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Employee Benefit Plans - Weighted-average Assumptions Used to Determine Benefit Obligations (Detail)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Pension Plan      
Discount rate used to determine pension expense :      
Discount rate 4.25% 4.75% 4.00%
Discount rate used to determine value of obligations      
Discount rate 4.55% 4.25% 4.75%
Long term rate of return 7.50% 7.50% 8.00%
Retirement Plan | La Barge      
Discount rate used to determine pension expense :      
Discount rate 3.70% 4.00% 3.10%
Discount rate used to determine value of obligations      
Discount rate 4.00% 3.70% 4.00%