Debt - Additional Information (Details)		12 Months Ended
	Jul. 01, 2025 USD ($)	Dec. 31, 2025 USD ($) extension_option	Dec. 31, 2024 USD ($)
Debt Instrument [Line Items]
Decrease in commercial paper		$ 113,000,000
Activity-based common stock ownership percentage		0.041
FHLB stock		$ 32,500,000	$ 34,500,000
Short-term debt, face amount		306,000,000
Estimate of Fair Value Measurement | Asset Pledged as Collateral
Debt Instrument [Line Items]
Fair value of pledged assets		1,400,000,000
FHLB borrowings
Debt Instrument [Line Items]
Short-term debt, face amount		0	0
Private Placement
Debt Instrument [Line Items]
Purchase price of sale of securities	$ 500,000,000
Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity		1,000,000,000
Potential maximum borrowing capacity		$ 1,250,000,000
Number of extension options | extension_option		2
Extension term		1 year
Junior Subordinated Debentures Due 2056
Debt Instrument [Line Items]
Interest rate		4.25%
Senior Notes
Debt Instrument [Line Items]
Optional redemption, period from issuance date		5 years
Senior Notes | Senior Notes Due 2055
Debt Instrument [Line Items]
Interest rate	6.58%
Facility agreement term	30 years
Amount of debt	$ 500,000,000
Semi-annual facility fee	1.789%
Stockholders' equity (excluding AOCI) threshold, triggering exercise of Issuance Right	$ 1,850,000,000
FHLB borrowings
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 730,000,000
Long-term line of credit		$ 437,000,000	$ 372,000,000