CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Assets
Cash and cash equivalents	$ 1,066	$ 1,154
Accounts receivable, net of allowance of $2 at March 31, 2021 and December 31, 2020	511	583
Materials and supplies, net of allowance of $144 and $143 at March 31, 2021 and December 31, 2020, respectively	433	434
Restricted cash and cash equivalents	388	406
Other current assets	161	163
Total current assets	2,559	2,740
Property and equipment	23,020	23,040
Less accumulated depreciation	(5,541)	(5,373)
Property and equipment, net	17,479	17,667
Contract intangible assets	337	393
Deferred income taxes, net	11	9
Other assets	974	995
Total assets	21,360	21,804
Liabilities and equity
Accounts payable	189	194
Accrued income taxes	29	28
Debt due within one year	524	505
Other current liabilities	561	659
Total current liabilities	1,303	1,386
Long-term debt	7,096	7,302
Deferred income taxes, net	319	315
Other long-term liabilities	1,302	1,366
Total long-term liabilities	8,717	8,983
Commitments and contingencies
Shares, CHF 0.10 par value, 824,650,668 authorized, 142,363,647 conditionally authorized, 639,676,165 issued and 617,288,705 outstanding at March 31, 2021, and 824,650,660 authorized, 142,363,647 conditionally authorized, 639,676,165 issued and 615,140,276 outstanding at December 31, 2020	60	60
Additional paid-in capital	13,508	13,501
Accumulated deficit	(1,965)	(1,866)
Accumulated other comprehensive loss	(267)	(263)
Total controlling interest shareholders' equity	11,336	11,432
Noncontrolling interest	4	3
Total equity	11,340	11,435
Total liabilities and equity	$ 21,360	$ 21,804