Securities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Apr. 01, 2012 Y
Investment Holdings [Line Items]
Investments, market value	$ 27.5
Minimum maturity duration of contractual maturities of auction rate securities, years	10
Auction Rate Securities [Member]
Investment Holdings [Line Items]
Investments, market value	27.0
Structured Obligations Of Special Purpose Reinsurance Entities [Member] \| Auction Rate Securities [Member]
Investment Holdings [Line Items]
Investments, market value	18.8
Corporate Debt Securities [Member] \| Auction Rate Securities [Member]
Investment Holdings [Line Items]
Investments, market value	$ 8.2

This item represents the fair value of debt securities which are expected to mature after ten years from the balance sheet date which are categorized neither as held-to-maturity nor trading securities.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 20

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 320

-Section 50

-Paragraph 3

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62586-112803

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a),(d)

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27161-111563

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