The debt was issued when rates were very low with fixed coupons as low as 0.375%, only the more recently issued bonds are in the 3-4% range. Nevertheless they

The debt was issued when rates were very low with fixed coupons as low as 0.375%, only the more recently issued bonds are in the 3-4% range. Nevertheless they are paying fixed rates on their debt and (are likely) recieving floating rates on their cash.