000000 - Document - Document and Entity Information {Elements} link:presentationLink link:calculationLink link:definitionLink 000021 - Disclosure - Risk/Return Detail Data {Elements} - William Blair Growth Fund link:presentationLink link:calculationLink link:definitionLink 000021 - Schedule - Annual Fund Operating Expenses link:calculationLink link:presentationLink link:definitionLink 000041 - Disclosure - Risk/Return Detail Data {Elements} - William Blair Large Cap Growth Fund link:presentationLink link:calculationLink link:definitionLink 000061 - Disclosure - Risk/Return Detail Data {Elements} - William Blair Mid Cap Value Fund link:presentationLink link:calculationLink link:definitionLink 000081 - Disclosure - Risk/Return Detail Data {Elements} - William Blair Small-Mid Cap Core Fund link:presentationLink link:calculationLink link:definitionLink 000101 - Disclosure - Risk/Return Detail Data {Elements} - William Blair Small-Mid Cap Growth Fund link:presentationLink link:calculationLink link:definitionLink 000121 - Disclosure - Risk/Return Detail Data {Elements} - William Blair Small-Mid Cap Value Fund link:presentationLink link:calculationLink link:definitionLink 000141 - Disclosure - Risk/Return Detail Data {Elements} - William Blair Small Cap Growth Fund link:presentationLink link:calculationLink link:definitionLink 000161 - Disclosure - Risk/Return Detail Data {Elements} - William Blair Small Cap Value Fund link:presentationLink link:calculationLink link:definitionLink 000181 - Disclosure - Risk/Return Detail Data {Elements} - William Blair Global Leaders Fund link:presentationLink link:calculationLink link:definitionLink 000201 - Disclosure - Risk/Return Detail Data {Elements} - William Blair International Leaders Fund link:presentationLink link:calculationLink link:definitionLink 000221 - Disclosure - Risk/Return Detail Data {Elements} - William Blair International Growth Fund link:presentationLink link:calculationLink link:definitionLink 000241 - Disclosure - Risk/Return Detail Data {Elements} - William Blair Institutional International Growth Fund link:presentationLink link:calculationLink link:definitionLink 000261 - Disclosure - Risk/Return Detail Data {Elements} - William Blair International Small Cap Growth Fund link:presentationLink link:calculationLink link:definitionLink 000281 - Disclosure - Risk/Return Detail Data {Elements} - William Blair Emerging Markets Leaders Fund link:presentationLink link:calculationLink link:definitionLink 000301 - Disclosure - Risk/Return Detail Data {Elements} - William Blair Emerging Markets Growth Fund link:presentationLink link:calculationLink link:definitionLink 000321 - Disclosure - Risk/Return Detail Data {Elements} - William Blair Emerging Markets ex China Growth Fund link:presentationLink link:calculationLink link:definitionLink 000341 - Disclosure - Risk/Return Detail Data {Elements} - William Blair Emerging Markets Small Cap Growth Fund link:presentationLink link:calculationLink link:definitionLink 000361 - Disclosure - Risk/Return Detail Data {Elements} - William Blair China Growth Fund link:presentationLink link:calculationLink link:definitionLink 000381 - Disclosure - Risk/Return Detail Data {Elements} - William Blair Emerging Markets Debt Fund link:presentationLink link:calculationLink link:definitionLink