I found this phrase in the following excerpt from a novel (emphasis added):
New York cabbies were a unique breed. Fearless to a fault, they sped and swerved through crowded streets with unnatural calm.
I googled it between quotation marks and found almost 100.000 results. This somehow leads me to think that it is some sort of idiom or set phrase. Is it the case? Again, I can't understand its proper meaning: is it "so fearless that they may be faulted for that"?