Cannot implicilty convert type 'IList'

System.Collections.IList instrumentList = new List<Instrument>();

instrumentList = session.CreateCriteria<Financial>("f")
                                       .CreateCriteria("fa.InstrumentList", "il", NHibernate.SqlCommand.JoinType.InnerJoin)
                                        .SetResultTransformer(new NHibernate.Transform.DistinctRootEntityResultTransformer())
                                        .List<Instrument>();