Long-term Debt (Details Textual) - USD ($) $ in Thousands		6 Months Ended
	Jan. 29, 2015	Jun. 30, 2018	Dec. 31, 2017	Dec. 10, 2015
Debt Instrument [Line Items]
Property Subject to or Available for Operating Lease, Net		$ 513,900	$ 524,100
Long-term Debt		537,663
Private Placement [Member]
Debt Instrument [Line Items]
Initial value of debt	$ 625,500
Debt extinguished	408,500
Proceeds from Issuance of Private Placement	$ 211,600
Private Placement [Member] | Class A-1 Notes [Member]
Debt Instrument [Line Items]
Fixed interest rate of the notes	2.98%
Long-term Debt		162,200	174,900
Private Placement [Member] | Class A-2 Notes [Member]
Debt Instrument [Line Items]
Fixed interest rate of the notes	4.06%
Long-term Debt		375,500	375,500
2015 Notes [Domain] | Private Placement [Member]
Debt Instrument [Line Items]
Restricted Cash and Cash Equivalents		16,600	16,600
Fair value of term loan		543,700	$ 556,600
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				$ 200,000
Line of Credit Facility, Remaining Borrowing Capacity		$ 200,000
Base interest rate on credit facility		1.45%