Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Additional Information (Detail)

v3.10.0.1
Fair Value Measurements - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]        
Carrying value of notes $ 245,000,000   $ 245,000,000  
Debt instrument, estimated fair value 221,100,000   221,100,000  
Gain (Loss) on disposition of assets $ 759,000 $ (95,000) (4,400,000) $ 410,000
KGBIFM [Member]        
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]        
Gain (Loss) on disposition of assets     $ (4,800,000)