How to change the type of column?

I have column balance with data type double, but I want to change it for storing price in proper way. I want to make it decimal.

For that I am trying I am doing following

public function up()
{
    Schema::table('billing', function (Blueprint $table) {
        //
        $table->decimal('balance', 8, 2)->change();
    });
}

But I am confused about down function, should I revert it back, I mean the previous data type?

Can someone kindly guide me about that, I will be thank full. Thank you

via Chebli Mohamed