Fair Value Measurement - Fair Value of Assets (Liabilities) Not Measured at Fair Value In Consolidated Balance Sheets (Details) - Fixed-Rate Long-Term Debt - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long term debt, fair value	$ 0	$ 0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long term debt, fair value	(124,590)	(183,765)
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long term debt, fair value	$ 0	$ 0