Summary of Significant Accounting Policies (Narrative) (Details) (USD $)	1 Months Ended	3 Months Ended
Jun. 30, 2011	Mar. 31, 2011	Mar. 31, 2010	Apr. 30, 2011	May 01, 2010
Summary of Significant Accounting Policies
Declaration date of dividends per common share	May 31, 2011	Jan. 31, 2011	Jan. 31, 2010
Dividends declared per common share	$ 0.22	$ 0.22	$ 0.16
Dividends per common share date to be paid	Jun. 30, 2011	Mar. 31, 2011	Mar. 31, 2010

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

+ References

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

The day, month, and year (YYYY-MM-DD) that the dividend declared as of or prior to the financial reporting date will be paid in the subsequent period.

+ 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

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- Definition

The day, month and year (YYYY-MM-DD) that the dividend to be paid was declared.

+ References

Reference 1: 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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

Reference 2: 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

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