Long-Term Debt (Details 4) $ in Thousands	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Scheduled principal payments in the next twelve months	$ 605,525
Scheduled principal payments, year two	65,500
Scheduled principal payments, year three	5,500
Scheduled principal payments, year four	646,625
Scheduled principal payments, year five	400,000
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal after Year Five	1,200,000
Long term debt and capital lease obligations excluding discount and deferred costs	$ 2,923,150