Fair Value Measurements - The carrying value and fair value of financial instruments (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Financial assets:
Mortgage loans	$ 645	$ 676
Long-term debt	1,474	1,496
Level 1
Financial assets:
Cash and cash equivalents	988	872
Mortgage loans	0	0
Total financial assets not accounted for at fair value	988	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	1,300	1,299
Total financial liabilities not accounted for at fair value	1,300	1,299
Level 3
Financial assets:
Cash and cash equivalents	0	0
Mortgage loans	592	626
Total financial assets not accounted for at fair value	592	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	988	872
Mortgage loans	645	676
Total financial assets not accounted for at fair value	1,633	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	988	872
Mortgage loans	592	626
Total financial assets not accounted for at fair value	1,580	1,498
Long-term debt	1,303	1,302
Total financial liabilities not accounted for at fair value	$ 1,303	$ 1,302