Document and Entity Information - shares
9 Months Ended
Sep. 30, 2019
Nov. 04, 2019
Cover [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 30, 2019  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q3  
Entity Registrant Name Benefitfocus,Inc.  
Entity Central Index Key 0001576169  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Current Fiscal Year End Date --12-31  
Entity Filer Category Accelerated Filer  
Entity Shell Company false  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Common Stock, Shares Outstanding   32,739,796
Title of 12(b) Security Common Stock, $0.001 Par Value  
Trading Symbol BNFT  
Entity Incorporation, State or Country Code DE  
Security Exchange Name NASDAQ  
Entity File Number 001-36061  
Entity Tax Identification Number 46-2346314  
Entity Address, Address Line One 100 Benefitfocus Way  
Entity Address, City or Town Charleston  
Entity Address, State or Province SC  
Entity Address, Postal Zip Code 29492  
City Area Code 843  
Local Phone Number 849-7476  
Document Quarterly Report true  
Document Transition Report false