Triminion

Description
Triminion is a variant of Dominion, in which triominoes must be placed to divide the grid into separate areas.

Rules
The challenge is to divide the grid into separate areas subject to the following rules:
 * 1) Each area has all copies of a single letter, but only that letter.
 * 2) Shaded triominoes divide the grid and can only touch at corners.
 * 3) Identical triominoes are not allowed to touch diagonally.
 * 4) Cells with letters are always unshaded.
 * 5) All regions must have at least one letter contained in it.

Example
A standard 10x10 Triminion and its solution.