Fair Value Measurements - The carrying value and fair value of financial instruments (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Financial assets:
Mortgage loans	$ 644	$ 676
Long-term debt	1,474	1,496
Level 1
Financial assets:
Cash and cash equivalents	1,221	872
Mortgage loans	0	0
Total financial assets not accounted for at fair value	1,221	872
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	1,210	1,299
Total financial liabilities not accounted for at fair value	1,210	1,299
Level 3
Financial assets:
Cash and cash equivalents	0	0
Mortgage loans	590	626
Total financial assets not accounted for at fair value	590	626
Long-term debt	3	3
Total financial liabilities not accounted for at fair value	3	3
Carrying Value
Financial assets:
Cash and cash equivalents	1,221	872
Mortgage loans	644	676
Total financial assets not accounted for at fair value	1,865	1,548
Long-term debt	1,474	1,496
Total financial liabilities not accounted for at fair value	1,474	1,496
Fair Value
Financial assets:
Cash and cash equivalents	1,221	872
Mortgage loans	590	626
Total financial assets not accounted for at fair value	1,811	1,498
Long-term debt	1,213	1,302
Total financial liabilities not accounted for at fair value	$ 1,213	$ 1,302