Consolidated Balance Sheet (Parenthetical)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Statement of Financial Position [Abstract]
Common stock, shares outstanding	153,566,297	151,888,780	160,381,815	165,667,659

Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 12

-Paragraph 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

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-Name Regulation S-X (SX)

-Number 210

-Section 04

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

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-Name Accounting Standards Codification

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-Publisher SEC

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant