Income taxes (Income tax examination) (Details)	12 Months Ended
	Dec. 31, 2011
United States
Income Tax Examination [Line Items]
Income Tax Examination, Year(s) under Examination	2008-2011
KOREA, REPUBLIC OF
Income Tax Examination [Line Items]
Income Tax Examination, Year(s) under Examination	2009-2011
PHILIPPINES
Income Tax Examination [Line Items]
Income Tax Examination, Year(s) under Examination	2008-2011
JAPAN
Income Tax Examination [Line Items]
Income Tax Examination, Year(s) under Examination	2006-2011
CHINA
Income Tax Examination [Line Items]
Income Tax Examination, Year(s) under Examination	2006-2011
SINGAPORE
Income Tax Examination [Line Items]
Income Tax Examination, Year(s) under Examination	2005-2011
TAIWAN, PROVINCE OF CHINA
Income Tax Examination [Line Items]
Income Tax Examination, Year(s) under Examination	2004-2011