XML 12 R1.htm IDEA: XBRL DOCUMENT v3.22.0.1
Cover Page - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2021
Feb. 25, 2022
Jun. 30, 2021
Cover [Abstract]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2021    
Current Fiscal Year End Date --12-31    
Document Transition Report false    
Entity File Number 001-35791    
Entity Registrant Name Northfield Bancorp, Inc.    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 80-0882592    
Entity Address, Address Line One 581 Main Street,    
Entity Address, City or Town Woodbridge,    
Entity Address, State or Province NJ    
Entity Address, Postal Zip Code 07095    
City Area Code 732    
Local Phone Number 499-7200    
Title of 12(b) Security Common Stock, par value $0.01 per share    
Trading Symbol NFBK    
Security Exchange Name NASDAQ    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
ICFR Auditor Attestation Flag true    
Entity Shell Company false    
Entity Public Float     $ 766.5
Entity Common Stock, Shares Outstanding   48,935,337  
Documents Incorporated by Reference Certain portions of the registrant’s Definitive Proxy Statement (the 2022 Proxy Statement) for the 2022 Annual Meeting of the Stockholders to be held May 26, 2022, will be incorporated by reference in Part III. The 2022 Proxy Statement will be filed within 120 days of December 31, 2021.    
Amendment Flag false    
Document Fiscal Year Focus 2021    
Document Fiscal Period Focus FY    
Entity Central Index Key 0001493225