We packed the travel bottle (from Target) of liquid Tide last year and took the same precautions to seal it in a baggie. It was in my checked luggage and I had no problem.
This year, I was fortunate enough to find the little single-load boxes of Tide at a nearby Safeway. This is the same size box you would get out of a laundromat vending machine. The boxes were in the travel section of the store and cost 79 cents each, which means doing more than one load of laundry would cost more than with the liquid (two loads with powder would cost $1.58 because I would need two of the small boxes, but two loads with liquid would cost 99 cents, and I think theres enough liquid for 4 or 6 loads). But, the boxes are lighter and IF they should spill it would not be as messy as a liquid. Plus, if TSA should randomly pick my suitcase to search, the detergent is in a clearly marked and sealed box so it is easily identified as harmless.