Consolidated Statements of Changes in Equity (unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Statement of Stockholders' Equity [Abstract]
Dividends declared, per share (in USD per share)	$ 0.26	$ 0.2575
Common stock, par value (in USD per share)	$ 2	$ 2	$ 2