STATEMENTS OF CONSOLIDATED STOCKHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement Of Stockholders Equity [Abstract]
Weighted average repurchase price (in dollars per share)	$ 81.94	$ 96.18	$ 100.28
Repurchase amount remaining	$ 93.1
Cash dividends declared (in dollars per share)	$ 2.68	$ 2.40	$ 2.20