Corporate Investments and Funds Held For Clients (Available-For-Sale Securities That Have Been In An Unrealized Loss Position) (Details) - USD ($) $ in Millions	Dec. 31, 2019		Jun. 30, 2019
Debt Securities, Available-for-sale [Line Items]
Unrealized losses less than 12 months	$ (14.3)		$ (7.2)
Fair market value of securities in unrealized loss position less than 12 months	2,801.3		1,107.7
Unrealized losses greater than 12 months	(5.5)		(25.9)
Fair market value of securities in unrealized loss positions greater than 12 months	2,741.7		7,192.5
Total gross unrealized losses	(19.8)		(33.1)
Total fair market value	5,543.0		8,300.2
Fair market value	24,801.1	[1]	24,859.1	[2]
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Unrealized losses less than 12 months	(2.6)		(0.6)
Fair market value of securities in unrealized loss position less than 12 months	715.4		151.9
Unrealized losses greater than 12 months	(0.3)		(6.1)
Fair market value of securities in unrealized loss positions greater than 12 months	260.3		2,055.6
Total gross unrealized losses	(2.9)		(6.7)
Total fair market value	975.7		2,207.5
Fair market value	11,149.1		10,867.9
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Unrealized losses less than 12 months	(2.6)		(0.2)
Fair market value of securities in unrealized loss position less than 12 months	593.2		171.9
Unrealized losses greater than 12 months	(0.9)		(5.2)
Fair market value of securities in unrealized loss positions greater than 12 months	628.8		2,083.5
Total gross unrealized losses	(3.5)		(5.4)
Total fair market value	1,222.0		2,255.4
Fair market value	4,239.3		4,690.7
U.S. government agency securities
Debt Securities, Available-for-sale [Line Items]
Unrealized losses less than 12 months	(0.4)		0.0
Fair market value of securities in unrealized loss position less than 12 months	257.5		1.8
Unrealized losses greater than 12 months	(3.4)		(8.0)
Fair market value of securities in unrealized loss positions greater than 12 months	1,005.0		1,159.4
Total gross unrealized losses	(3.8)		(8.0)
Total fair market value	1,262.5		1,161.2
Fair market value	3,604.7		2,948.8
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Unrealized losses less than 12 months	(0.7)		0.0
Fair market value of securities in unrealized loss position less than 12 months	91.7		0.0
Unrealized losses greater than 12 months	(0.6)		(5.8)
Fair market value of securities in unrealized loss positions greater than 12 months	743.3		1,671.4
Total gross unrealized losses	(1.3)		(5.8)
Total fair market value	835.0		1,671.4
Fair market value	2,066.3		2,623.9
Canadian government obligations and Canadian government agency obligations
Debt Securities, Available-for-sale [Line Items]
Unrealized losses less than 12 months	(6.2)		(6.0)
Fair market value of securities in unrealized loss position less than 12 months	870.1		662.7
Unrealized losses greater than 12 months	0.0		0.0
Fair market value of securities in unrealized loss positions greater than 12 months	0.0		1.1
Total gross unrealized losses	(6.2)		(6.0)
Total fair market value	870.1		663.8
Fair market value	1,175.0		1,165.1
Canadian provincial bonds
Debt Securities, Available-for-sale [Line Items]
Unrealized losses less than 12 months	(0.6)		(0.3)
Fair market value of securities in unrealized loss position less than 12 months	113.8		81.5
Unrealized losses greater than 12 months	0.0		(0.2)
Fair market value of securities in unrealized loss positions greater than 12 months	30.5		50.1
Total gross unrealized losses	(0.6)		(0.5)
Total fair market value	144.3		131.6
Fair market value	733.4		814.2
Municipal bonds
Debt Securities, Available-for-sale [Line Items]
Unrealized losses less than 12 months	(0.1)		0.0
Fair market value of securities in unrealized loss position less than 12 months	19.0		1.5
Unrealized losses greater than 12 months	0.0		(0.1)
Fair market value of securities in unrealized loss positions greater than 12 months	6.6		23.3
Total gross unrealized losses	(0.1)		(0.1)
Total fair market value	25.6		24.8
Fair market value	605.8		612.4
Other securities
Debt Securities, Available-for-sale [Line Items]
Unrealized losses less than 12 months	(1.1)		(0.1)
Fair market value of securities in unrealized loss position less than 12 months	140.6		36.4
Unrealized losses greater than 12 months	(0.3)		(0.5)
Fair market value of securities in unrealized loss positions greater than 12 months	67.2		148.1
Total gross unrealized losses	(1.4)		(0.6)
Total fair market value	207.8		184.5
Fair market value	1,227.5		1,136.1
Fair Value, Inputs, Level 1
Debt Securities, Available-for-sale [Line Items]
Fair market value	0.0		0.0
Fair Value, Inputs, Level 3
Debt Securities, Available-for-sale [Line Items]
Fair market value	$ 0.0		$ 0.0

[1] Included within available-for-sale securities are corporate investments with fair values of $7.2 million and funds held for clients with fair values of $24,793.9 million. All available-for-sale securities were included in Level 2 of the fair value hierarchy.

[2] Included within available-for-sale securities are corporate investments with fair values of $271.9 million and funds held for clients with fair values of $24,587.2 million. All available-for-sale securities were included in Level 2 of the fair value hierarchy.