Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value of Financial Instruments
Liabilities - long-term debt (carried at cost)	$ 293,765	$ 291,306
Carrying Value
Fair Value of Financial Instruments
Liabilities - long-term debt (carried at cost)	284,699	286,046
Fair Value
Fair Value of Financial Instruments
Liabilities - long-term debt (carried at cost)	293,765	291,306
Significant other observable inputs (Level 2) | Recurring
Fair Value of Financial Instruments
Liabilities - long-term debt (carried at cost)	$ 293,765	$ 291,306