Acquisitions and Dispositions of Businesses - Schedule of Consideration Transferred and Preliminary Value of Intangible Assets (Details) - USD ($) $ in Millions		12 Months Ended
	Apr. 25, 2024	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Consideration transferred:
Aggregate consideration transferred		$ 9,600	$ 50
Assets acquired:
Goodwill		15,234	8,414	$ 8,292
Liabilities assumed:
Funds held on behalf of clients		7,247	$ 6,901	$ 6,386
2024 Acquisition
Consideration transferred:
Cash		3,714
Deferred, contingent, and other consideration		33
Class A ordinary shares issued		5,882
Aggregate consideration transferred		9,629
Assets acquired:
Cash and cash equivalents		311
Receivables		358
Fiduciary assets		463
Goodwill		7,125
Other intangible assets:
Operating lease right-of-use assets		142
Current assets		84
Non-current assets		90
Total assets acquired		15,613
Liabilities assumed:
Accounts payable and accrued liabilities		316
Fiduciary liabilities		463
Current liabilities		250
Long-term debt		3,422
Non-current operating lease liabilities		129
Deferred tax liabilities		1,057
Non-current liabilities		154
Total liabilities assumed		5,791
Less: Fair value of redeemable noncontrolling interests		(108)
Less: Fair value of nonredeemable noncontrolling interests		(85)
Net assets acquired		9,629
Funds held on behalf of clients		312
2024 Acquisition | Customer-related and contract-based
Other intangible assets:
Intangible assets		6,212
2024 Acquisition | Tradenames
Other intangible assets:
Intangible assets		801
2024 Acquisition | Technology and other
Other intangible assets:
Intangible assets		27
NFP Acquisition
Consideration transferred:
Cash	$ 3,200	3,247
Deferred, contingent, and other consideration		0
Class A ordinary shares issued		5,882
Aggregate consideration transferred	$ 9,100	9,129
Assets acquired:
Cash and cash equivalents		294
Receivables		328
Fiduciary assets		411
Goodwill		6,867
Other intangible assets:
Operating lease right-of-use assets		138
Current assets		82
Non-current assets		88
Total assets acquired		14,983
Liabilities assumed:
Accounts payable and accrued liabilities		283
Fiduciary liabilities		411
Current liabilities		242
Long-term debt		3,422
Non-current operating lease liabilities		125
Deferred tax liabilities		1,026
Non-current liabilities		152
Total liabilities assumed		5,661
Less: Fair value of redeemable noncontrolling interests		(108)
Less: Fair value of nonredeemable noncontrolling interests		(85)
Net assets acquired		9,129
NFP Acquisition | Customer-related and contract-based
Other intangible assets:
Intangible assets		5,950
NFP Acquisition | Tradenames
Other intangible assets:
Intangible assets		800
NFP Acquisition | Technology and other
Other intangible assets:
Intangible assets		25
Other Acquisitions
Consideration transferred:
Cash		467
Deferred, contingent, and other consideration		33
Class A ordinary shares issued		0
Aggregate consideration transferred		500
Assets acquired:
Cash and cash equivalents		17
Receivables		30
Fiduciary assets		52
Goodwill		258
Other intangible assets:
Operating lease right-of-use assets		4
Current assets		2
Non-current assets		2
Total assets acquired		630
Liabilities assumed:
Accounts payable and accrued liabilities		33
Fiduciary liabilities		52
Current liabilities		8
Long-term debt		0
Non-current operating lease liabilities		4
Deferred tax liabilities		31
Non-current liabilities		2
Total liabilities assumed		130
Less: Fair value of redeemable noncontrolling interests		0
Less: Fair value of nonredeemable noncontrolling interests		0
Net assets acquired		500
Other Acquisitions | Customer-related and contract-based
Other intangible assets:
Intangible assets		262
Other Acquisitions | Tradenames
Other intangible assets:
Intangible assets		1
Other Acquisitions | Technology and other
Other intangible assets:
Intangible assets		$ 2