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Summary of Significant Accounting Policies (Narrative) (Details) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Special charges, net $ 20,008,000bid_SpecialCharges $ 1,372,000bid_SpecialCharges $ 0bid_SpecialCharges
Noncontrolling ownership interest percentage 80.00%us-gaap_MinorityInterestOwnershipPercentageByParent    
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners 20.00%us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners    
Allowance for doubtful accounts receivable 7,300,000us-gaap_AllowanceForDoubtfulAccountsReceivable 6,800,000us-gaap_AllowanceForDoubtfulAccountsReceivable  
Goodwill 14,000,000us-gaap_Goodwill 14,500,000us-gaap_Goodwill  
Accumulated amortization related to other intangible assets $ 6,100,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization $ 6,500,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization  
Building [Member]      
Fixed assets useful life 50 years    
Building Improvements [Member]      
Fixed assets useful life 20 years    
Furniture and Fixtures [Member]      
Fixed assets useful life 7 years    
Enterprise Systems [Member]      
Fixed assets useful life 10 years    
Software [Member]      
Fixed assets useful life 3 years