Down and synthetic insulation need different treatment. For down sleeping bags and quilts, use a wash specifically formulated for down. Grangers Down Wash is the product Sea to Summit recommends, and it's also sold as part of a kit with drying balls that help re-loft the down in the dryer.
For synthetic-insulated bags, use a "performance" or technical wash such as Grangers Down Performance Wash rather than a down-specific soap. Both are far gentler than everyday laundry detergent and rinse out completely without leaving residue behind in the insulation.