Bucksport Energy Asset Investment - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Restricted Cash and Cash Equivalents Items [Line Items]    
Restricted cash $ 2,603 $ 4,946
Ownership of steam and electricity produced 28.00%  
Obligation to purchase steam output 72.00%  
Jointly Owned Utility Plant | Intangibles and other assets    
Restricted Cash and Cash Equivalents Items [Line Items]    
Restricted cash   $ 2,300