Subsequent Events (Details) (USD $)	0 Months Ended
Feb. 13, 2013	Nov. 01, 2012	Aug. 01, 2012	May 03, 2012	Feb. 15, 2012
Subsequent Events [Abstract]
Dividends declared date	Feb. 12, 2013	Oct. 31, 2012	Jul. 31, 2012	May 02, 2012	Feb. 14, 2012
Dividend amount to be paid, per common share	$ 0.2325	$ 0.225	$ 0.22	$ 0.215	$ 0.21
Date dividend is payable	Mar. 04, 2013	Nov. 26, 2012	Aug. 29, 2012	May 30, 2012	Mar. 12, 2012
Date shareholders must be on record for dividend	Feb. 25, 2013	Nov. 12, 2012	Aug. 13, 2012	May 16, 2012	Feb. 27, 2012

Aggregate dividends declared during the period for each share of common stock outstanding.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=6959260&loc=d3e187085-122770

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- Definition

Date the declared dividend will be paid, in CCYY-MM-DD format.

+ References

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- Definition

Date the dividend to be paid was declared, in CCYY-MM-DD format.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 32

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

Date the holder must own the stock to be entitled to the dividend, in CCYY-MM-DD format.

+ References

No definition available.

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