Borrowing Arrangements - Amended and Restated Credit Facility (Details)		1 Months Ended	6 Months Ended		7 Months Ended	12 Months Ended	41 Months Ended
	Feb. 20, 2015 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Sep. 30, 2015	Sep. 30, 2016	Feb. 20, 2020
Debt Instrument [Line Items]
Debt repayment			$ 85,900,000	$ 212,100,000
Restated Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 400,000,000.0
Debt repayment		$ 15,000,000
Senior credit facility, net of discount
Debt Instrument [Line Items]
Borrowings excluding debt discount		123,800,000	123,800,000
Senior credit facility, net of discount | Restated Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity	200,000,000.00
Current borrowing capacity		143,400,000	143,400,000
Letters of credit outstanding		56,600,000	56,600,000
Discount on debt		500,000	500,000
Deferred financing cost			700,000
Letter of credit facility | Restated Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity	100,000,000.00
Swingline Loans | Restated Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity	20,000,000.0
Term loan facility | Restated Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity	200,000,000.0
Year one amortization of principal	15,000,000
Year two amortization of principal	15,000,000
Year three amortization of principal	20,000,000
Year four amortization of principal	20,000,000
Year five amortization of principal	20,000,000
Year six amortization of principal	110,000,000
Revolving credit facility | Restated Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 100,000,000.0
LIBOR Loans | Senior credit facility, net of discount | Restated Credit Agreement
Debt Instrument [Line Items]
Period of total debt to EBITDA ratio	12 months
Base rate loans | Senior credit facility, net of discount | Restated Credit Agreement | Federal funds
Debt Instrument [Line Items]
Interest rate margin on variable rate basis	0.50%
Base rate loans | Senior credit facility, net of discount | Restated Credit Agreement | LIBOR
Debt Instrument [Line Items]
Interest rate margin on variable rate basis	1.00%
Credit Agreement | Senior credit facility, net of discount | Restated Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 143,370,000.00	$ 143,370,000.00
Maximum | Senior credit facility, net of discount | Restated Credit Agreement
Debt Instrument [Line Items]
Total debt to EBITDA ratio that is required to be maintained					4.0	3.75
Minimum | Senior credit facility, net of discount | Restated Credit Agreement
Debt Instrument [Line Items]
Fixed charge coverage ratio that is required to be maintained	1.25
Forecast | Maximum | Senior credit facility, net of discount | Restated Credit Agreement
Debt Instrument [Line Items]
Total debt to EBITDA ratio that is required to be maintained							3.5