Income taxes (Details)	6 Months Ended
Jun. 30, 2011
Estimated annual effective tax rate (in hundredths)	27.00%
Statutory corporate tax rate (in hundredths)	35.00%

The domestic federal statutory tax rate applicable under enacted tax laws to the Company's pretax income from continuing operations for the period. The "statutory" tax rate shall be the regular tax rate if there are alternative tax systems.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 109
-Paragraph 47

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