Employee Benefits and Retirement Plans - Summary of Stock Options (Details) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Compensation and Retirement Disclosure [Abstract]
Number of stock options granted	0	0	0
Average fair value of stock options granted	$ 0	$ 0	$ 0
Number of option shares exercisable	10,900	10,900	13,880
Average price of stock options exercisable	$ 20.19	$ 20.19	$ 19.08

The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iii)

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

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(1)(c)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

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Balance Type:	na
Period Type:	instant