Acquisitions and Dispositions of Businesses - Schedule of Consideration Transferred and Preliminary Value of Intangible Assets (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Apr. 25, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Assets acquired:
Goodwill		$ 15,612		$ 15,612		$ 8,414
Liabilities assumed:
Funds held on behalf of clients		7,940	$ 7,230	7,940	$ 7,230
2024 Acquisition
Consideration transferred:
Cash				3,624
Deferred and contingent consideration				19
Class A ordinary shares issued				5,882
Aggregate consideration transferred				9,525
Assets acquired:
Cash and cash equivalents		298		298
Receivables		353		353
Fiduciary assets		465		465
Goodwill		7,192		7,192
Other intangible assets:
Operating lease right-of-use assets		144		144
Current assets		9		9
Non-current assets		171		171
Total assets acquired		15,491		15,491
Liabilities assumed:
Accounts payable and accrued liabilities		315		315
Fiduciary liabilities		465		465
Current liabilities		234		234
Long-term debt		3,422		3,422
Non-current operating lease liabilities		128		128
Deferred tax liabilities		1,062		1,062
Non-current liabilities		147		147
Total liabilities assumed		5,773		5,773
Less: Fair value of redeemable noncontrolling interests		(108)		(108)
Less: Fair value of nonredeemable noncontrolling interests		(85)		(85)
Net assets acquired		9,525		9,525
Funds held on behalf of clients		315		315
2024 Acquisition | Customer-related and contract-based
Other intangible assets:
Intangible assets		6,032		6,032
2024 Acquisition | Tradenames
Other intangible assets:
Intangible assets		801		801
2024 Acquisition | Technology and other
Other intangible assets:
Intangible assets		26		26
NFP Acquisition
Consideration transferred:
Cash	$ 3,200			3,247
Deferred and contingent consideration				0
Class A ordinary shares issued				5,882
Aggregate consideration transferred	$ 9,100			9,129
Assets acquired:
Cash and cash equivalents		293		293
Receivables		325		325
Fiduciary assets		411		411
Goodwill		6,987		6,987
Other intangible assets:
Operating lease right-of-use assets		140		140
Current assets		3		3
Non-current assets		169		169
Total assets acquired		14,978		14,978
Liabilities assumed:
Accounts payable and accrued liabilities		283		283
Fiduciary liabilities		411		411
Current liabilities		232		232
Long-term debt		3,422		3,422
Non-current operating lease liabilities		125		125
Deferred tax liabilities		1,038		1,038
Non-current liabilities		145		145
Total liabilities assumed		5,656		5,656
Less: Fair value of redeemable noncontrolling interests		(108)		(108)
Less: Fair value of nonredeemable noncontrolling interests		(85)		(85)
Net assets acquired		9,129		9,129
NFP Acquisition | Customer-related and contract-based
Other intangible assets:
Intangible assets		5,825		5,825
NFP Acquisition | Tradenames
Other intangible assets:
Intangible assets		800		800
NFP Acquisition | Technology and other
Other intangible assets:
Intangible assets		25		25
Other Acquisitions
Consideration transferred:
Cash				377
Deferred and contingent consideration				19
Class A ordinary shares issued				0
Aggregate consideration transferred		280	$ 14	396	$ 23
Assets acquired:
Cash and cash equivalents		5		5
Receivables		28		28
Fiduciary assets		54		54
Goodwill		205		205
Other intangible assets:
Operating lease right-of-use assets		4		4
Current assets		6		6
Non-current assets		2		2
Total assets acquired		513		513
Liabilities assumed:
Accounts payable and accrued liabilities		32		32
Fiduciary liabilities		54		54
Current liabilities		2		2
Long-term debt		0		0
Non-current operating lease liabilities		3		3
Deferred tax liabilities		24		24
Non-current liabilities		2		2
Total liabilities assumed		117		117
Less: Fair value of redeemable noncontrolling interests		0		0
Less: Fair value of nonredeemable noncontrolling interests		0		0
Net assets acquired		396		396
Other Acquisitions | Customer-related and contract-based
Other intangible assets:
Intangible assets		207		207
Other Acquisitions | Tradenames
Other intangible assets:
Intangible assets		1		1
Other Acquisitions | Technology and other
Other intangible assets:
Intangible assets		$ 1		$ 1