Statements of Consolidated Stockholders' Equity (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018
Statement of Stockholders' Equity [Abstract]
Weighted average repurchase price (in dollars per share)	$ 92.95	$ 95.00	$ 98.55	$ 108.07	$ 104.74	$ 104.50
Repurchase amount remaining	$ 108.9
Cash dividends declared (in dollars per share)		$ 0.60	$ 0.60	$ 0.55	$ 0.55	$ 0.55