Quarterly report pursuant to Section 13 or 15(d)

Business Segments and Customer Information - Major Customers (Details)

v3.10.0.1
Business Segments and Customer Information - Major Customers (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Revenue, Major Customer [Line Items]        
Revenues $ 168,931 $ 174,164 $ 516,222 $ 565,318
U.S. Postal Service        
Revenue, Major Customer [Line Items]        
Revenues 43,031 43,833 130,151 136,261
U.S. Navy        
Revenue, Major Customer [Line Items]        
Revenues 37,013 38,895 115,294 143,421
U.S. Army        
Revenue, Major Customer [Line Items]        
Revenues 38,167 45,717 122,502 150,217
U.S. Air Force        
Revenue, Major Customer [Line Items]        
Revenues 4,822 2,967 12,046 5,807
Total - DoD        
Revenue, Major Customer [Line Items]        
Revenues 80,002 87,579 249,842 299,445
Commercial aviation        
Revenue, Major Customer [Line Items]        
Revenues 32,641 30,637 98,213 94,706
Other commercial        
Revenue, Major Customer [Line Items]        
Revenues 3,386 2,833 10,418 9,270
Total - Commercial        
Revenue, Major Customer [Line Items]        
Revenues 36,027 33,470 108,631 103,976
Other government        
Revenue, Major Customer [Line Items]        
Revenues $ 9,871 $ 9,282 $ 27,598 $ 25,636
Customer Concentration Risk | Sales Revenue, Net        
Revenue, Major Customer [Line Items]        
Percentage of revenue by customer 100.00% 100.00% 100.00% 100.00%
Customer Concentration Risk | Sales Revenue, Net | U.S. Postal Service        
Revenue, Major Customer [Line Items]        
Percentage of revenue by customer 25.50% 25.20% 25.20% 24.10%
Customer Concentration Risk | Sales Revenue, Net | U.S. Navy        
Revenue, Major Customer [Line Items]        
Percentage of revenue by customer 21.90% 22.30% 22.40% 25.40%
Customer Concentration Risk | Sales Revenue, Net | U.S. Army        
Revenue, Major Customer [Line Items]        
Percentage of revenue by customer 22.60% 26.30% 23.70% 26.60%
Customer Concentration Risk | Sales Revenue, Net | U.S. Air Force        
Revenue, Major Customer [Line Items]        
Percentage of revenue by customer 2.90% 1.70% 2.30% 1.00%
Customer Concentration Risk | Sales Revenue, Net | Total - DoD        
Revenue, Major Customer [Line Items]        
Percentage of revenue by customer 47.40% 50.30% 48.40% 53.00%
Customer Concentration Risk | Sales Revenue, Net | Commercial aviation        
Revenue, Major Customer [Line Items]        
Percentage of revenue by customer 19.30% 17.60% 19.00% 16.80%
Customer Concentration Risk | Sales Revenue, Net | Other commercial        
Revenue, Major Customer [Line Items]        
Percentage of revenue by customer 2.00% 1.60% 2.00% 1.60%
Customer Concentration Risk | Sales Revenue, Net | Total - Commercial        
Revenue, Major Customer [Line Items]        
Percentage of revenue by customer 21.30% 19.20% 21.00% 18.40%
Customer Concentration Risk | Sales Revenue, Net | Other government        
Revenue, Major Customer [Line Items]        
Percentage of revenue by customer 5.80% 5.30% 5.40% 4.50%