Segment Information Our reportable segments reflect certain reclassifications of prior year amounts from our United States mechanical construction and facilities services segment to our United States industrial services segment due to changes in our internal reporting structure. We have the following reportable segments, which provide services associated with the design, integration, installation, start-up, operation and maintenance of various systems: (a) United States electrical construction and facilities services (involving systems for electrical power transmission and distribution; premises electrical and lighting systems; process instrumentation in the refining, chemical processing, food processing and mining industries; low-voltage systems, such as fire alarm, security and process control; voice and data communication; roadway and transit lighting; and fiber optic lines); (b) United States mechanical construction and facilities services (involving systems for heating, ventilation, air conditioning, refrigeration and clean-room process ventilation; fire protection; plumbing, process and high-purity piping; controls and filtration; water and wastewater treatment; central plant heating and cooling; cranes and rigging; millwrighting; and steel fabrication, erection and welding); (c) United States building services; (d) United States industrial services; and (e) United Kingdom building services. The United States building services and United Kingdom building services segments principally consist of those operations which provide a portfolio of services needed to support the operation and maintenance of customers facilities, including commercial and government site-based operations and maintenance; facility maintenance and services, including reception, security and catering services; outage services to utilities and industrial plants; military base operations support services; mobile mechanical maintenance and services; floor care and janitorial services; landscaping, lot sweeping and snow removal; facilities management; vendor management; call center services; installation and support for building systems; program development, management and maintenance for energy systems; technical consulting and diagnostic services; infrastructure and building projects for federal, state and local governmental agencies and bodies; and small modification and retrofit projects, which services are not generally related to customers construction programs. The United States industrial services segment principally consists of those operations which provide industrial maintenance and services, including those for refineries and petrochemical plants, including on-site repairs, maintenance and service of heat exchangers, towers, vessels and piping; design, manufacturing, repair and hydro blast cleaning of shell and tube heat exchangers and related equipment; refinery turnaround planning and engineering services; specialty welding services; overhaul and maintenance of critical process units in refineries and petrochemical plants; and specialty technical services for refineries and petrochemical plants. The following tables present information about industry segments and geographic areas for the three months ended March 31, 2019 and 2018 (in thousands): For the three months ended March 31, 2019 2018 Revenues from unrelated entities: United States electrical construction and facilities services $ 528,070 $ 454,752 United States mechanical construction and facilities services 752,409 684,750 United States building services 512,079 454,752 United States industrial services 258,645 199,244 Total United States operations 2,051,203 1,793,498 United Kingdom building services 107,525 106,890 Total worldwide operations $ 2,158,728 $ 1,900,388 Total revenues: United States electrical construction and facilities services $ 528,982 $ 457,169 United States mechanical construction and facilities services 759,764 691,783 United States building services 530,596 470,099 United States industrial services 259,275 199,817 Less intersegment revenues (27,414 ) (25,370 ) Total United States operations 2,051,203 1,793,498 United Kingdom building services 107,525 106,890 Total worldwide operations $ 2,158,728 $ 1,900,388 For the three months ended March 31, 2019 2018 Operating income (loss): United States electrical construction and facilities services $ 42,951 $ 35,851 United States mechanical construction and facilities services 40,985 39,620 United States building services 27,483 17,077 United States industrial services 9,636 3,441 Total United States operations 121,055 95,989 United Kingdom building services 4,141 3,770 Corporate administration (22,611 ) (21,665 ) Restructuring expenses (275 ) (90 ) Total worldwide operations 102,310 78,004 Other corporate items: Net periodic pension (cost) income 406 737 Interest expense, net (2,823 ) (2,452 ) Income from continuing operations before income taxes $ 99,893 $ 76,289 March 31, 2019 December 31, 2018 Total assets: United States electrical construction and facilities services $ 737,743 $ 702,112 United States mechanical construction and facilities services 1,180,531 1,080,829 United States building services 975,444 846,221 United States industrial services 875,698 864,622 Total United States operations 3,769,416 3,493,784 United Kingdom building services 167,500 146,379 Corporate administration 341,408 448,644 Total worldwide operations $ 4,278,324 $ 4,088,807