Condensed Consolidated Statements of Stockholders’ Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)
Balance (in shares) at Jun. 30, 2018		154.5
Balance at Jun. 30, 2018	$ 1,094.3	$ 1.6	$ 1,048.5	$ 1,727.0	$ (1,630.8)	$ (51.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	110.9			126.6		(15.7)
Stock option exercises	19.6		19.6
Stock-based compensation	29.4		29.4
Treasury stock acquired	(120.3)				(120.3)
Treasury stock reissued	0.0		9.6		9.6
Common stock dividends	(112.6)			(112.6)
Balance (in shares) at Dec. 31, 2018		154.5
Balance at Dec. 31, 2018	$ 1,122.6	$ 1.6	1,087.8	1,843.8	(1,741.4)	(69.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury stock acquired (less than) (in shares)	1.1
Treasury stock reissued (in shares)	0.5
Common stock dividends (in dollars per share)	$ 0.97
Balance (in shares) at Sep. 30, 2018		154.5
Balance at Sep. 30, 2018	$ 1,234.0	$ 1.6	1,069.1	1,850.0	(1,623.2)	(63.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	44.2			49.9		(5.7)
Stock option exercises	1.0		1.0
Stock-based compensation	18.7		18.7
Treasury stock acquired	(119.2)				(119.2)
Treasury stock reissued	0.0		1.0		1.0
Common stock dividends	(56.1)			(56.1)
Balance (in shares) at Dec. 31, 2018		154.5
Balance at Dec. 31, 2018	$ 1,122.6	$ 1.6	1,087.8	1,843.8	(1,741.4)	(69.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury stock acquired (less than) (in shares)	1.1
Treasury stock reissued (in shares)	0.1
Common stock dividends (in dollars per share)	$ 0.485
Balance (in shares) at Jun. 30, 2019	154.5	154.5
Balance at Jun. 30, 2019	$ 1,127.5	$ 1.6	1,109.3	2,087.7	(1,999.8)	(71.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	69.5			66.0		3.5
Stock option exercises	21.9		21.9
Stock-based compensation	30.1		30.1
Treasury stock acquired	0.0				0.0
Treasury stock reissued	0.0		11.1		11.1
Common stock dividends	$ (123.8)			(123.8)
Balance (in shares) at Dec. 31, 2019	154.5	154.5
Balance at Dec. 31, 2019	$ 1,125.4	$ 1.6	1,150.1	2,030.1	(1,988.7)	(67.7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury stock acquired (less than) (in shares)	0.1
Treasury stock reissued (in shares)	0.5
Common stock dividends (in dollars per share)	$ 1.08
Balance (in shares) at Sep. 30, 2019		154.5
Balance at Sep. 30, 2019	$ 1,143.4	$ 1.6	1,131.1	2,082.0	(1,991.6)	(79.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	21.9			10.1		11.8
Stock option exercises	3.7		3.7
Stock-based compensation	18.4		18.4
Treasury stock acquired	0.0				0.0
Treasury stock reissued	0.0		2.9		2.9
Common stock dividends	$ (62.0)			(62.0)
Balance (in shares) at Dec. 31, 2019	154.5	154.5
Balance at Dec. 31, 2019	$ 1,125.4	$ 1.6	$ 1,150.1	$ 2,030.1	$ (1,988.7)	$ (67.7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury stock acquired (less than) (in shares)	0.1
Treasury stock reissued (in shares)	0.1
Common stock dividends (in dollars per share)	$ 0.54