CONSOLIDATED BALANCE SHEET (Parenthetical) - USD ($) shares in Thousands, $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Receivables, allowances	$ 1	$ 1
Property and equipment, accumulated depreciation	$ 3,437	$ 3,376
Common shares, par value	$ 1.25	$ 1.25
Common shares, authorized	1,360,000	1,360,000
Common shares, issued	744,905	746,391
Common shares, outstanding	744,905	746,391