Consolidated Balance Sheets (Parenthetical) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Accumulated depreciation	$ 11,512,000,000	$ 10,004,000,000
Amortized intangible assets, accumulated amortization	306	279
Amortized intangible liabilities, accumulated amortization	$ 1,043	$ 1,022