as a rule

  1. (idiomatic) In general; most often.
    We go fishing every Sunday as a rule, but today the lake is frozen.
    • 1907, Robert W[illiam] Chambers, “chapter II”, in The Younger Set (Project Gutenberg; EBook #14852), New York, N.Y.: A. L. Burt Company, published 1 February 2005 (Project Gutenberg version), OCLC 4241346:
      His forefathers had been, as a rule, professional men—physicians and lawyers; his grandfather died under the walls of Chapultepec Castle while twisting a tourniquet for a cursing dragoon; an uncle remained indefinitely at Malvern Hill; [].
    • 1918, William Strunk, Jr., The Elements of Style:
      As a rule, single sentences should not be written or printed as paragraphs. An exception may be made of sentences of transition, indicating the relation between the parts of an exposition or argument.