Any domestic life insurance company may accumulate and maintain, in addition to the net value of its policies and all accumulations held on account of existing or future dividends, policies, or groups of such policies, a contingency reserve of not more than twenty percent of said net value, or the sum of one hundred thousand dollars, whichever is the greater. For cause shown, the Department of Insurance may, at any time, and from time to time, permit any company to accumulate and maintain a larger contingency reserve, not exceeding one year under any one permission, by filing in the office of the department a written request stating the reasons therefor.