Maximize Americans' Retirement Security Act This bill revises the fiduciary duties for a retirement or employee benefit plan that is regulated under the Employee Retirement Income Security Act of 1974. The bill generally requires a fiduciary to select and maintain investments for a plan based solely on pecuniary factors. Under the bill, a pecuniary factor is a factor that is expected to have a material effect on the risk or return of an investment based on appropriate investment horizons that are consistent with the plan's investment objectives and funding policy. A fiduciary may only use nonpecuniary factors if the fiduciary is unable to distinguish between investment alternatives on the basis of pecuniary factors alone. In such a case, the fiduciary must provide specified documentation to the plan's participants and beneficiaries, including an explanation of how the chosen nonpecuniary factors are consistent with their interests.