Debt Instruments - Finance Leases (Details)	1 Months Ended	12 Months Ended
	Nov. 30, 2017 USD ($) property	Dec. 31, 2017	Sep. 30, 2018 USD ($)
Sale Leaseback Transaction [Line Items]
Sale leaseback transaction, amount due under financing arrangement			$ 65,900,000
Master Sale-Leaseback Agreement
Sale Leaseback Transaction [Line Items]
Sale leaseback transaction, number of properties sold and leased back at amount equal to the repurchase price (or more) | property	1
Sale leaseback transaction, total repurchase price			24,600,000
Sale leaseback transaction, maximum sales price of properties sold and leasing back	$ 75,000,000.0
Sale leaseback transaction, additional amount company may sell and lease back			$ 50,400,000
Minimum
Sale Leaseback Transaction [Line Items]
Sale leaseback transaction, expiration period		15 years
Maximum
Sale Leaseback Transaction [Line Items]
Sale leaseback transaction, expiration period		20 years
Sale leaseback transaction, renewal period (up to)		20 years