I am trying to upload a csv file and creating object(code) using the contents of file.I have created a custom link on detail page of my custom object(line) like this(on click javascript) - window.top.location.href='/apex/Zip_Codes?Id={!Line__c.Id}'

I have also created class and a vf page to load the csv file. In vf page m using standard controller as Document and extension as my controller class.

But on clicking the custom link currently i am getting the below error-

Id value a0Sn00000005v0k is not valid for the Document standard controller

As per my observation this error is coming as it is passing 15 digit id to Document object and it is expecting a 18 digit id. What is the solution for this. Please help.thanks in advance.