Killer Plus Minus Samurai puzzle

If you’re a Sudoku Xtra reader you’ll have seen these in their regular 9×9 form in both issues 5 and 6, but this is the first time I’ve made a Samurai one, and the first time I’ve posted one here I think.

This is essentially a regular Killer Sudoku puzzle, except that instead of placing 1 to 9 you must place -4, -3, -2, -1, 0, 1, 2, 3 and 4 into each row, column and bold-lined 3×3 box.  There are also two overlapping 9×9 grids to solve simultaneously.

As in regular Killer, the values in each dashed-line cage must sum to the given total, and you cannot repeat the same number within any one cage.

Good luck! :)