I'm pretty sure Roger Deakins has talked about how He light this scene in his forum but for the sake of discussion I'll take a crack at it.
Looks as though theres a large hard source outside the window creating that bright shaft of sunlight coming into the room. It's hard to tell by just looking at this one shot but the shafts do look like Roger may have had two sources for each window, each creating their own shaft of light that feels as though they came from one source. The shafts come from a higher angle as the shades act as a toper, preventing a hot backlight from hitting Jeff Bridges.
As far as fill goes there are two things happening. Looks as though a bounce card (pro unbleached muslim) is placed camera right, in order to bounce the shafts of light from the window back at Jeff Daniels giving him a nice soft key then add some smoke to bring out the shafts and act as room fill and there you have it.