Guarantor And Non-Guarantor Statements (Notes To Consolidated Statement Of Balance Sheet) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Sep. 28, 2012	Jun. 29, 2012	Mar. 30, 2012	Dec. 31, 2011		Dec. 31, 2010	Dec. 31, 2009
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 486.9		$ 421.4	$ 517.8	$ 580.1	$ 652.9		$ 623.3	$ 525.7
Short-term investments	144.8					248.6
Receivables, net	357.8					457.2
Inventories	581.7					637.4
Short-term intercompany receivables	0					0
Other current assets	111.7	[1]				121.6	[1]
Deferred income taxes	10.5					10.0
Total current assets	1,693.4					2,127.7
Property, plant and equipment, net	1,103.3	[2]				1,109.5	[2]	864.3
Deferred income taxes	31.2					34.2
Goodwill	184.6					198.7		191.2
Intangible assets, net	257.0					337.2
Long-term intercompany receivables	0					0
Other assets	58.9					76.2
Total assets	3,328.4					3,883.5
Accounts payable	279.5					451.8
Accrued expenses	228.3					239.8
Income taxes payable	4.9					7.5
Accrued interest	0.6					0.7
Deferred income on sales to distributors	134.5					172.0
Deferred income taxes	22.9					33.6
Current portion of long-term debt	353.6					370.1
Short-term intercompany payables	0					0
Total current liabilities	1,024.3					1,275.5
Long-term debt	658.3					836.9
Other long-term liabilities	232.2					260.1
Deferred income taxes	22.9					17.5
Long-term intercompany payables	0					0
Total liabilities	1,937.7					2,390.0
Common stock	5.1					5.0
Additional paid-in capital	3,156.4					3,113.5
Accumulated other comprehensive loss	(41.1)					(46.7)
Accumulated deficit	(1,292.9)					(1,202.3)
Less: treasury stock, at cost	(466.4)					(401.3)
Total ON Semiconductor Corporation stockholders’ equity	1,361.1					1,468.2
Non-controlling interest in consolidated subsidiaries	29.6					25.3		22.0
Total stockholders' equity	1,390.7					1,493.5		1,388.0	1,004.6
Total liabilities and equity	3,328.4					3,883.5
Issuer [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0		0	0	0	0		0	0
Short-term investments	0					0
Receivables, net	0					0
Inventories	0					0
Short-term intercompany receivables	0					0
Other current assets	0					0
Deferred income taxes	0					0
Total current assets	0					0
Property, plant and equipment, net	0					0
Deferred income taxes	0					0
Goodwill	0					0
Intangible assets, net	0					0
Long-term intercompany receivables	0					0
Other assets	1,834.9					2,036.2
Total assets	1,834.9					2,036.2
Accounts payable	0					0
Accrued expenses	0					0
Income taxes payable	0					0
Accrued interest	0.5					0.6
Deferred income on sales to distributors	0					0
Deferred income taxes	0					0
Current portion of long-term debt	198.9					182.6
Short-term intercompany payables	0					0
Total current liabilities	199.4					183.2
Long-term debt	274.1					384.5
Other long-term liabilities	0					0
Deferred income taxes	0					0
Long-term intercompany payables	0.3					0.3
Total liabilities	473.8					568.0
Common stock	5.1					5.0
Additional paid-in capital	3,156.4					3,113.5
Accumulated other comprehensive loss	(41.1)					(46.7)
Accumulated deficit	(1,292.9)					(1,202.3)
Less: treasury stock, at cost	(466.4)					(401.3)
Total ON Semiconductor Corporation stockholders’ equity	1,361.1					1,468.2
Non-controlling interest in consolidated subsidiaries	0					0
Total stockholders' equity	1,361.1					1,468.2
Total liabilities and equity	1,834.9					2,036.2
SCI LLC [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	212.1		156.0	249.7	232.7	304.5		392.3	286.0
Short-term investments	144.8					248.6
Receivables, net	45.4					64.7
Inventories	34.5					36.2
Short-term intercompany receivables	0					0
Other current assets	10.6					7.5
Deferred income taxes	2.3					5.5
Total current assets	449.7					667.0
Property, plant and equipment, net	272.0					255.2
Deferred income taxes	0					0
Goodwill	111.7					125.7
Intangible assets, net	128.2					152.3
Long-term intercompany receivables	310.8					348.8
Other assets	1,287.1					1,303.5
Total assets	2,559.5					2,852.5
Accounts payable	24.1					32.8
Accrued expenses	53.0					61.0
Income taxes payable	0					(0.1)
Accrued interest	0					0
Deferred income on sales to distributors	34.2					43.7
Deferred income taxes	0					0
Current portion of long-term debt	80.2					74.1
Short-term intercompany payables	20.5					30.6
Total current liabilities	212.0					242.1
Long-term debt	344.1					393.8
Other long-term liabilities	27.5					26.6
Deferred income taxes	2.4					5.5
Long-term intercompany payables	0					0
Total liabilities	586.0					668.0
Common stock	0.3					0.3
Additional paid-in capital	2,549.3					2,711.2
Accumulated other comprehensive loss	(41.0)					(46.7)
Accumulated deficit	(535.1)					(480.3)
Less: treasury stock, at cost	0					0
Total ON Semiconductor Corporation stockholders’ equity	1,973.5					2,184.5
Non-controlling interest in consolidated subsidiaries	0					0
