Leases - Balance Sheet Disclosure (Details) - USD ($) $ in Millions	Dec. 31, 2020		Dec. 31, 2019
Assets
Total lease assets	$ 922		$ 367
Liabilities
Total lease liabilities	$ 1,036	[1]	387
Accounts payable and accrued liabilities	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent
Long-term debt and finance lease obligations	us-gaap:OtherLiabilitiesNoncurrent
Current portion of long-term debt and finance lease obligations	us-gaap:DebtCurrent
Long-term debt and finance lease obligations	us-gaap:LongTermDebtAndCapitalLeaseObligations
Other assets
Assets
Operating lease assets	$ 895		344
Property and equipment, net
Assets
Finance lease assets	27		23
Accounts payable and accrued liabilities
Liabilities
Current operating lease liabilities	175		109
Other long-term liabilities
Liabilities
Noncurrent operating lease liabilities	832		251
Current portion of long-term debt and finance lease obligations
Liabilities
Current finance lease liabilities	8		7
Long-term debt and finance lease obligations
Liabilities
Noncurrent finance lease liabilities	$ 21		$ 20

[1] Lease payments recognized as part of lease liabilities for optional renewal periods are insignificant.