CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Allowance for doubtful accounts	$ 180	$ 171
Customers (net of allowance for doubtful accounts of $180 million and $171 million at respective dates) (includes $1.84 billion and $2.06 billion related to VIEs, net of allowance for doubtful accounts of $180 million and $171 million at respective dates)	2,080	2,345
Accrued unbilled revenue (includes $976 million and $1.09 billion related to VIEs at respective dates)	1,070	1,207
Long-term debt, classified as current (includes $32 million and $18 million related to VIEs at respective dates)	4,553	4,481
Long-term debt (includes $1.83 billion and $1.82 billion related to VIEs at respective dates)	$ 39,123	$ 38,225
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	3,600,000,000	3,600,000,000
Common stock, shares outstanding (in shares)	1,987,472,590	1,985,400,540
Treasury stock, shares at cost (in shares)	437,743,590	477,743,590
Variable Interest Entity, Primary Beneficiary
Allowance for doubtful accounts	$ 180	$ 171
Customers (net of allowance for doubtful accounts of $180 million and $171 million at respective dates) (includes $1.84 billion and $2.06 billion related to VIEs, net of allowance for doubtful accounts of $180 million and $171 million at respective dates)	1,840	2,060
Accrued unbilled revenue (includes $976 million and $1.09 billion related to VIEs at respective dates)	976	1,090
Net noncurrent accounts receivable	115	187
Noncurrent allowance for doubtful accounts	11	15
Long-term debt, classified as current (includes $32 million and $18 million related to VIEs at respective dates)	32	18
Long-term debt (includes $1.83 billion and $1.82 billion related to VIEs at respective dates)	$ 1,830	$ 1,820