Quarterly report pursuant to Section 13 or 15(d)

Business Segment Information - Narrative (Details)

v3.10.0.1
Business Segment Information - Narrative (Details) - USD ($)
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2018
Jun. 30, 2018
Dec. 31, 2017
Segment Reporting Information [Line Items]      
Unallocated corporate expense $ 0 $ 0  
Customer Who Declared Bankruptcy      
Segment Reporting Information [Line Items]      
Unallocated corporate expense     $ 1,001,000