Retirement Plans and Benefits (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Multiemployer Plans [Line Items]      
Contributions $ 1,337 $ 8,255 $ 1,674
Boilermaker-Blacksmith National Pension Trust      
Multiemployer Plans [Line Items]      
EIN/PN 48-6168020/ 001    
PPA Zone Status Yellow    
Plan Year End for Zone Status Dec. 31, 2015    
Subject to Funding Improvement/ Rehabilitation Plan Implemented    
Contributions $ 208 1,009 380
Sur-charge Impose No    
Expiration Date of Collective Bargaining Agreement Oct. 31, 2017    
Pennsylvania Heavy and Highway Contractors Pension Trust      
Multiemployer Plans [Line Items]      
EIN/PN 23-6531755/ 001    
PPA Zone Status Green    
Plan Year End for Zone Status Dec. 31, 2014    
Subject to Funding Improvement/ Rehabilitation Plan No    
Contributions $ 1,086 7,210 1,171
Sur-charge Impose No    
Expiration Date of Collective Bargaining Agreement May 31, 2016    
Other Funds      
Multiemployer Plans [Line Items]      
Contributions $ 43 $ 36 $ 123