marsh crane fly
Tipula oleracea

The is a decent-sized crane fly, maybe the 2nd or 3rd largest I typically see in our stairwell each year. I'm making a huge guess as to species based on 1) its general look 2) the color markings on the wings and 3) the time of year. Initially, I thought it might be a common European crane fly (T. paludosa), but those only seem to fly in the fall. There's simply not much online information for CA crane flies. Powell and Hogue state there are 170 known Tipula species in CA.