Idaho became an official state in the USA in 1890 as the western parts of the country were slowly mapped out and became organized territories. Official vital records started being collected not long after.
Idaho birth records are considered private and confidential for 100 years after the birth date. And since the state only began collecting birth record information in 1911, that is not going to leave much room for doing any research. As the next few years go by there should be more records available that have become old enough for public access.
If you are trying to find information from before 1911, you can try individual counties. Some do have their own archives of records going back farther, but not usually any farther than the 1870s. You can also access the microfilm archives at the Idaho State Historical Society, where they have come records between 1907 and 1911 for most counties.
To access an Idaho birth record you will have to be an immediate relative, and provide proof of your identify and the relationship to the person on the record. You will need a photocopy of government issued photo ID (driver's license, passport or a Tribal ID card). For these purposes, you will have to be a parent, child, grandparent, grandchild, spouse or sibling to the person on the record. Cousins, aunts and uncles are not permitted access.