Selling and marketing	44.2	48.4	136.8	149.0
General and administrative	36.8	51.9	119.7	151.3
Amortization of acquisition-related intangible assets	11.1	10.6	33.3	31.7
Restructuring, asset impairments and other, net	11.2	65.4	57.3	82.9
Total operating expenses	193.4	267.8	626.4	686.7
Operating Income	44.6	(6.7)	115.1	82.9
Other income (expenses), net:
Interest expense	(13.6)	(16.9)	(43.4)	(52.5)
Interest income	0.3	0.3	1.1	0.8
Other	(3.6)	(3.1)	3.4	(6.6)
Loss on debt repurchase	(7.8)	(5.3)	(7.8)	(5.3)
Gain on SANYO Semiconductor acquisition	0	0	0	24.3
Other income (expenses), net	(24.7)	(25.0)	(46.7)	(39.3)
Income before income taxes	19.9	(31.7)	68.4	43.6
Income tax provision	(6.5)	(17.3)	(17.8)	(21.3)
Net income	13.4	(49.0)	50.6	22.3
Less: Net income attributable non-controlling interest	(0.9)	(0.4)	(3.0)	(1.9)
Net income attributable to ON Semiconductor Corporation	12.5	(49.4)	47.6	20.4
Comprehensive income:
Foreign currency translation adjustments	(2.1)	6.0	0.2	10.4
Effects of cash flow hedges	1.8	0	1.1	0
Unrealized gain (loss) on available-for-sale securities	(0.2)	0	0.1	0
Amortization of prior service costs of defined benefit plan	0	0	0.1	0.2
Comprehensive income	12.9	(43.0)	52.1	32.9
Comprehensive income attributable to non-controlling interests	(0.9)	(0.4)	(3.0)	(1.9)
Comprehensive income attributable to ON Semiconductor Corporation	$ 12.0	$ (43.4)	$ 49.1	$ 31.0
Net income per common share attributable to ON Semiconductor Corporation:
Basic	$ 0.03	$ (0.11)	$ 0.10	$ 0.05
Diluted	$ 0.03	$ (0.11)	$ 0.10	$ 0.04
Weighted average common shares outstanding:
Basic	454.6	448.8	453.9	445.5
Diluted	456.2	448.8	458.2	454.3