Subsequent Events (Details)	3 Months Ended
	Sep. 30, 2018 USD ($)	Aug. 01, 2018 branch	Jul. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Sep. 23, 2016 USD ($)	Aug. 09, 2016 USD ($)
Scenario, Forecast | Subsequent Event
Subsequent Event [Line Items]
Non-cash amortization related to deferred financing costs	$ 35,800,000
Prepayment premium related to redemption of notes	$ 23,700,000
Revolving Credit Facility | Line of Credit
Subsequent Event [Line Items]
Maximum borrowing capacity				$ 250,000,000.0	$ 300,000,000.0	$ 75,000,000.0
Revolving Credit Facility | Line of Credit | Subsequent Event
Subsequent Event [Line Items]
Maximum borrowing capacity			$ 450,000,000.0
Ciesco | Pennsylvania and Virginia | Subsequent Event
Subsequent Event [Line Items]
Number of branch locations | branch		6