Arthur J. Gallagher & Co. completed the offering of $750 million in 4.600% Senior Notes due 2027, $750 million in 4.850% Senior Notes due 2029, $500 million in 5.000% Senior Notes due 2032, $1.5 billion in 5.150% Senior Notes due 2035, and $1.5 billion in 5.550% Senior Notes due 2055, totaling $5.5 billion in notes issued.