Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements - Schedule of Instruments Not Carried at Fair Value (Details)

v3.8.0.1
Fair Value Measurements - Schedule of Instruments Not Carried at Fair Value (Details) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Long term debt, including current portion:    
Carrying value $ 1,718,297 $ 1,698,778
Fair value $ 1,645,616 $ 1,716,385