Credit Agreement - Narrative (Details)	Feb. 26, 2016 USD ($)	Aug. 09, 2017 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)
Line of Credit Facility [Line Items]
Borrowings under credit agreement			$ 140,000,000	$ 140,000,000
Credit Agreement | Line of Credit
Line of Credit Facility [Line Items]
Principal amount	$ 250,000,000.0
Borrowings under credit agreement			$ 140,000,000
Margin rate (as a percent)	0.50%
Effective interest rate (as a percent)	2.73%
Maximum leverage ratio			3.0
Minimum interest coverage ratio			3.0
Federal Funds Effective Rate | Credit Agreement | Line of Credit
Line of Credit Facility [Line Items]
Variable rate spread (as a percent)	0.50%
Adjusted LIBOR | Credit Agreement | Line of Credit
Line of Credit Facility [Line Items]
Variable rate spread (as a percent)	1.00%
Margin rate (as a percent)	1.50%
Minimum | Credit Agreement | Line of Credit
Line of Credit Facility [Line Items]
Commitment fee percentage (as a percent)	0.20%
Maximum | Credit Agreement | Line of Credit
Line of Credit Facility [Line Items]
Commitment fee percentage (as a percent)	0.30%
Subsequent Event [Member] | Credit Agreement | Line of Credit
Line of Credit Facility [Line Items]
Principal amount		$ 350,000,000.0