Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 20	$ 23
Other intangible assets, accumulated amortization	307	457
Service Concession Asset, Accumulated Depreciation	$ 0	$ 0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	1,200,000,000	1,200,000,000
Common stock, shares issued (in shares)	817,843,916	817,203,691
Common stock, shares outstanding (in shares)	663,952,656	662,298,096
Treasury stock, shares (in shares)	153,891,260	154,905,595
Variable Interest Entity [Line Items]
Non-recourse debt - current balance at variable interest entities	$ 1,868	$ 1,659
Non-recourse debt - noncurrent, balance at variable interest entities	14,914	13,986
Consolidated Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Non-recourse debt - current balance at variable interest entities	337	479
Non-recourse debt - noncurrent, balance at variable interest entities	$ 3,873	$ 2,922