We agree that the district court’s instructions on this issue did not limit the fortuity defense to those harms specifically expected or intended by the insured. As the London Insurers point out, the district court instructed the jury: “If you find that Koppers intentionally or knowingly caused property damage for which it seeks coverage, then Koppers may not recover for that specific damage.” App. at 1013. However, the court concluded this instruction by stating: “To lose coverage, Koppers must have intended the same general type of property damage that occurred.” Id. We think that the instructions on this point, when read as a whole, fairly conveyed to the jury what the parties agree is the correct legal standard. See Douglas v. Owens, 50 F.3d 1226, 1233 (3d Cir.1995); Savarese v. Agriss, 883 F.2d 1194, 1202 (3d Cir.1989).
C.
The London Insurers’ third claim is that the district court abused its discretion by excluding their proffered evidence of Koppers’ failure to mitigate the property damage. The insurers argue that, under Pennsylvania law, an insured has an ongoing duty to mitigate its losses, and that Koppers’ recovery must be reduced by the amount of loss which could have been prevented if Koppers had undertaken reasonable efforts to mitigate the property damage.
The district court ruled, as a general matter, that evidence of Koppers’ failure to mitigate damages would be admissible. Although the precise basis for the district court’s decision to exclude the London Insurers’ proffered evidence is not clear from the record, we find no reversible error.
As a matter of general contract law, the Pennsylvania Supreme Court has held that a plaintiffs duty to mitigate its damages arises upon the defendant’s breach of the contract. E.g., Bafile v. Borough of Muncy, 527 Pa. 25, 588 A.2d 462, 464 (1991). The superior court has applied this rule in the context of an insurance contract, holding that, upon the insurer’s breach by refusing to indemnify the insured, the insured has a duty to mitigate its damages. See Forest City Grant Liberty Assocs. v. Genro II, Inc., 438 Pa.Super. 553, 652 A.2d 948, 952 (1995) (holding that insurer, once found to be hable, need not reimburse insured for unnecessary roof repairs). Here, the defendant insurers breached by refusing to indemnify Koppers in the 1980s, but all of the proffered “mitigation” evidence concerned the prior two decades. Even assuming, however, that the Pennsylvania Supreme Court would require an insured to mitigate its damages prior to the insurer’s breach of contract, the district court’s exclusion of the proffered evidence was proper because the evidence was legally insufficient to make out a claim of failure to mitigate damages.
Mitigation is an affirmative defense, so the burden of proving a failure to mitigate is on the defendant. See Williams v. Masters, Mates and Pilots of Am., 384 Pa. 413, 120 A.2d 896, 901 (1956); Ecksel v. Orleans Constr. Co., 360 Pa.Super. 119, 519 A.2d 1021, 1028 (1987). To prove a failure to mitigate, a defendant must show: (1) what reasonable actions the plaintiff ought to have taken, (2) that those actions would have reduced the damages, and (3) the amount by which the damages would have been reduced. See, e.g., Ecksel, 519 A.2d at 1021 (finding defendant’s failure to mitigate defense unproven because defendant did not show how plaintiff could have mitigated damages or how damages were made worse by alleged inaction); State Pub. Sch. Bldg. Auth. v. W.M. Anderson Co., 49 Pa.Cmwlth. 420, 410 A.2d 1329 (1980) (affirming judgment for contractor where breaching school district failed to show that contractor’s work was unreasonable and avoidable); see also New Castle County v. Hartford Accident & Indem. Co., 685 F.Supp. 1321, 1332 (D.Del. 1988) (holding that, where insurance policy contained express mitigation provision, insurer must specify what further injury occurred as result of the insured’s lack of mitigation).
The London Insurers’ evidence would not have satisfied any of these three elements, as it merely purports to show that Koppers was aware of property damage in the 1960s and 1970s but failed to correct the problem until