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Stockholders' Equity - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
 1 Months Ended 12 Months Ended
Dec. 18, 2014
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Class of Stock [Line Items]        
Common Stock, Shares Authorized   200,000,000us-gaap_CommonStockSharesAuthorized 200,000,000us-gaap_CommonStockSharesAuthorized  
The number of authorized shares of common stock, par value   $ 0.01us-gaap_CommonStockParOrStatedValuePerShare $ 0.01us-gaap_CommonStockParOrStatedValuePerShare  
Business Acquisition Stockholders Rights Plan Exercise Description   The rights will be exercisable only if a person or a group acquires or announces a tender or exchange offer to acquire 20% or more of our common stock or if we enter into other business combination transactions not approved by our board of directors.    
Business Acquisition Stockholders Rights Plan Expire Date   Dec. 28, 2015    
Business Acquisition Stockholders Rights Plan Redeemable Per Stock   $ 0wnc_BusinessAcquisitionStockholdersRightsPlanRedeemablePerStock    
Stock Repurchased During Period, Value $ 60us-gaap_StockRepurchasedDuringPeriodValue      
Series D Junior Participating Preferred Stock        
Class of Stock [Line Items]        
Preferred Stock, Par or Stated Value Per Share   $ 0us-gaap_PreferredStockParOrStatedValuePerShare
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesDPreferredStockMember		    
Stock Repurchased During Period, Shares   0us-gaap_StockRepurchasedDuringPeriodShares
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesDPreferredStockMember		    
Business Acquisition, Share Price   $ 0us-gaap_BusinessAcquisitionSharePrice
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesDPreferredStockMember		    
Preferred stock, shares issued     0us-gaap_PreferredStockSharesIssued
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesDPreferredStockMember		 0us-gaap_PreferredStockSharesIssued
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesDPreferredStockMember
Preferred Stock, Shares Outstanding     0us-gaap_PreferredStockSharesOutstanding
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesDPreferredStockMember		 0us-gaap_PreferredStockSharesOutstanding
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesDPreferredStockMember
Unclassified Preferred Stock        
Class of Stock [Line Items]        
Preferred Stock, Shares Authorized   25,000,000us-gaap_PreferredStockSharesAuthorized
/ us-gaap_StatementClassOfStockAxis
= us-gaap_PreferredClassAMember