Stock Based Compensation (Details) (2005 Employee Stock Plan [Member], USD $)	3 Months Ended
Mar. 31, 2013
2/16/2012 [Member]
Restricted stock compensation footnote
Shares Granted	2,000
Fair Value	$ 30.48
Vesting Period	Ratably over 3 years from grant date
4/5/2012 [Member]
Restricted stock compensation footnote
Shares Granted	93,800
Fair Value	$ 31.51
Vesting Period	Ratably over 5 years from grant date

Description of pertinent provisions of equity-based compensation awards that have actual or potential impact upon the company's financial statements.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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