Del. Code tit. 18 § 1310
An insurer may invest in preferred or guaranteed stocks or shares of any solvent institution existing under the laws of the United States or of Canada, or of any state or province thereof, if all of the prior obligations and prior preferred stocks, if any, of such institution at the date of acquisition of the investment by the insurer are eligible as investments under this chapter and are rated 1 or 2 by the SVO or if the net earnings of such institution available for its fixed charges during either of the last 2 years have been, and during each of the last 5 years have averaged, not less than 11/2 times the sum of its average annual fixed charges, if any, its average annual maximum contingent interest, if any, and its average annual preferred dividend requirements. For the purposes of this section such computation shall refer to the fiscal years immediately preceding the date of acquisition of the investment by the insurer, and the term "preferred dividend requirement" shall be deemed to mean cumulative or noncumulative dividends, whether paid or not.
18 Del. C. § 1310