Through the Social Security Act and related legislation, Congress has created a comprehensive national insurance system that provides benefits for retired workers, disabled workers, unemployed workers, and their families. See United States v. Lee , 455 U. S. 252 , and nn. 1, 7 (1982). Congress funds Social Security by taxing both employers and employees under FICA on the wages employees earn. See 26 U. S. C. §3101(a) (tax on employees); §3111(a) (tax on employers). Congress has defined “wages” broadly, to encompass “all remuneration for employment.” §3121(a) (2006 ed. and Supp. III). The term “employment” has a similarly broad reach, extending to “any service, of whatever nature, performed … by an employee for the person employing him.” §3121(b).