Redeemable Noncontrolling Interest - Schedule of Ownership (Details) - AON LLC	9 Months Ended
	Sep. 30, 2024 shares
Equity, Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance (in units)	41,439,847
Issuances (in units)	2,122,132
Repurchases (in units)	(126,728)
Redemptions (in units)	0
Total Units Issued (in units)	43,435,251
Ending balance (in units)	43,435,251
Allocation of income to controlling and noncontrolling interests (in percent)	1
Allocation of losses to controlling and noncontrolling interests (in percent)	1
AON Inc.
Equity, Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance (in units)	13,330,051
Issuances (in units)	2,122,132
Repurchases (in units)	(126,728)
Redemptions (in units)	4,664,428
Total Units Issued (in units)	19,989,883
Ending balance (in units)	19,989,883
Allocation of income to controlling and noncontrolling interests (in percent)	0.460
Allocation of losses to controlling and noncontrolling interests (in percent)	0.363
Legacy AON Shareholders
Equity, Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance (in units)	28,109,796
Issuances (in units)	0
Repurchases (in units)	0
Redemptions (in units)	(4,664,428)
Total Units Issued (in units)	23,445,368
Ending balance (in units)	23,445,368
Allocation of income to controlling and noncontrolling interests (in percent)	0.540
Allocation of losses to controlling and noncontrolling interests (in percent)	0.637