Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 1	$ 1	$ 1	$ 1	$ 1	$ 1	$ 1
Common stock, authorized (in shares)	2,000,000,000	2,000,000,000	2,000,000,000	2,000,000,000	2,000,000,000	2,000,000,000	2,000,000,000
Common stock, issued (in shares)	683,494,944	683,494,944	683,494,944	683,494,944	683,494,944	683,494,944	683,494,944
Treasury stock, shares (in shares)	177,340,358	173,275,586	173,447,198	170,495,859	150,213,621	148,485,202	146,993,164