Derivative Financial Instruments - Schedule of Change in Fair Value of Derivative Instruments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Derivative
Recognized gains (losses) for derivatives	$ 220	$ 202	$ 79	$ 335
Recognized gains (losses) for hedged item	$ 0	$ 0	$ 3	$ 0
Derivative, Gain (Loss), Statement of Income or Comprehensive Income Flag	Benefits and other changes in policy reserves	Benefits and other changes in policy reserves	Benefits and other changes in policy reserves	Benefits and other changes in policy reserves
Fair Value Hedging
Derivative
Recognized gains (losses) for derivatives	$ 173	$ 308	$ 320	$ 452
Recognized gains (losses) for hedged item	1	0	(12)	0
Derivatives designated as hedging instruments
Derivative
Recognized gains (losses) for derivatives	0	0	(3)	0
Recognized gains (losses) for hedged item	0	0	3	0
Derivatives designated as hedging instruments \| Fair Value Hedging
Derivative
Recognized gains (losses) for derivatives	(1)	0	11	0
Recognized gains (losses) for hedged item	1	0	(12)	0
Derivatives not designated as hedging instruments
Derivative
Recognized gains (losses) for derivatives	220	202	82	335
Recognized gains (losses) for hedged item	0	0	0	0
Derivatives not designated as hedging instruments \| Fair Value Hedging
Derivative
Recognized gains (losses) for derivatives	174	308	309	452
Recognized gains (losses) for hedged item	0	0	0	0
Interest rate swaps \| Derivatives designated as hedging instruments
Derivative
Recognized gains (losses) for derivatives	0	0	0	0
Recognized gains (losses) for hedged item	0	0	0	0
Interest rate swaps \| Derivatives designated as hedging instruments \| Fair Value Hedging
Derivative
Recognized gains (losses) for derivatives	(1)	0	11	0
Recognized gains (losses) for hedged item	1	0	(12)	0
Interest rate swaps \| Derivatives not designated as hedging instruments
Derivative
Recognized gains (losses) for derivatives	(5)	114	64	9
Recognized gains (losses) for hedged item	0	0	0	0
Interest rate swaps \| Derivatives not designated as hedging instruments \| Fair Value Hedging
Derivative
Recognized gains (losses) for derivatives	0	0	0	0
Recognized gains (losses) for hedged item	0	0	0	0
Foreign currency swaps \| Derivatives designated as hedging instruments
Derivative
Recognized gains (losses) for derivatives			(3)	0
Recognized gains (losses) for hedged item			3	0
Foreign currency swaps \| Derivatives designated as hedging instruments \| Fair Value Hedging
Derivative
Recognized gains (losses) for derivatives			0	0
Recognized gains (losses) for hedged item			0	0
Foreign currency swaps \| Derivatives not designated as hedging instruments
Derivative
Recognized gains (losses) for derivatives	0	0	(4)	0
Recognized gains (losses) for hedged item	0	0	0	0
Foreign currency swaps \| Derivatives not designated as hedging instruments \| Fair Value Hedging
Derivative
Recognized gains (losses) for derivatives	0	0	0	0
Recognized gains (losses) for hedged item	0	0	0	0
Equity options \| Derivatives not designated as hedging instruments
Derivative
Recognized gains (losses) for derivatives	269	260	161	487
Recognized gains (losses) for hedged item	0	0	0	0
Equity options \| Derivatives not designated as hedging instruments \| Fair Value Hedging
Derivative
Recognized gains (losses) for derivatives	0	0	0	0
Recognized gains (losses) for hedged item	0	0	0	0
Futures contracts \| Derivatives not designated as hedging instruments
Derivative
Recognized gains (losses) for derivatives	12	7	26	18
Recognized gains (losses) for hedged item	0	0	0	0
Futures contracts \| Derivatives not designated as hedging instruments \| Fair Value Hedging
Derivative
Recognized gains (losses) for derivatives	0	0	0	0
Recognized gains (losses) for hedged item	0	0	0	0
Other derivative investments \| Derivatives not designated as hedging instruments
Derivative
Recognized gains (losses) for derivatives	1	(4)	(10)	1
Recognized gains (losses) for hedged item	0	0	0	0
Other derivative investments \| Derivatives not designated as hedging instruments \| Fair Value Hedging
Derivative
Recognized gains (losses) for derivatives	0	0	0	0
Recognized gains (losses) for hedged item	0	0	0	0
Other embedded derivatives \| Derivatives not designated as hedging instruments
Derivative
Recognized gains (losses) for derivatives	3	3	7	6
Recognized gains (losses) for hedged item	0	0	0	0
Other embedded derivatives \| Derivatives not designated as hedging instruments \| Fair Value Hedging
Derivative
Recognized gains (losses) for derivatives	0	0	0	0
Recognized gains (losses) for hedged item	0	0	0	0
Indexed annuities/IUL embedded derivatives increase (decrease) \| Derivatives not designated as hedging instruments
Derivative
Recognized gains (losses) for derivatives	0	0	0	0
Recognized gains (losses) for hedged item	0	0	0	0
Indexed annuities/IUL embedded derivatives increase (decrease) \| Derivatives not designated as hedging instruments \| Fair Value Hedging
Derivative
Recognized gains (losses) for derivatives	174	308	309	452
Recognized gains (losses) for hedged item	0	0	0	0
Reinsurance related embedded derivatives \| Derivatives not designated as hedging instruments
Derivative
Recognized gains (losses) for derivatives	(60)	(178)	(162)	(186)
Recognized gains (losses) for hedged item	0	0	0	0
Reinsurance related embedded derivatives \| Derivatives not designated as hedging instruments \| Fair Value Hedging
Derivative
Recognized gains (losses) for derivatives	0	0	0	0
Recognized gains (losses) for hedged item	$ 0	$ 0	$ 0	$ 0

Fidelity National Financial, Inc. 10-Q