Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurement - Fair Value and Carrying Value of Long-term Debt (Details)

v3.19.1
Fair Value Measurement - Fair Value and Carrying Value of Long-term Debt (Details) - USD ($)
Mar. 31, 2019
Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Long-term debt value (Level 2), Fair Value $ 219,678,000 $ 211,823,000
Long-term debt value (Level 2), Carrying Value 219,408,000 212,687,000
Fair Value, Measurements, Nonrecurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Assets, fair value disclosure, nonrecurring $ 0 $ 0