Duplicating Specific Rows in Spreadsheet

Hi All,
I'm trying to duplicate only specific rows in a spreadsheet. In my data, some rows have the same ID number, meaning they "match." Those that don't have a matching ID number need to be duplicated. For example:

ID Number Data
1 aaa
2 bbb
3 ccc
3 ddd
4 eee
5 fff
5 ggg

Needs to look like:

ID Number Data
1 aaa
1 aaa
2 bbb
2 bbb
3 ccc
3 ddd
4 eee
4 eee
5 fff
5 ggg

Any suggestions would be great. Thanks!