CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Allowance for doubtful accounts	$ 171	$ 146
Customers (net of allowance for doubtful accounts of $171 million and $146 million at respective dates) (includes $2.06 billion and $1.63 billion related to VIEs, net of allowance for doubtful accounts of $171 million and $143 million at respective dates)	2,345	1,883
Accrued unbilled revenue (includes $1.09 billion and $959 million related to VIEs at respective dates)	1,207	1,083
Long-term debt, classified as current (includes $18 million and $0 related to VIEs at respective dates)	4,481	28
Long-term debt (includes $1.82 billion and $1.0 billion related to VIEs at respective dates)	$ 38,225	$ 37,288
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)	1,985,400,540	1,984,678,673
Treasury stock, shares at cost (in shares)	477,743,590	0
Variable Interest Entity, Primary Beneficiary
Allowance for doubtful accounts	$ 171	$ 143
Customers (net of allowance for doubtful accounts of $171 million and $146 million at respective dates) (includes $2.06 billion and $1.63 billion related to VIEs, net of allowance for doubtful accounts of $171 million and $143 million at respective dates)	2,060	1,630
Accrued unbilled revenue (includes $1.09 billion and $959 million related to VIEs at respective dates)	1,090	959
Net noncurrent accounts receivable	187,000	0
Noncurrent allowance for doubtful accounts	15,000	0
Long-term debt, classified as current (includes $18 million and $0 related to VIEs at respective dates)	18	0
Long-term debt (includes $1.82 billion and $1.0 billion related to VIEs at respective dates)	$ 1,820	$ 1,000