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Summary of Significant Accounting Policies (Tables)
 3 Months Ended
Mar. 31, 2021
Accounting Policies [Abstract]  
Schedule of marketable securities
The aggregate carrying values of our short-term and long-term investment securities consisted of the following at March 31, 2021 and December 31, 2020 (in millions):
March 31, 2021December 31, 2020
Available-for-sale securities
Time deposits$860 $1,130 
Debt securities7 7 
Total available-for-sale securities867 1,137 
Total investment securities$867 $1,137