Leases - Operating and Finance Lease Right of Use ("ROU") Assets and Lease Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Operating leases:
Operating lease ROU assets	$ 519	$ 552
Accrued expenses and other liabilities	145	152
Other non-current liabilities	460	491
Total operating lease liabilities	605	643
Finance leases:
Property and equipment, gross	96	98
Accumulated depreciation	(45)	(46)
Property and equipment, net	51	52
Short-term debt	23	18
Long-term debt	30	36
Total finance lease liabilities	$ 53	$ 54
Balance sheet location of current operating lease liabilities	Accrued expenses and other liabilities	Accrued expenses and other liabilities
Balance sheet location of non-current operating lease liabilities	Other non-current liabilities	Other non-current liabilities
Balance sheet location of non-current finance lease assets	Property and equipment	Property and equipment
Balance sheet location of current finance lease liabilities	Short-term debt	Short-term debt
Balance sheet location of non-current finance lease liabilities	Long-term debt	Long-term debt