Basis of presentation (Details)	1 Months Ended
Mar. 31, 2011	Apr. 12, 2011
Basis of presentation (Details) [Abstract]
Stock split declared on common shares	2-for-1 stock
Percentage of stock dividend		100.00%

Description of the stock split arrangement. Also provide the retroactive effect given by a stock split that occurs after the balance date but before the release of financial statements.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section C

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 43
-Chapter 7
-Section B
-Paragraph 2, 15, 16

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