Dividends (Details) (USD $)	0 Months Ended	3 Months Ended	12 Months Ended
Dec. 27, 2012	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Dividends, Common Stock [Abstract]
Payment of cash dividends			$ 12,072,000	$ 9,358,000	$ 8,646,000
Dividends paid per common share			$ 0.205	$ 0.15	$ 0.14
Accelerated cash dividend per share		$ 0.0425
Payment of accelerated cash dividends	$ 2,500,000

Cash outflow in the form of ordinary dividends to common shareholders, generally out of earnings.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 20

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 18

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3291-108585

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration