Cash, Cash Equivalents and Investments (Details) - USD ($) $ in Thousands	6 Months Ended
Jul. 04, 2015	Jan. 03, 2015
Available-for-sale securities
Available-for-sale securities, Cost	$ 215,115
Cash, cash equivalents and investments
Auction-rate securities guaranteed by the U.S. government	6,000
Auction-rate securities privately insured	2,000
Auction-rate securities having credit rating 'AA'	6,000
Auction-rate securities having credit rating 'A'	2,000
Other-than-temporary impairment losses	0
Cash on hand, Cost	65,449	$ 52,144
Cash on hand, Fair Value	65,449	52,144
Cash and cash equivalents, Cost	125,051	141,705
Cash and cash equivalents, Gross Unrealized Gains		1
Cash and cash equivalents, Fair Value	125,051	141,706
Cash Equivalents:
Available-for-sale securities
Available-for-sale securities, Cost	59,602	89,561
Available-for-sale securities, Gross Unrealized Gains		1
Available-for-sale securities, Fair Value	59,602	89,562
Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost	147,513	193,365
Available-for-sale securities, Gross Unrealized Losses	(54)	(73)
Available-for-sale securities, Gross Unrealized Gains	97	197
Available-for-sale securities, Fair Value	147,556	193,489
Long-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost	8,000	8,000
Available-for-sale securities, Gross Unrealized Losses	(821)	(581)
Available-for-sale securities, Fair Value	7,179	7,419
Money market funds \| Cash Equivalents:
Available-for-sale securities
Available-for-sale securities, Cost	43,689	71,415
Available-for-sale securities, Fair Value	43,689	71,415
Municipal bonds \| Cash Equivalents:
Available-for-sale securities
Available-for-sale securities, Cost	543	1,756
Available-for-sale securities, Gross Unrealized Gains		1
Available-for-sale securities, Fair Value	543	1,757
Municipal bonds \| Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost	122,148	129,005
Available-for-sale securities, Gross Unrealized Losses	(45)	(25)
Available-for-sale securities, Gross Unrealized Gains	96	172
Available-for-sale securities, Fair Value	122,199	129,152
Variable-rate demand notes \| Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost	14,495	12,915
Available-for-sale securities, Fair Value	14,495	12,915
Corporate bonds \| Cash Equivalents:
Available-for-sale securities
Available-for-sale securities, Cost		1,101
Available-for-sale securities, Fair Value		1,101
Corporate bonds \| Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost	7,431	33,043
Available-for-sale securities, Gross Unrealized Losses	(6)	(35)
Available-for-sale securities, Gross Unrealized Gains	1	25
Available-for-sale securities, Fair Value	7,426	33,033
International government bonds \| Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost	2,240	2,526
Available-for-sale securities, Gross Unrealized Losses	(3)	(10)
Available-for-sale securities, Fair Value	2,237	2,516
Commercial paper \| Cash Equivalents:
Available-for-sale securities
Available-for-sale securities, Cost	9,823	5,348
Available-for-sale securities, Fair Value	9,823	5,348
Commercial paper \| Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost	1,199	8,995
Available-for-sale securities, Fair Value	1,199	8,995
Certificates of deposit \| Cash Equivalents:
Available-for-sale securities
Available-for-sale securities, Cost	5,547	7,739
Available-for-sale securities, Fair Value	5,547	7,739
Certificates of deposit \| Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost		250
Available-for-sale securities, Fair Value		250
US government agency \| Cash Equivalents:
Available-for-sale securities
Available-for-sale securities, Cost		1,202
Available-for-sale securities, Fair Value		1,202
US government agency \| Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost		601
Available-for-sale securities, Fair Value		601
U.S. government bonds \| Cash Equivalents:
Available-for-sale securities
Available-for-sale securities, Cost		1,000
Available-for-sale securities, Fair Value		1,000
U.S. government bonds \| Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost		650
Available-for-sale securities, Fair Value		650
Asset-backed securities \| Short-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost		5,380
Available-for-sale securities, Gross Unrealized Losses		(3)
Available-for-sale securities, Fair Value		5,377
Auction rate securities \| Long-term Investments:
Available-for-sale securities
Available-for-sale securities, Cost	8,000	8,000
Available-for-sale securities, Gross Unrealized Losses	(821)	(581)
Available-for-sale securities, Fair Value	$ 7,179	$ 7,419

This element represents the amount of auction-rate securities that is guaranteed by the U.S. government.

No definition available.

Name:	slab_AuctionRateSecuritiesGuaranteedByUSGovernment
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents the amount of auction-rate securities having credit rating of 'A'.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

This element represents the amount of auction-rate securities having credit rating of 'AA'.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

This element represents the amount of auction-rate securities that is privately insured.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

This element represents the adjusted cost of cash and cash equivalents that are considered available-for-sale and recorded at fair value.

+ References

No definition available.

+ Details

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- Definition

This element represents the unrealized gains from cash and cash equivalents.

+ References

No definition available.

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- Definition

Represents fair value of cash which is similar to carrying value of cash as of balance sheet date.

+ References

No definition available.

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- Definition

This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

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-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.2)

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- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

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- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

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Balance Type:	credit
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- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

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- Definition

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Excludes cash and cash equivalents within disposal group and discontinued operation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash

-URI http://asc.fasb.org/extlink&oid=6506951

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 1

-Article 5

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

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Balance Type:	debit
Period Type:	instant

- References

No definition available.

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Period Type:	duration

- Definition

The amount by which the fair value of an investment in debt and equity securities categorized as Available-for-sale is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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