Acquisitions and Divestitures - Acquisition-Related Costs (Detail) (General and Administrative Expense, USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
General and Administrative Expense
     
Business Acquisition [Line Items]      
Business Combination, Acquisition Related Costs $ 4,363 $ 6,729 $ 4,135