Goodwill And Intangible Assets (Summary Of Reconciliation Of Cost Of Goodwill) (Details) (USD $) In Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2011	Dec. 31, 2010
Goodwill	$ 623.9	$ 615.9
Accumulated Amortization	(9.8)	(9.8)
Goodwill, Impaired, Accumulated Impairment Loss	(414.9)	(414.9)
Carrying Value	199.2	191.2
Goodwill Acquired	8.0
Purchase Price Adjustments	0
Accumulated Impairment Losses	0
Automotive & Power Group: Analog Automotive [Member] | Cherry Acquisition [Member]
Goodwill	21.8	21.8
Accumulated Amortization	(4.2)	(4.2)
Goodwill, Impaired, Accumulated Impairment Loss	0	0
Carrying Value	17.6	17.6
Goodwill Acquired	0
Purchase Price Adjustments	0
Accumulated Impairment Losses	0
Computing & Consumer Products: Signal and Interface [Member] | Cherry Acquisition [Member]
Goodwill	29.1	29.1
Accumulated Amortization	(5.6)	(5.6)
Goodwill, Impaired, Accumulated Impairment Loss	0	0
Carrying Value	23.5	23.5
Goodwill Acquired	0
Purchase Price Adjustments	0
Accumulated Impairment Losses	0
Standard Products: Small Signal [Member] | Leshan Additional Interest [Member]
Goodwill	3.8	3.8
Accumulated Amortization	0	0
Goodwill, Impaired, Accumulated Impairment Loss	0	0
Carrying Value	3.8	3.8
Goodwill Acquired	0
Purchase Price Adjustments	0
Accumulated Impairment Losses	0
Digital & Mixed-Signal Product Group: Industrial [Member] | AMIS Acquisition [Member]
Goodwill	238.7	238.7
Accumulated Amortization	0	0
Goodwill, Impaired, Accumulated Impairment Loss	(214.7)	(214.7)
Carrying Value	24.0	24.0
Goodwill Acquired	0
Purchase Price Adjustments	0
Accumulated Impairment Losses	0
Digital & Mixed-Signal Product Group: Foundry [Member] | AMIS Acquisition [Member]
Goodwill	146.2	146.2
Accumulated Amortization	0	0
Goodwill, Impaired, Accumulated Impairment Loss	(131.4)	(131.4)
Carrying Value	14.8	14.8
Goodwill Acquired	0
Purchase Price Adjustments	0
Accumulated Impairment Losses	0
Digital & Mixed-Signal Product Group: Medical Products [Member] | AMIS Acquisition [Member]
Goodwill	79.7	79.7
Accumulated Amortization	0	0
Goodwill, Impaired, Accumulated Impairment Loss	(59.9)	(59.9)
Carrying Value	19.8	19.8
Goodwill Acquired	0
Purchase Price Adjustments	0
Accumulated Impairment Losses	0
Digital & Mixed-Signal Product Group: Medical Products [Member] | SDT Acquisition [Member]
Goodwill	8.7	8.7
Accumulated Amortization	0	0
Goodwill, Impaired, Accumulated Impairment Loss	0	0
Carrying Value	8.7	8.7
Goodwill Acquired	0
Purchase Price Adjustments	0
Accumulated Impairment Losses	0
Digital & Mixed-Signal Product Group: Military or Aerospace [Member] | AMIS Acquisition [Member]
Goodwill	44.8	44.8
Accumulated Amortization	0	0
Goodwill, Impaired, Accumulated Impairment Loss	0	0
Carrying Value	44.8	44.8
Goodwill Acquired	0
Purchase Price Adjustments	0
Accumulated Impairment Losses	0
Standard Products: Memory Products [Member] | Catalyst Acquisition [Member]
Goodwill	14.1	14.1
Accumulated Amortization	0	0
Goodwill, Impaired, Accumulated Impairment Loss	0	0
Carrying Value	14.1	14.1
Goodwill Acquired	0
Purchase Price Adjustments	0
Accumulated Impairment Losses	0
Digital & Mixed-Signal Product Group: Protection Products [Member] | PulseCore Acquisition [Member]
Goodwill	8.9	8.9
Accumulated Amortization	0	0
Goodwill, Impaired, Accumulated Impairment Loss	(8.9)	(8.9)
Carrying Value	0	0
Goodwill Acquired	0
Purchase Price Adjustments	0
Accumulated Impairment Losses	0
Standard Products: Filter Products [Member] | CMD Acquisition [Member]
Goodwill	20.1	20.1
Accumulated Amortization	0	0
Goodwill, Impaired, Accumulated Impairment Loss	0	0
Carrying Value	20.1	20.1
Goodwill Acquired	0
Purchase Price Adjustments	0
Accumulated Impairment Losses	0
Digital & Mixed-Signal Product Group: Sensor Products [Member] | ISBU Acquisition [Member]
Goodwill	8.0	0
Accumulated Amortization	0	0
Goodwill, Impaired, Accumulated Impairment Loss	0	0
Carrying Value	8.0	0
Goodwill Acquired	8.0
Purchase Price Adjustments	0
Accumulated Impairment Losses	$ 0