Investments (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Short-term investments:
Available-for-sale securities, current			$ 0
Total short-term investments	$ 482		44
Long-term investments:
Long-term Investments, Total	433		440
Cost Method Investments	3		4
Available-for-sale Securities, Gross Realized Gain (Loss)	0	$ 0
Long-term investments [Member]
Long-term investments:
Equity and Cost Method Investments	36		35
Restricted investments	397		405
Short-term Investments [Member]
Short-term investments:
Equity investment security	27		27
Held-to-maturity investment securities	27		14
Time Deposits	323		$ 3
Long-term investments:
Debt Securities, Available-for-sale, Amortized Cost	105
Available-for-sale securities, current	$ 105