Fair Value Measurements - The carrying value and fair value of financial instruments (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Financial assets:
Mortgage loans	$ 692	$ 520
Long-term debt	1,542	1,964
Level 1
Financial assets:
Cash and cash equivalents	967	2,131
Mortgage loans	0	0
Total financial assets not accounted for at fair value	967	2,131
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	1,393	2,258
Total financial liabilities not accounted for at fair value	1,393	2,258
Level 3
Financial assets:
Cash and cash equivalents	0	0
Mortgage loans	650	533
Total financial assets not accounted for at fair value	650	533
Long-term debt	3	3
Total financial liabilities not accounted for at fair value	3	3
Carrying Value
Financial assets:
Cash and cash equivalents	967	2,131
Mortgage loans	692	520
Total financial assets not accounted for at fair value	1,659	2,651
Long-term debt	1,542	1,964
Total financial liabilities not accounted for at fair value	1,542	1,964
Fair Value
Financial assets:
Cash and cash equivalents	967	2,131
Mortgage loans	650	533
Total financial assets not accounted for at fair value	1,617	2,664
Long-term debt	1,396	2,261
Total financial liabilities not accounted for at fair value	$ 1,396	$ 2,261