Fair Value Measurements - The carrying value and fair value of financial instruments (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Financial assets:
Mortgage loans	$ 827	$ 791
Long-term debt	1,476	1,475
Level 1
Financial assets:
Cash and cash equivalents	1,276	1,406
Mortgage loans	0	0
Total financial assets not accounted for at fair value	1,276	1,406
Long-term debt	0	0
Total financial liabilities not accounted for at fair value	0	0
Level 2
Financial assets:
Cash and cash equivalents	0	0
Mortgage loans	0	0
Total financial assets not accounted for at fair value	0	0
Long-term debt	1,261	1,273
Total financial liabilities not accounted for at fair value	1,261	1,273
Level 3
Financial assets:
Cash and cash equivalents	0	0
Mortgage loans	790	754
Total financial assets not accounted for at fair value	790	754
Long-term debt	3	3
Total financial liabilities not accounted for at fair value	3	3
Carrying Value
Financial assets:
Cash and cash equivalents	1,276	1,406
Mortgage loans	827	791
Total financial assets not accounted for at fair value	2,103	2,197
Long-term debt	1,476	1,475
Total financial liabilities not accounted for at fair value	1,476	1,475
Fair Value
Financial assets:
Cash and cash equivalents	1,276	1,406
Mortgage loans	790	754
Total financial assets not accounted for at fair value	2,066	2,160
Long-term debt	1,264	1,276
Total financial liabilities not accounted for at fair value	$ 1,264	$ 1,276