Load three table in laravel 5 using Eloquent

I have four tables.

customer_billing_header

id    |   customer_id    |    due_date
1     |   1              |    2016-01-01

customer_billing_details

id    |    header_id    |    bill_item_id
1     |    1            |    1
2     |    1            |    2
3     |    1            |    3

customer_bill_items

id    |    name
1     |    CCTV
2     |    Mouse
3     |    Keyboard

customer_monthly_bill

id    |    customer_id    |    bill_item_id
1     |    1              |    1

Now, I want to get the header and load the other three tables. I'm able to load only customer_billing_details. I don't know how to connect the customer_bill_items and customer_monthly_bill.

In my customer_billing_header model:

public function customer_billing_detail() {
    return $this->hasMany('App\Customer_Billing_Details', 'header_id');
}

In my controller:

public function show($id) {
    $headers = Customer_Billing_Header::where('customer_id', $id)->get();
    $headers->load('customer_billing_detail');
    return $headers;
}

I want to make like:

public function show($id) {
    $headers = Customer_Billing_Header::where('customer_id', $id)->get();
    $headers->load('customer_billing_detail', 'customer_bill_item', 'customer_monthly_bill');
}

via Chebli Mohamed