Consolidated Statement of Changes in Shareholders' Equity (Unaudited) (Parenthetical) (USD $) In Thousands, except Per Share data	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010
Shares of common stock issued upon conversion of Series B preferred stock	433,144
Retained earnings
Cash dividend, per share	$ 1.40	$ 1.40

Number of shares issued during the period as a result of the conversion of convertible securities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 29, 30
-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 12
-Paragraph 10

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Article 3

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 129
-Paragraph 4, 5

Name:	us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities
Namespace Prefix:	us-gaap
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration