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BUSINESS SEGMENTS - Schedule of Segment Revenue, Segment Expenses, and Segment Profits (Details) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2026 USD ($) | Jun. 30, 2025 USD ($) | Jun. 30, 2026 USD ($) segment | Jun. 30, 2025 USD ($)
Segment Reporting [Abstract] |  |  |  |  |
Number of reporting segments | segment |  |  |  | 4 |
Segment Reporting [Line Items] |  |  |  |  |
Revenue |  | $ 7,071 | $ 6,744 | $ 13,725 | $ 13,007
Depreciation, amortization, and other |  | 115 | 53 | 169 | 104
General and administrative | [1] | 220 | 210 | 439 | 419
OPERATING INCOME |  | 1,229 | 1,236 | 2,293 | 2,184
Total reportable segment revenue |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Revenue |  | 6,310 | 6,025 | 12,211 | 11,636
Total reportable segment revenue | U.S. & Canada |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Revenue |  | 5,263 | 4,962 | 10,218 | 9,660
Depreciation, amortization, and other |  | 90 | 27 | 114 | 54
General and administrative |  | 33 | 29 | 63 | 59
Other segment items (primarily non-operating income and expenses) |  | (2) | (2) | (2) | (3)
OPERATING INCOME |  | 770 | 786 | 1,416 | 1,430
Total reportable segment revenue | EMEA |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Revenue |  | 610 | 655 | 1,117 | 1,169
Depreciation, amortization, and other |  | 9 | 9 | 19 | 19
General and administrative |  | 25 | 26 | 52 | 51
Other segment items (primarily non-operating income and expenses) |  | (1) | (2) | (2) | 0
OPERATING INCOME |  | 144 | 157 | 216 | 231
Total reportable segment revenue | Greater China |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Revenue |  | 164 | 152 | 316 | 288
Depreciation, amortization, and other |  | 2 | 3 | 5 | 5
General and administrative |  | 13 | 12 | 25 | 24
Other segment items (primarily non-operating income and expenses) |  | 0 | 0 | (2) | (1)
OPERATING INCOME |  | 55 | 53 | 100 | 98
Total reportable segment revenue | APEC |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Revenue |  | 273 | 256 | 560 | 519
Depreciation, amortization, and other |  | 2 | 2 | 4 | 4
General and administrative |  | 15 | 15 | 31 | 29
Other segment items (primarily non-operating income and expenses) |  | (2) | (1) | 0 | 1
OPERATING INCOME |  | 69 | 76 | 140 | 156
Net fee revenues |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Gross fee revenues |  | 1,578 | 1,400 | 3,011 | 2,675
Contract investment amortization |  | (31) | (29) | (66) | (57)
Revenue |  | 1,547 | 1,371 | 2,945 | 2,618
Net fee revenues | Total reportable segment revenue | U.S. & Canada |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Gross fee revenues |  | 906 | 800 | 1,679 | 1,509
Contract investment amortization |  | (23) | (21) | (44) | (41)
Revenue |  | 883 | 779 | 1,635 | 1,468
Net fee revenues | Total reportable segment revenue | EMEA |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Gross fee revenues |  | 159 | 168 | 291 | 286
Contract investment amortization |  | (5) | (4) | (10) | (8)
Revenue |  | 154 | 164 | 281 | 278
Net fee revenues | Total reportable segment revenue | Greater China |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Gross fee revenues |  | 68 | 64 | 137 | 124
Contract investment amortization |  | 0 | 0 | (1) | 0
Revenue |  | 68 | 64 | 136 | 124
Net fee revenues | Total reportable segment revenue | APEC |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Gross fee revenues |  | 86 | 83 | 190 | 181
Contract investment amortization |  | (1) | (2) | (3) | (3)
Revenue |  | 85 | 81 | 187 | 178
Owned, leased, and other |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Revenue |  | 466 | 441 | 878 | 802
Operating costs | [1] | 417 | 363 | 794 | 695
Owned, leased, and other | Total reportable segment revenue | U.S. & Canada |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Revenue |  | 148 | 140 | 288 | 260
Operating costs |  | 131 | 107 | 252 | 217
Owned, leased, and other | Total reportable segment revenue | EMEA |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Revenue |  | 158 | 164 | 274 | 278
Operating costs |  | 135 | 142 | 255 | 257
Owned, leased, and other | Total reportable segment revenue | Greater China |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Revenue |  | 12 | 10 | 20 | 17
Operating costs |  | 10 | 7 | 20 | 15
Owned, leased, and other | Total reportable segment revenue | APEC |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Revenue |  | 47 | 43 | 86 | 78
Operating costs |  | 47 | 34 | 88 | 66
Reimbursements |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Revenue |  | 5,058 | 4,932 | 9,902 | 9,587
Operating costs |  | 5,100 | 4,874 | 10,036 | 9,596
Reimbursements | Total reportable segment revenue | U.S. & Canada |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Revenue |  | 4,232 | 4,043 | 8,295 | 7,932
Operating costs |  | 4,241 | 4,015 | 8,375 | 7,903
Reimbursements | Total reportable segment revenue | EMEA |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Revenue |  | 298 | 327 | 562 | 613
Operating costs |  | 298 | 323 | 577 | 611
Reimbursements | Total reportable segment revenue | Greater China |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Revenue |  | 84 | 78 | 160 | 147
Operating costs |  | 84 | 77 | 168 | 147
Reimbursements | Total reportable segment revenue | APEC |  |  |  |  |
Segment Reporting [Line Items] |  |  |  |  |
Revenue |  | 141 | 132 | 287 | 263
Operating costs |  | $ 142 | $ 130 | $ 297 | $ 263
[1] | The 2025 second quarter and 2025 first half reflect the reclassification of $35 million and $71 million, respectively, of other expenses previously reported under the “General, administrative, and other” caption to the “Owned, leased, and other expense” caption of our Income Statements to conform to our current presentation.

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