Benefit Obligations - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Interest per year on cash-balance accounts	4.00%
Target asset allocation for plan assets in public equity securities	50.00%
Target asset allocation for plan assets in fixed-income securities	42.50%
Target asset allocation for plan assets in real estate securities	7.50%
Current target allocations for post-retirement benefit plan assets in equity securities	40.00%
Current target allocations for post-retirement benefit plan assets in fixed-income securities	60.00%
Actual gain on plan assets	$ 117,100,000
Gains smoothing period	5 years
Description of the defined contribution plan	Eligible employees in the U.S. may participate in the LSI Corporation 401(k) Plan (“401(k) Plan”). The 401(k) Plan provides for tax-deferred salary contributions and after-tax contributions for eligible employees. The Plan allows employees to contribute from 1% to 50% of their annual compensation on a pretax and after-tax and effective June 1, 2012, the Plan also allows employees to make Roth contributions. Employee contributions are limited to a maximum annual amount as set periodically by the Internal Revenue Code. The Company matches pretax employee contributions up to 100% of the first 2% of eligible earnings that are contributed by employees and may make additional variable matching contributions based on the Company’s performance. The maximum matching contribution that the Company may allocate to each participant’s account will not exceed $11,250 for the 2012 due to the $250,000 annual limit on eligible earnings imposed by the Internal Revenue Code. All matching contributions vest immediately except that matching contribution for new employees are fully vested after two years of service.
Company's matching percentage on employee's eligible earnings	2.00%
Minimum employees contribution percentage	1.00%
Maximum employees contribution percentage	50.00%
Maximum contribution amount by the Company per employee	11,250
Annual limit by Internal Revenue Code of eligible earnings for matching contributions	250,000
Foreign pension plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Obligations related to the Company's international pension plans	28,800,000	22,200,000
Fair value of assets for Pension plans	13,600,000	12,300,000
Accumulated benefit obligation	26,700,000	20,500,000
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of assets for Pension plans	993,231,000	867,241,000
Company contributions	51,700,000
Defined Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated net actuarial loss that will be amortized from accumulated other comprehensive loss into pension costs	18,400,000
Estimated net actuarial loss that will be amortized from accumulated other comprehensive loss into post-retirement costs	1,500,000
Defined Contribution Pension [Member]
Defined Benefit Plan Disclosure [Line Items]
Company contributions	$ 22,800,000	$ 18,700,000	$ 20,500,000