Acquisitions and Dispositions of Businesses - Narrative (Details) - USD ($) shares in Millions, $ in Millions			3 Months Ended			6 Months Ended	9 Months Ended		101 Months Ended
	Jan. 01, 2025	Apr. 25, 2024	Sep. 30, 2025	Jun. 30, 2025	Sep. 30, 2024	Jun. 30, 2025	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Oct. 30, 2025	Sep. 03, 2025	Dec. 31, 2024	May 01, 2017
Business Combination [Line Items]
Decrease of goodwill							$ 27
Gain on disposition of business			$ 1		$ 76		1	$ 333
Disposal group, including discontinued operation, assets, current			1,274				1,274		$ 1,274			$ 1
Disposal group, including discontinued operation, liabilities, current			166				166		166			$ 0
Deferred consideration on divestiture					$ 2		$ 108	$ 84	$ 192
Held-for-sale | NFP Acquisition
Business Combination [Line Items]
Disposal group, not discontinued operation, impairment loss			$ 0
Disposal group, including discontinued operation, assets, current											$ 1,300
Disposal group, including discontinued operation, liabilities, current											166
Disposal group, including discontinued operation, intangible assets, current											754
Disposal group, including discontinued operation, goodwill, current											$ 389
Held-for-sale | NFP Acquisition | Subsequent Event
Business Combination [Line Items]
Purchase price										$ 2,300
Disposed of by Sale | May 1, 2017 Divested Business
Business Combination [Line Items]
Purchase price													$ 4,300
Deferred consideration													$ 500
Griffiths & Armour
Business Combination [Line Items]
Percentage of capital acquired	100.00%
Total consideration	$ 418
NFP Acquisition
Business Combination [Line Items]
Percentage of capital acquired		100.00%
Total consideration		$ 9,100				$ 9,129
Cash		$ 3,200				$ 3,247
Number of shares issued for acquisition (up to)		19
Equity interest issued or issuable, value		$ 5,900
Adjustments for cash and certain assumed liabilities		$ 3,900
Increase of intangible assets				$ 125
Decrease of deferred tax liabilities				110
Decrease of other noncurrent assets				61
Decrease of other current assets				28
Decrease of goodwill				$ 115