$array_a = array(0 =>
	array('Document' =>
		array('id' => 1)),
	array('Document' =>
		array('id' => 2)),
	array('Document' =>
		array('id' => 3)),
	);


$array_b = array(0 =>
	array('Document' =>
		array('id' => 2)),
	array('Document' =>
		array('id' => 2)),
	array('Document' =>
		array('id' => 4)),
	);

$result = array_intersect($array_a, $array_b);