Stock-Based Compensation - Additional Disclosures (Details) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017	Jul. 26, 2018	Apr. 30, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from issuances of shares of common stock			$ 10,864,000
Payments related to tax withholding			$ 14,477,000
Common stock reserved for future issuance or settlement (in shares)		9,700,000	9,700,000
Allocated Share-based Compensation Expense			$ 27,573,000
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in dollars per share)			$ 114.72	$ 64.32	$ 46.59
Total fair value of shares vested from RSU grants			$ 39,900,000	$ 23,000,000.0	$ 16,600,000
Total unrecognized compensation cost		$ 26,200,000	$ 26,200,000
Total unrecognized compensation cost, period of recognition			2 years 5 months 8 days
Granted (in shares)			645,146
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period			80,764
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation cost		$ 8,400,000	$ 8,400,000
Total unrecognized compensation cost, period of recognition			2 years 5 months 19 days
Granted (in dollars per share)			$ 113.88	$ 64.30	$ 46.31
Total intrinsic value of options exercised			$ 18,200,000	$ 15,100,000	$ 7,900,000
Proceeds from issuances of shares of common stock			10,900,000	13,500,000	9,300,000
Payments related to tax withholding			$ 14,700,000	$ 8,100,000	$ 5,800,000
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)			382,373
Allocated Share-based Compensation Expense			$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	60,680
2010 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance or settlement (in shares)		1,945,234	1,945,234
Maximum number of shares authorized (in shares)							7,000,000
2018 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance or settlement (in shares)		236,961	236,961
Maximum number of shares authorized (in shares)						250,000
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent		85.00%
Stock Issued During Period, Shares, Employee Stock Ownership Plan		13,039
Stock Issued During Period, Value, Employee Stock Purchase Plan		$ 900,000