Fair Value Measurements (Details 4) (Auction rate securities, Discounted cash flow, USD $) In Thousands, unless otherwise specified	9 Months Ended
Sep. 28, 2013
Quantitative information for Level 3 Fair Value Measurements Assets
Fair value Assets	$ 8,960
Weighted Average
Quantitative information for Level 3 Fair Value Measurements Assets
Discount rate (as a percent)	1.40%
Market credit spread (as a percent)	3.15%
Liquidity factor (as a percent)	0.00%

Represents the liquidity factor, used as an input to measure fair value.

No definition available.

Name:	thor_FairValueInputsLiquidityFactor
Namespace Prefix:	thor_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the market credit spread, used as an input to measure fair value.

+ References

No definition available.

+ Details

Name:	thor_FairValueInputsMarketCreditSpread
Namespace Prefix:	thor_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

+ Details

Name:	us-gaap_AssetsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FairValueInputsAssetsQuantitativeInformationLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (bbb)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueInputsDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration