vue-router: navigate to nested state/route by name and params

How can I navigate to a child state using $router.push?

My routes:

const routes = [
  {
    path: "/customers", name: 'Customers',
    components: {content: CustomersMain},
    props: {header: true, content: false},
    children: [
      {
        path: '',
        component: CustomerDetailsEmpty
      },
      {
        path: ':id',
        name: 'CustomerDetails',
        component: CustomerDetails
      }
    ]
  }
];

How can I navigate to CustomerDetails with an id param set using $router.push?