Total stockholders' equity	1,973.5					2,184.5
Total liabilities and equity	2,559.5					2,852.5
Other Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0		0	0	(0.9)	(0.2)		0	0
Short-term investments	0					0
Receivables, net	0					0
Inventories	0					0
Short-term intercompany receivables	3.3					3.4
Other current assets	0					0
Deferred income taxes	0					0
Total current assets	3.3					3.2
Property, plant and equipment, net	2.8					2.3
Deferred income taxes	0					0
Goodwill	37.2					37.3
Intangible assets, net	0					0
Long-term intercompany receivables	51.0					51.1
Other assets	78.5					59.1
Total assets	172.8					153.0
Accounts payable	0					0.1
Accrued expenses	0.9					0.8
Income taxes payable	0					0
Accrued interest	0					0
Deferred income on sales to distributors	0					0
Deferred income taxes	0					0
Current portion of long-term debt	0.1					0
Short-term intercompany payables	0					0
Total current liabilities	1.0					0.9
Long-term debt	0					0
Other long-term liabilities	0.3					0.4
Deferred income taxes	0					0
Long-term intercompany payables	0					0
Total liabilities	1.3					1.3
Common stock	50.9					50.9
Additional paid-in capital	259.2					238.4
Accumulated other comprehensive loss	0					0
Accumulated deficit	(138.6)					(137.6)
Less: treasury stock, at cost	0					0
Total ON Semiconductor Corporation stockholders’ equity	171.5					151.7
Non-controlling interest in consolidated subsidiaries	0					0
Total stockholders' equity	171.5					151.7
Total liabilities and equity	172.8					153.0
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	274.8		265.4	268.1	348.3	348.6		231.0	239.7
Short-term investments	0					0
Receivables, net	312.4					392.5
Inventories	578.4					599.3
Short-term intercompany receivables	17.2					27.2
Other current assets	101.1					114.1
Deferred income taxes	8.2					4.5
Total current assets	1,292.1					1,486.2
Property, plant and equipment, net	830.9					854.5
Deferred income taxes	8.5					34.2
Goodwill	35.7					35.7
Intangible assets, net	154.7					215.0
Long-term intercompany receivables	0					0
Other assets	827.3					846.9
Total assets	3,149.2					3,472.5
Accounts payable	255.4					418.9
Accrued expenses	172.7					176.3
Income taxes payable	4.9					7.6
Accrued interest	0.1					0.1
Deferred income on sales to distributors	100.3					128.3
Deferred income taxes	0.1					33.6
Current portion of long-term debt	74.4					113.4
Short-term intercompany payables	0					0
Total current liabilities	607.9					878.2
Long-term debt	40.1					58.6
Other long-term liabilities	204.4					233.1
Deferred income taxes	20.5					12.0
Long-term intercompany payables	156.0					194.1
Total liabilities	1,028.9					1,376.0
Common stock	201.6					146.9
Additional paid-in capital	1,402.9					1,359.2
Accumulated other comprehensive loss	(34.6)					(39.2)
Accumulated deficit	550.4					629.6
Less: treasury stock, at cost	0					0
Total ON Semiconductor Corporation stockholders’ equity	2,120.3					2,096.5
Non-controlling interest in consolidated subsidiaries	0					0
Total stockholders' equity	2,120.3					2,096.5
Total liabilities and equity	3,149.2					3,472.5
Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0		0	0	0	0		0	0
Short-term investments	0					0
Receivables, net	0					0
Inventories	(31.2)					1.9
Short-term intercompany receivables	(20.5)					(30.6)
Other current assets	0					0
Deferred income taxes	0					0
Total current assets	(51.7)					(28.7)
Property, plant and equipment, net	(2.4)					(2.5)
Deferred income taxes	22.7					0
Goodwill	0					0
Intangible assets, net	(25.9)					(30.1)
Long-term intercompany receivables	(361.8)					(399.9)
Other assets	(3,968.9)					(4,169.5)
Total assets	(4,388.0)					(4,630.7)
Accounts payable	0					0
Accrued expenses	1.7					1.7
Income taxes payable	0					0
Accrued interest	0					0
Deferred income on sales to distributors	0					0
Deferred income taxes	22.8					0
Current portion of long-term debt	0					0
Short-term intercompany payables	(20.5)					(30.6)
Total current liabilities	4.0					(28.9)
Long-term debt	0					0
Other long-term liabilities	0					0
Deferred income taxes	0					0
Long-term intercompany payables	(156.3)					(194.4)
Total liabilities	(152.3)					(223.3)
Common stock	(252.8)					(198.1)
Additional paid-in capital	(4,211.4)					(4,308.8)
Accumulated other comprehensive loss	75.6					85.9
Accumulated deficit	123.3					(11.7)
Less: treasury stock, at cost	0					0
Total ON Semiconductor Corporation stockholders’ equity	(4,265.3)					(4,432.7)
Non-controlling interest in consolidated subsidiaries	29.6					25.3
Total stockholders' equity	(4,235.7)					(4,407.4)
Total liabilities and equity	$ (4,388.0)					$ (4,630.7)

[1] Included in other current assets are $1.0 million of fixed assets that are held-for-sale as of December 31, 2012.

[2] Included in property, plant and equipment are $8.3 million of fixed assets that are held-for-sale as of December 31, 2012.