Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Properties, accumulated depreciation	$ 11,823	$ 11,982
Common stock, par or stated value per share (in dollars per share)	$ 1.00	$ 1.00
Common stock, shares authorized (in shares)	1,350,000,000	1,350,000,000
Common stock, shares outstanding, net of treasury shares (in shares)	255,109,247	257,904,956