Debt - Schedule of long-term debt outstanding (Details) - USD ($)	Mar. 31, 2019	Jun. 30, 2018
Debt Instrument [Line Items]
Total	$ 549,000,000	$ 545,700,000
Less: amounts due within one year	0	0
Long-term debt	$ 549,000,000	$ 545,700,000
Senior unsecured notes, 5.20% due July 2021
Debt Instrument [Line Items]
Interest rate	5.20%	5.20%
Face amount	$ 250,000,000.0	$ 250,000,000.0
Total	$ 249,700,000	$ 246,600,000
4.45% Senior Unsecured Notes due 2023
Debt Instrument [Line Items]
Interest rate	4.45%	4.45%
Face amount	$ 300,000,000.0	$ 300,000,000.0
Total	$ 299,300,000	$ 299,100,000

Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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